A History of the UCL Physics and Astronomy Department from 1826 - 1975

The College was formally constituted as the University of London in a Deed of Settlement signed on 11 February 1826. It was established to provide higher education for people denied access to Oxford or Cambridge University, and to afford an opportunity for the study of subjects neglected at the two universities.

The first sketch of the courses to be offered appeared in the Prospectus of May 1826. A list of the professorships was published in The New Monthly Magazine in August 1826, and it appeared in The Morning Chronicle in December 1826 as an advertisement for applicants. (B.53). The first appointments to the professoriate were made by the College Council in July 1827. The Council minutes of 6 July 1827 contains the Education Committee's list of the most eligible candidates for their respective professorships, including the Rev. Dr. Lardner for Experimental Physics, and on 12 July 1827, the Rev. Dr. Dionysius Lardner LL.D., F.R.S.L. & E. of Trinity College Dublin, was elected to the Chair of Natural Philosophy and Astronomy. It has been said that Lardner owed his appointment to the influence of Henry Brougham, who assured him that he might expect to earn £1200 a year in fees. (B.39,175). Brougham was a Scot, one of the founders of the Edinburgh Review, who moved to London, becoming a M.P. in 1820 and Lord Chancellor in 1830. A campaigner for reform, especially in education, he became associated with George Birkbeck and the Mechanics' Institutes, and founded the Society for the Diffusion of Useful Knowledge in 1826. It was largely through his efforts that the dream of a university in London of Thomas Campbell, the Scottish poet, became a reality.

Lardner, the son of a Dublin solicitor, was born on 3 April 1793 and educated for the law, but disliking the work, he entered Trinity College and graduated B.A. in 1817, M.A. in 1819, LL.B. and LL.D. in 1827. He won prizes in logic, metaphysics, ethics, mathematics and physics, and was awarded a gold medal for a course of lectures on the steam engine, delivered before the Royal Society of Dublin and published thereafter. Having taken holy orders, he nevertheless devoted himself to literary and scientific work, making a reputation at Dublin as a contributor to the Edinburgh Review, the Encyclopaedia Edinensis, and the Encyclopaedia Metropolitana for which he wrote the treatise on algebra. Among his works were two books, one being a System of Algebraic Geometry, treating the geometry of plane curves, 1823; the other, An Elementary Treatise on the Differential and Integral Calculus, 1825. (D.N.B.).

Although no date was specified for the commencement of his duties, Lardner began to consider what apparatus would be required for his course and, on 17 July 1827, the Council in response to a letter from him authorised Drs. Birkbeck and Gregory to confer with him concerning the apparatus and his renumeration prior to the opening of the university. On 13 September the Education Committee approved payment of £200 to him for having purchased his first batch of apparatus, and on 11 October Leonard Horner, the Warden, informed the Council of Lardner's request to hire rooms for the reception of the apparatus and the performance of experiments during the ensuing year. The Council authorised Horner on 5 November to conclude the agreement for renting a house in Percy Street for this purpose; it also received and approved the offer of Mr. Francis Watkins, instrument maker, to be the honorary Curator or Inspector of the instruments and apparatus without any obligation to purchase apparatus from him. Moreover on 17 November the Council accepted the report of the Apparatus Committee that Lardner should be paid at the rate of £300 p.a. from 1 August 1827 so long as he should thus be employed.

Museum of Natural Philosophy

Lardner's introductory lecture, 'A Discourse on the Advantages of Natural Philosophy and Astronomy as part of a general and professional education', was delivered on 28 October 1828 to a packed audience, and was reported in the next day's edition of The Morning Chronicle as a sensational success. (B.131). In the preface to the published lecture (D.L.U.iii-iv) Lardner refers to a second lecture "devoted to the exhibition of the splendid Apparatus which has been provided for this class, and to the explanation of its uses and advantages in the business of instruction." He then states a "few particulars respecting it."

The apparatus is divided into four classes:

1. "instruments of philosophical investigation, such as Air-pumps, Balances, Electrical and Galvanic machines, and apparatus for experiments in all parts of physical science - equal, if not superior to any collection in these kingdoms."
2. "Working Models of machines, on a scale adapted for exhibition in a large theatre, to a class as numerous as that which may be expected in the University of London."
3. "It often happens that an instrument of which the use and application are to be taught, is too delicate for the rough manipulation of the lecture-room, and even though it should be produced, its parts might be too minute to be shown advantageously to a class. This remark applies very generally to instruments of philosophical observation, but more especially to those used in the departments of Astronomy and Geodaesy. In these cases well executed Models in Wood have been prepared, in which all the usual adjustments and minuter parts are exhibited on a larger scale and of less delicate construction."
4. Sectional Models. "The construction of these instruments is a subject to which Dr. Lardner has given considerable attention, and he hopes that they are now brought to a state of perfection, which entitles them to be considered the most powerful instruments of instruction which modern times can boast."

The accounts for the year ending 31 December 1827 record that £303:11:0 was spent on apparatus and £82:0:8 as the balance for the rent of the Percy Street house, part of which was lent to the Society for the Diffusion of Useful Knowledge. In the following three years Lardner spent £1077:9:4, £700:4:5, and £237:2:6 respectively on his museum, making a grand total of £2358:7:3 by the end of 1830. The first University of London apparatus book lists 486 items comprising the museum, the first 406 items being recorded in ink and most of them including the name of the maker, the delivery date and the cost. The first item, the Bramah Press, was delivered on 26 November 1827 and cost £35, and the last item is drawings of Mars, Jupiter and Saturn. Wood records that "much of this apparatus survived until 1930, or thereabouts, and some was still used in the Intermediate lectures at that time. The rest was stored under the seating of what was then the Large Theatre (below the General Library) and was in part destroyed in a small fire, which burnt also some of the seating in the theatre one Sunday afternoon in or about that year. Much of what remained was lost during the 1939-1945 war - probably stolen, bit by bit, for its metal content; a little is still preserved in the Department." (W.3-4). Some of the surviving pieces continued to be used in the Intermediate and 1st. M.B. courses until they were discontinued in the mid-fifties. At the exhibition to commemorate the sesquicentenary of the college from 9-18 May 1978 there were displayed the Apparatus Book and the following pieces of apparatus:- Magdeburg Hemispheres (1827); Model of Screw, Magnets to rotate about electrified wires, Double Cone and Tracks, Top of an Atwood's Machine (all 1828); a Superior Glass Prism and a Large Double Convex Lens (1829). (Catalogue; U.C.L. Past and Present 1828-1978). This lens was borrowed by Faraday in 1844 when he was carrying out his experiments on light and magnetism; at the time of the exhibition it was still being used in the department to demonstrate lens aberrations. In September 1980 almost all of what was left and other rarely used pieces were donated to the Science Museum for its new Science Teaching Collection on the understanding that they would be made available to the College for special exhibitions and similar functions.

When the College was ready for occupation in 1828 the department was allocated the semi-circular theatre on the first floor of the South Wing, together with two rooms between the theatre and the main building for the apparatus. (B.172). It is worthy of note that at the meeting of the Building Committee on 16 October 1827 Lardner reported that Mr. W. Wilkins, the architect, had informed him that a sum of £500 had been included in the contract price for certain work to be executed in the dome for the reception of astronomical instruments and that he (Lardner) considered the sum could be saved since they would be useless in such a place. On 29 May 1828 following Lardner's suggestion, Mr. Kirby was appointed as his assistant for the care of the apparatus and for attending him during lectures at a salary of £75 per annum.

The Lecture Courses

In the Second Statement issued by the Council in November 1828 explaining the plan of instruction, two regular courses are proposed (i) for the Junior Class every day except Saturday from 3.30 to 4.30 p.m., comprising c.170 hours of instruction at a fee of £7, (ii) for the Senior Class on Tuesday, Thursday and Saturday from 11 a.m. to noon, comprising c.100 hours of instruction at a fee of £6. The syllabuses are given in detail, occupying almost 12 pages; that for the Junior Class on Elements of Mechanics is subdivided into Statics, Dynamics, Hydrostatics-Hydrodynamics (including capillary attraction), and Pneumatics; the headings for the Senior Class are Light, Astronomy, Geodaesy, Heat, Electricity and Magnetism.

However the Report of the Distribution of Prizes and Certificates of Honours for the 1828-9 session records that since no regular class of academical students had presented themselves the lectures were adapted principally to students whose knowledge of elementary mathematics was very limited. Lectures were accordingly delivered three times per week embracing the principal parts of Mechanics, Hydrostatics and Pneumatics. Additional lectures were given twice a week to a few students having some mathematical attainment; these students took an examination and equal prizes were awarded to two of them, namely R. L. Powell of London and Count Calhariz of Lisbon. A very large number of persons of all ages from fifteen to thirty attended several of the courses, as many as one hundred attending one on mechanics. In the 1829-30 session lectures were given to both the Junior and Senior classes and at the close of the session a general examination was held. No prizes were given in the Senior class, but Certificates of Honour were awarded to the two aforesaid gentlemen. In the Junior class the first Certificate and Prize was awarded to Thomas Thomson of Clitheroe and a Certificate was also awarded to Wilton George Turner of London. Lardner also gave three courses of popular lectures during this session on Monday and Thursday evenings from 7.30 to 8.30 p.m.; these were 12 lectures on Astronomy, 18 on Mechanics and Hydrostatics, followed by 18 on Pneumatics, Optics and Heat, detailed syllabuses being given in the 1831 Calendar.

The Midsummer Examination set in 1830 for the Junior Class is reproduced in this Calendar. It consists of 37 questions, some of which are linked e.g., 1-3 on the experimental, geometrical, and analytical proof respectively of the parallelogram of forces; 18-22 on the conditions of equilibrium respectively in a train of wheelwork, a wheel with a double axle, the inclined plane, the different system of pulleys, and the wedge and screw. The last question is "Prove that a solid immersed in a fluid loses the weight of the fluid which it displaces, and imparts so much weight to the fluid." In Lardner's last complete session 1830-31 the First Certificate and Highest Prize was awarded to James Chance of Birmingham, the son of William Chance, one of the founders of the glass-making firm. Seventh Wrangler at Cambridge in 1837, he became a partner in the firm in 1839 and initiated the lighthouse work for which it became renowned; later a knighthood was conferred upon him.

Early in January 1830 Lardner was informed that his salary would cease on 30 October next owing to the College's limited funds and that his renumeration would be restricted to two-thirds of the fees derived from his classes. This prompted a response from him which the Council construed as a letter of resignation; however he disclaimed any wish to quit or to give offence by the terms of his letter. His affairs continued to come before the Council and on 8 May a motion to remove him from office was only lost on a technicality, namely the majority falling short of that specified in a bye-law. There followed in July the imposition of ten conditions on the continuation of his professorship, and a guarantee of £300 for the ensuing session 1 November 1830 to 31 July 1831. Since only 8 students had enrolled for his class by 3 November 1831, the Committee of Management resolved that the course should be divided into two parts, the first consisting of three lectures per week on Astronomy from 30 November to the Christmas recess at a fee of £1. Lardner was absent on 31 November apparently owing to an unexpected summons to Dublin to give evidence in a lawsuit - he had tendered his resignation in a letter dated 30 November owing to the inadequate renumeration afforded by his class!. Needless to say his resignation was accepted by the Council on 3 December; the vacant chair was advertised, applications being required by 31 December. The class was abandoned and the fees were returned to the students who had entered for it.

Bellot writes "He made up in contemporary notoriety what he lacks in more lasting fame. Lardner, his apparatus, his courses, and his salary, caused more pother than almost any other topic in the early history of the college, and he occupies a very disproportionate amount of the early Minutes of the Sessions of the Council. He figured equally prominently in the public eye. He was a very successful popular lecturer, and a man of unbounded energy and great literary activity - he moved more freely than any other of the professors in the fashionable literary society of his time. - His public lectures were well attended and highly appreciated. And his apparatus won favour where the more austere learning of some of his colleagues failed. It gave notoriety to his lectures and afforded a diversion to the aristocracy." In 1831 the guarantees of professorial salaries ceased owing to lack of funds and in 1833 the Council was rescued by the professors who guaranteed an income of £3181 for the 1833-4 session. Meanwhile the financial plight of the College is illustrated by the following quotation of Sydney Smith: "I understand that they have already seized on the air-pump, the exhausted receiver, and galvanic batteries; and that the bailiffs have been seen chasing the Professor of Modern History round the quadrangle." (B.131,176-8).

His most memorable literary work is the Cabinet Cyclopaedia which he edited in 133 volumes between 1829 and 1849, securing some of the most eminent writers of the day. Lardner himself contributed the treatises on hydrostatics and pneumatics, arithmetic and geometry, and collaborated with Captain Kater on mechanics, and with C. V. Walker in those on electricity, magnetism, and meteorology. In The Yellowplush Papers Thackeray satirising Lardner writes, inter alia, 'It's the litterary wontherr of the wurrld,' says he; 'sure your lordship have seen it ; the latther numbers ispicially - cheap as durrt, bound in gleezed calico, six shillings a vollum. The illusthrious neems of Walther Scott, Thomas Moore, Docther Southey, Sir James Mackintosh, Docther Donovan and meself, are to be found in the list of contributors. It's the Phaynix of Cyclopajies - a litherary Bacon.' (B.133). Thackeray also satirised him as Dionysius Diddler in the Miscellanies. There is a delightful caricature of him as Dion Lardner in Fraser's Magazine for August 1832, this being reproduced by Harte and North (49;35). Dr. Lardner's Cabinet Library started in 1830 but was discontinued in 1832 after nine volumes had appeared. He also edited the Edinburgh Cabinet Library which ran to thirty-eight volumes, chiefly devoted to history, travels, and biography, between 1830 and 1844.

Lardner is credited with 11 papers in the Royal Society Catalogue, the third and fourth (each short) on lunar theory and on certain properties of vapours being published in the Proceedings in 1831 and 1832 respectively. The last three were communicated to the Royal Astronomical Society in 1852; they were entitled 'On the Uranography of Saturn', 'On the Classification of Comets, and the Distribution of their Orbits in Space', and 'On Certain Results of Laplace's Formulae'.

He was first married in 1815 to Ceclia Flood and they had three children before separation by mutual consent in 1820. He had an affair with Mary, the wife of Captain R. Heaviside, a cavalry officer, and eloped with her in 1840. Heaviside was awarded £8000 in an action for seduction and his marriage was dissolved in 1845 by an act of parliament. Meanwhile Lardner went to the United States and Cuba on a lecturing tour earning, it is said, £40,000. Returning to Europe in 1845 he settled in Paris and his own marriage being dissolved in 1849, he married Mary Heaviside, by whom he had two daughters.

Lardner visited London in 1851 and reviewed the Great Exhibition for The Times. He was reputed to be the Paris correspondent of The Daily News. During his residence in Paris he wrote extensively on natural philosophy and astronomy. The Museum of Science and Art, a collection of works on various branches of science, especially in relation to common life, was launched in 12 volumes in 1856. He died in Naples in 1859. There is an extensive biography, including a comprehensive bibliography, in the Dictionary of National Biography.

The Rev. William Ritchie Ll.D., F.R.S., who had applied for the Chair of Mathematics in 1827, succeeded Lardner on 7 January 1832. Born in c.1790, he was educated for the Church of Scotland and licensed to preach, but abandoning the church for the teaching profession, he became Rector of the Royal Academy at Tain on Dornoch Firth in Ross and Cromarty. By extreme thriftiness he saved enough money from his small annual stipend to attend a course of lectures by Thénard, Gay-Lussac and Biot in Paris, and to provide a substitute for the performance of his duties at the academy during his absence.

His skill and originality in devising and performing experiments with the simplest materials soon attracted the attention of distinguished philosophers including Sir John Herschel, who communicated to the Royal Society his papers 'On a new Photometer', 'On a new form of the Differential Thermometer', and 'On the Permeability of transparent screens to Radiant Heat'. While still Rector of the Royal Academy he gave a course of probationary lectures at the Royal Institution in the Spring of 1829 and he was appointed Professor of Natural Philosophy there in 1831 at an annual salary of £50. (Phil. Mag. xii, 275-6).

Resumption of Teaching

Ritchie formed a new class of 12 students and according to the relevant Report of the Distribution of Prizes he "continued to lecture with a zeal and perseverance for which the University has reason to be highly grateful to him. Dr. Ritchie bears a strong testimony to the good conduct and diligence and improvement of his class." History was made in this session in May 1832 when two ladies, Mrs. J. P. Potter and Miss Rogers, attended his juvenile course of 6 lectures on electricity. This historical development followed the Council's resolution on 7 April 1832 that ladies be admitted on payment of the fee (£1) and with the nomination of a proprietor. Mrs. Potter's husband, a clergyman, also attended the course; both he and their young son, who became a distinguished surgeon at the hospital, were registered for the course in natural philosophy. (B.367).

In the following 1832-3 Session the number of students in his regular classes rose to 38; there were two distinct courses throughout the session (i) Physical and Experimental in which the phenomena of nature were explained and illustrated by experiments in a manner intelligible to any attentive observer, (ii) Experimental and Mathematical in which the same phenomena were exhibited but their laws and the underlying theories were demonstrated by the strict processes of mathematical reasoning. Ritchie also gave two short courses of a more elementary and popular character, which were attended by several ladies; c.100 boys in the higher classes of the Junior School attended the second short course.

For the 1833-4 Session (i) was advertised as being peculiarly adapted to students of medicine and young men whose professions do not require an extensive acquaintance with mathematics. Three divisions were listed (a) General Properties of Matter; Statics; Mechanics; Dynamics; Astronomy: (b) Hydrostatics; Hydraulics; Pneumatics; Sound; Heat; Steam; Steam Engine; (c) Common and Voltaic Electricity; Magnetism; Electro-Magnetism and Magneto-Electricity; Relations of Heat and Light; Optics. The fee for the course of three lectures per week was £7; however any division could be attended separately, the fee for each division being £2:10s. The Experimental and Mathematical course embraced the same subjects, the fee for the whole course of three lectures per week being £7. In each of the courses viva voce examinations and written exercises were prescribed.

Ritchie also delivered a course of lectures on Civil Engineering embracing the Application of Statics to the Equilibrium of Arches and Domes; the Pressure of Fluids; Naval Architecture etc.; it was illustrated by Drawings and Models of Bridges, Domes, Locks, Steam Engines etc. Commencing in February, it continued for three months at a fee of £3:10s. There was no Department of Engineering at this time despite the fact that it had been intended to establish one at the outset and J. Millington, then Professor at the Royal Institution, was indeed appointed to the Chair. Incidentally he had applied for the Chair of Natural Philosophy almost four months before Lardner. However he resigned from his chair before the university opened owing to the failure of the Council to guarantee a salary of at least £400 per annum. The chair being unfilled, only occasional lectures in engineering were advertised. The proposal to fill the chair was revived in 1833 but Ritchie objected on the grounds of an invasion of his province and consequently a menace to his salary. Hence special courses on Civil Engineering were given by Ritchie and his successors, supplemented by courses from the Professors of Mathematics and of Chemistry, and the chair was not filled until 1841. (B.135-6). Ritchie's course on Civil Engineering in the 1835-6 Session was reported at the Distribution of Prizes and Certificates of Honours "to have been well attended by gentlemen who on account of the practical tendency of their pursuits might not otherwise have come to the University."

In the Midsummer Examinations of 1836 Ritchie set two papers for each of his regular classes. Question 6 of the forenoon paper for the Experimental and Physical Course reads "State a few of the more striking analogies between light and sound, and give your reasons for adopting the undulatory theory of light". Wood commenting on this question, recalls Ritchie's attendance at the lectures of Biot, a fervent supporter of the corpuscular theory of light. (W.9). Question 8 of the corresponding paper for the Experimental and Mathematical Course reads "If a body revolve round another as its centre of attraction, it is required to demonstrate that the radius vector will describe areas proportional to the times". It is interesting to note that his second paper for the Experimental Class in February 1837 contains the questions
10 "Describe the processes of reasoning called Inductive, Deductive, and Analogical, and give examples" and
13 "Demonstrate the existence of a First Cause, or of one altogether different from any of the powers of matter with which you are acquainted."
His last papers set in the Summer of 1837 for this class contained 19 questions; in the first paper there occurred "Describe the nature of spherical and chromatic aberrations, and explain the method of correcting both in the construction of an achromatic object-glass" and "Describe the Torsion galvanometer, and explain its mode of action and uses", and in the second, "Describe the properties of steam on which the condensing steam-engine is founded; describe the various parts of that engine with reference to a diagram, and state the improvements of Watt and others", "Determine the specific gravity of this piece of flint-glass by the hydrostatic balance, and also by the hydrometer" and "Determine the specific gravity of this liquid by means of the same instruments". It is interesting to speculate whether the last two questions involved the performance of simple experiments by the students.

The Apparatus

In August 1831 the Committee of Management had considered whether the services of Kirby as Curator of the Apparatus were necessary, but after examining him in person, it was decided that they were required, and in July 1832 Messrs. Watkins and Hill were informed that their use of the title of Curators of the Apparatus was not recognised by the university. Ritchie attended the meeting of the Committee on 7 November 1832 praying for an allowance of £30 for the construction of apparatus under his inspection in view of deficiencies for illustrations in Light, Sound, and Heat; he was given leave to draw £10 before Christmas. On Ritchie's recommendation Francis Kerby (the alternative spelling of the surname in the minutes), son of the late assistant, was appointed Assistant to the Professor and Curator of the Apparatus on 25 November 1835. He was required to keep the apparatus in repair, to make any new piece of apparatus needed for experimental research or illustration, and to attend the lectures when required; moreover he was expected to superintend the working of the stills in the Medical Department when required, all for the same salary of £75 p.a. paid to his father from 1828. Apparently one of the rooms allocated to the department for the storage of apparatus was relinquished to the School (see p.12) owing to a fire destroying the School's accommodation in the Great Hall and the rooms below it in October 1836. (B.p.174). It appears from the accounts that Ritchie was only required to spend £53:15:8 on apparatus during his tenure of the chair, which ended on 15 September 1837 when he died of a fever caught on holiday in Scotland.

Ritchie's Researches

In the Royal Society Catalogue Ritchie is credited with 44 papers, the first 23 being published between 1820 and 1831. These include the work for which he is best known, namely the wedge photometer, the differential air thermometer, the torsional properties of glass fibres, and his torsion galvanometer. While at College he published two text-books, one on Geometry (1833; 3rd.edition 1853), the other on Differential and Integral Calculus (1836; 2nd.edition 1847). His experimental researches on the electric and chemical theories of galvanism, on electromagnetism and voltaic electricity were more remarkable for the ingenuity shown in the contrivance and execution of the experiments than for their theoretical insight. Wood in his review of Ritchie's work concludes with the last paper printed in abstract (Proc. Roy. Soc. 1837, 483) "Ritchie started by stating that his experiments had shown that Ohm's law for the conducting powers of wires is true only for feeble currents and that for the same metal the conducting power does not vary as the length. Then he states that he had found that the heat developed in the same conductor is proportional to the square of the current and that, in wires of the same diameter conducting equal quantities of electricity, the heat is inversely as the conducting power or directly as the resistance. Had he lived he might perhaps have corrected the errors in the first part of the paper and given a clear statement of Joule's law". (W.10-12).

Ritchie carried out an extensive series of experiments on the manufacture of glass for optical purposes and a Commission was appointed by the Government with a view to their further prosecution financed by public funds. A telescope of 8 inches aperture was made by Dolland from Ritchie's glass on the Commission's recommendation but its performance did not warrant further expenditure on the project. His Royal Society obituary concludes "--- though the traces of an imperfect and irregular education are but too manifest in most of his theoretical researches, yet he must always be regarded as an experimenter of great ingenuity and merit, and as a remarkable example of the acquisition of a very extensive knowledge of philosophy under difficulties and privations which would have arrested the progress of any person of less ardour and determination of character." (Phil. Mag. 276).

On 22 November 1837 the Council resolved unanimously that Mr. James Joseph Sylvester be appointed as Ritchie's successor. He had been expelled from the college at the age of fourteen for taking a table-knife from the refectory with the intention of stabbing a fellow student who had incurred his displeasure. (B.186). Second Wrangler in the Mathematical Tripos in 1837, he came to the College at the age of 23 owing to his academic career at Cambridge being blocked by his Jewish faith. In the Notes and Materials for the History of U.C.L., edited by W.P.Ker, there is written in the section on Applied Mathematics and Mechanics "In Professor Sylvester's hands Natural Philosophy, it is perhaps needless to say, was Applied Mathematics in the Cambridge sense, and his occupation of the chair is sufficient evidence, were any needed, that the chair of Applied Mathematics is not a creation of the year 1864, but a co-heir with the chair of Physics in the patrimony of the old chair of Natural Philosophy." (K.59). Although this applied to his Systematic Course, it should be noted that in his Experimental and Descriptive Course "he hoped to include at least the principal parts of the following subjects in the course of one Session: Dynamics, Statics, the principles of Machinery, Hydrostatics, Pneumatics, Hydraulics, Optics, Astronomy, Light, Heat, Theory of the Steam Engine, Sound, Electricity, and Magnetism"; he also continued to give the lectures on Civil Engineering. He expected to resort to experimental and other means of illustration, so far as was possible, both in the Systematic and Popular Courses.

In 1839 the Schoolmasters' Classes were introduced in order to enable masters of unendowed schools and ushers to attend evening courses in Greek, Mathematics, Latin, and Natural Philosophy; 33 entered for the four classes, 3 for mathematics alone, one being Todhunter. Sylvester's course of 10 lectures started in the week after Easter. (B.169). According to Bellot "He was an inspiring but baffling teacher. Consumed by whatever engaged his understanding at the moment, he could pay attention to nothing else, and the combination with this abandonment of a peculiarly acute mind, which could never pass over a difficulty or accept anything until it had made it its own, rendered him quite incapable of the methodical pursuit of a predetermined course." (B.134).

During his occupancy of the chair the amount spent on Apparatus rose from £2413:17:4 to £24558:14:2. In February 1840 a Mr. Minasis, who had apparently succeeded Francis Kerby, resigned as Curator of the Apparatus and was paid a bonus of £20 mainly for his extra work during the previous session. On Sylvester's recommendation Mr. Watts, a student in the Schoolmasters' Class, was engaged in March as Assistant Keeper of the Apparatus for one month on trial at £5, this being a temporary measure. Mr. John Day, a journeyman telescope maker, replaced Mr. Watts in April on trial for one month at the rate of £60 per annum, and in July 1841 it was decided to pay him weekly, an extra half a crown per week being added in consequence of his good conduct.

In May 1841 Sylvester announced his candidature for the Professorship of Pure Mathematics in the University of Virginia and in August he resigned his chair at College to take up that appointment. In accepting his resignation the Management Committee instructed the Secretary to write to Sylvester expressing regret at the loss of his services and their wishes for his prosperity. Incidentally he only stayed at the university six months since his views on slavery were incompatible with those of his colleagues.

While at College, the first of his 112 publications listed in the Royal Society Catalogue appeared in the Philosophical Magazine (xi,1837; xii,1838), namely, 'Analytical developments of Fresnel's optical theory of crystals', and he was elected a Fellow of the Royal Society in 1839 at the early age of 25. The Society awarded him the Royal medal in 1861 and the Copley medal in 1880. In the Dictionary of National Biography he is recorded inter alia " as one of the foremost mathematicians of his day.

In brilliancy of conception, in fluency and richness of expression, Sylvester has had few equals among mathematicians. But his strength was not accompanied by restfulness or caution. He worked impulsively and unmethodically. As soon as a new idea entered his brain, he at once abandoned himself to it, even if it came upon him while lecturing or writing on another theme. Consequences and collateral ideas crowded upon him, and all else was thrust aside. He was wont to write with eager haste in a style as stimulating as it was excited, in flowery language enriched by poetical imagination, and by illustration boldly drawn from themes alien to pure science. In oral exposition he riveted attention.

He was great as a maker of mathematicians no less than of mathematics. He imparted ideas and made them fascinating, thus leading others on to employ more prosaic powers in pursuing lines of investigation to which he introduced them. In youth, he was one of the foremost in leading the revival of mathematical activity in England. Later in life when in Baltimore, where he founded the American Journal of Mathematics, he brought into being a school of mathematicians which has become an object of universal admiration. Later still, he exercised a like stimulating influence as professor at Oxford.

Sylvester's writings, when collected in a succession of quarto volumes, will, it is estimated, cover some 2500 pages. They are scattered through journals and volumes of transactions covering sixty years. Among these are the Philosophical Transactions and Proceedings of the Royal Society and the Messenger of Mathematics, in which last appears his latest paper, dated 12 February 1897, and annotated less than three days before his death." A photograph of Sylvester is reproduced by Harte and North (100;67).

On 12 October 1841 a special meeting of the Council was summoned to receive the report of the Senate on the applications and testimonials of the candidates for the vacant chair. It was resolved unanimously that Mr. R. Potter be elected, the Council reserving to themselves the right to institute at any future period, if it shall be expedient, a special Professorship or Lectureship in Practical Mechanics of the nature of that formerly held at Cambridge by the late Professor Farish. In his letter of acceptance of the chair Potter observed that he considered the latter professorship to be one of Machine Making and Manufacture, and not interfering with the theory of Machines or Mechanics as a science.

Potter was born in Manchester in 1799 and educated at Manchester Grammar School from 1811 to 1815. On leaving school he worked in a Manchester wharehouse without success, his leisure time being devoted to scientific pursuits, especially the study of optics and chemistry, in which he was encouraged by Dalton (the founder of modern atomic theory), who at one time was his tutor. In 1830 he wrote an article on metallic mirrors in Brewster's Science Journal. At the British Association meetings in 1831, 1832 and 1833, he read three, two and three papers respectively, and the attention given to these papers induced him to prepare for university entrance. He studied classics under a private tutor and obtained a scholarship to Queen's College, Cambridge, graduating B.A. in 1838 as sixth Wrangler. In January 1839 he was elected a Foundation Fellow of his College, succeeding to the medical scholarship and obtaining the L.R.C.P. qualification, but never practising medicine, and in 1841 he proceeded to the M.A. degree. At the time of his election to the College chair he had published 34 of the 47 papers cited in the Royal Society Catalogue. (D.N.B.).

In April 1842 Potter was granted a sum not exceeding £25 to purchase instruments to illustrate his lectures on optics. Apparently lectures were delivered to an experimental class and to both a junior and a senior mathematical class. He set two examination papers to each of the classes in the Summer of 1842. The papers for the experimental class were headed (i) Hydrostatics, Hydrodynamics, Heat, Pneumatics, and (ii) Optics Geometrical and Physical - Electricity - Astronomy, there being sixteen questions on each paper. Those for the junior mathematical class were headed (i) Hydrostatics, Hydrodynamics and (ii) Optics, Astronomy, there being fourteen and sixteen questions respectively on the papers; the headings for the senior class only differed by the inclusion of Dynamics in the first paper, which contained fifteen questions as distinct from fourteen on the second paper.

Potter, in a letter dated 1 November 1842, announced his intention to end his lectures next Easter, having accepted the Chair of Mathematics at King's College, Toronto. Professor P. Kelland F.R.S., Professor of Mathematics in the University of Edinburgh, wrote to Potter on 5 November 1842 offering to finish Potter's course after his departure in April. The Council noted Kelland's letter on 14 January 1843 and accepted his offer on 4 February 1843, Kelland being informed that in the event of his candidature for the vacant chair his appointment to complete Potter's course would neither count for nor against him! Kelland received £84:16:3 for his services.

The vacancy was advertised, four applications being received. On 10 June the Council resolved that it was not expedient to endow the chair, and on 17 June 1843 after a ballot on the respective merits of a Mr. Cook and Mr. Charles Brooke B.A., formerly of St. John's College Cambridge, it was resolved that the latter be appointed, the Council again reserving the right to institute the special appointment in practical mechanics. Brooke accepted the chair on 21 June and by mid-July had presented the Council with a list of new apparatus required and repairs to some existing pieces; he received permission to spend up to £30, this sum being increased by £15 in September for an alteration to the Bramah press. (Incidentally on 27 March 1844 the Management Committee gave permission to Mr. Marshall, then Sub-Curator of the Museum, to use two pieces of apparatus in an external lecture that evening, and on 29 May gave Brooke permission to lend Faraday the large mirror and lens - the lens referred to on p.2).

Brooke soon ran into trouble with the students of the senior mathematical class and they wrote on 13 November "announcing their intention to withdraw from the lecture room finding it impossible to make any progress under the tuition of the Professor in consequence of his neglect of the higher parts of Analysis during a period of 14 or 15 years in favour of other professional pursuits and enquiring what compensation for the fees the Council would allow them."

However the students of the experimental class signed a paper signifying their approval of the professor's lectures. These and other pertinent letters and papers came before the Senate at its meeting on 22 November in which De Morgan (Professor of Mathematics) and Key (Headmaster of the School and Professor of Comparative Grammar) featured prominently, the outcome being the unanimous adoption of a resolution that Brooke should be requested to resign his chair forthwith. The Council considered the matter at its meeting on 25 November and also a letter of that date from Brooke tendering his resignation, but expressing his wish to continue the experimental course until the end of the session and his willingness to instruct the junior mathematical class as long as it suited the college. It was resolved unanimously that Brooke's resignation be accepted; that he be requested to continue the lectures to the experimental class until a successor be appointed; and that De Morgan be requested to instruct the mathematical class to the end of the session.

On 2 December the Council read two letters of that date (i) from Brooke forwarding a paper signed by 27 students of the experimental class expressing their desire that he should continue their course; (ii) from Mr. J. Chapman of that class asking to be allowed to withdraw from the class and attend a similar course next session without payment of an extra fee - a request not granted! The Council resolved at its meeting on 13 January 1844 to advertise the vacant chair, and approved De Morgan's offer to give the course of lectures on natural philosophy to the schoolmasters' class as well as his own on mathematics.

Charles Brooke was born on 30 June 1804, the son of the well-known mineralogist, Henry James Brooke. He went to St. John's College Cambridge from Rugby School, becoming twenty-third Wrangler in 1827, B.M. in 1828, and M.A. in 1853. His medical training was completed at St. Bartholomew's Hospital, passing the College of Surgeons on 3 September 1834 and becoming a Fellow of that College on 26 August 1844. He was a surgeon at the Metropolitan Free Hospital and the Westminster Hospital, resigning the latter appointment in 1869. His invention of the "bead suture" was a great advance in the scientific treatment of deep wounds.

On 4 March 1847 he was elected to the Fellowship of the Royal Society. He became President of both the Meteorological and the Royal Microscopical Societies, and invented those self-recording instruments which were adopted at the Royal Observatories of Greenwich, Paris and other meteorological stations; his invention gained the premium offered by the government and a Council medal from the jurors of the Great Exhibition.

An account of this work was published in the British Association Reports from 1846 to 1849, and in the Philosophical Transactions of 1847, 1850, and 1852. His study of the theory of the microscope led to his improvement of the methods of facilitating the adjustment of the lenses and the illumination of the specimens; they were applied to the investigation of some of the best known test-objects of the microscope. He wrote twelve papers on physical topics, including those on the aforesaid instruments. He edited a revised and greatly enlarged fourth edition of Dr. Golding Bird's 'Elements of Natural Philosophy' after Bird's death in 1854, followed by a fifth edition in 1860, and in 1867 he entirely rewrote the work for the sixth edition. He died at Weymouth on 17 May 1879.(D.N.B.).

On 24 February 1844 the Council being informed that Potter would be a candidate if the chair were moderately endowed, resolved that he be informed of their willingness to appoint him on the basis of a fixed allowance of £150 per annum in addition to his share of the fees and the whole income arising from the Schoolmasters' class provided he accepted before 1 June and gave an assurance that he would occupy the chair for at least three years. Potter's reply contained terms unacceptable to the Council so the chair was offered to Kelland on the original terms. Kelland sought time to reply, expressing his belief that Potter was willing to accept the original proposals; this proved to be the case and on 1 June Potter was appointed Professor of Natural Philosophy and Astronomy, the last holder of that title. Thus was reversed the Council's decision of 10 June 1843 not to endow the chair. When the Senate was informed of Potter's reappointment with an endowment, it passed a resolution thanking the Council for the "prompt measures taken to secure the services of such a well-qualified gentleman; moreover it fully saw the necessity of departing from the rules owing to the shortage of time."

No Calendar was issued after 1831 until 1853 when Potter is recorded as giving three lectures per week on each of his three courses. The subjects treated in the experimental and descriptive course are amplified in the Supplemental Prospectus of the Department of Civil Engineering and Architecture as follows:-I Mechanical Sciences. Statics: on the nature of statical forces and the modes of measuring them; the composition and resolution of forces; on their tendency to produce rotatory motion; on the finding of the centre of gravity of bodies, and its properties; the principle of virtual velocities; on the elementary machines; on the effects of friction in statical problems. These lectures are illustrated by many experiments. Dynamics: the measure of forces when they produce motion - on bodies impinging; on bodies moving by the action of accelerating and retarding forces; on the lunar and planetary motions, and tides; on the constrained motion of bodies; on the dynamical principles; on the moment of inertia in rotating bodies; on oscillation; on percussion; on motion in a resisting medium, etc. - with many experimental proofs and illustrations. Hydrostatics: the properties of fluids; their transmission of pressure; their pressure on surfaces; on floating bodies; on elastic fluids; on heat; on the hydrostatical instruments - thermometer, barometer, Bramah's press, air-pump, steam-engine, etc. - the experimental proofs are very numerous. Hydrodynamics: the form of jets of fluids; the construction of water-wheels; the properties of diverging and converging streams of air, etc. II Acoustics. III Optics, including the properties of ordinary and polarized light; optical instruments. IV Electricity, comprising electrostatics, electromagnetism, thermoelectricity, etc. V Astronomy: astronomical instruments; methods of observing; phenomena of the universe.

The junior mathematical course comprised Elementary Statics, comprehending the mechanical powers and their combinations; Dynamics, as far as variable forces; Newton's Principia, sections 1 to 3; Elementary Hydrostatics and Hydrodynamics, with the theory and use of hydrostatical instruments; the elementary parts of Optics, and the theory of optical instruments as far as the mathematical attainments of the students will permit; Elementary Astronomy. In the senior course the subjects were Analytical Statics; Dynamics, commencing with variable forces; the higher branches of Hydrostatics and Hydrodynamics; Optics; and Plane Astronomy. Examination questions were proposed to the students at the latter part of each lecture and the answers were expected to be written in the lecture-room. This was to enable Potter to direct the studies of the classes more effectively.

In January 1845 Potter set examination papers on Mechanics for each of his three classes: these were followed in June by two papers for each class, those for the experimental class on Geometrical and Physical Optics, and Astronomy, and on Hydrostatics, Acoustics and Electricity; those for the junior mathematical class on Optics and Astronomy, and on Newton and Hydrostatics; those for the senior class on Optics and Astronomy, and on Dynamics and Hydrostatics; there were sixteen questions on each paper for the experimental class and fourteen on each paper for the mathematical classes. This remained the pattern throughout except for the interchange of Astronomy and Hydrostatics on the junior mathematical papers and usually sixteen questions on each paper, all being set in June. The second paper set for the experimental class in June 1846, contrary to its title, contained three questions on heat, the middle one being "What is meant by the specific heat of a body? Show how to find the specific heats of metals, noticing the precautions to be taken in order to obtain correct results."

During his occupancy of the chair the value of the apparatus in the department increased by £359:2:3, an average of c.£12:7s per year with a maximum of £38:4:2 in the 1847-8 session. In the autumn of 1847 an iron railing was erected around the upper platform of the lecture theatre to protect the models of inventions, which had been presented to the College by the Society of Arts. (K.67). It was reported at the Management Committee's meeting on 31 July 1856 that Potter's assistant, Mr. John Botten, had been given notice of discharge at the end of the week on Potter's request and, on his recommendation, William Waddell, Driver and Gunner of Artillery, had been engaged at one guinea per week - a saving of 5s:6d a week! On 6 January 1859 the Committee sanctioned the purchase of a more powerful electromagnet at a cost of c.£20, to be kept for the more delicate and difficult experiments, since the large one purchased in 1844 had greatly deteriorated by usage and was never large enough to show the effect of magnetism on flames and in similar experiments; this purchase was approved on "the understanding that the instrument like all other articles in the Collection of Apparatus of Natural Philosophy when not in use by the Professor of that subject may be used by teachers for the instruction of classes in other departments of the College and Junior School on application to the office with an undertaking for its return in due course and uninjured." At its meeting on 17 June 1865 the Council approved a recommendation of the Committee on Finances that the assistant to the professor should no longer be paid by the College, but that one of the beadles should be placed at his service for a few hours each week, and on 11 July the Management Committee recommended that notice be given to the assistant that his services will no longer be required.

Porter writes "Potter was a keen experimentalist, as is shown by his 59 papers, chiefly in connection with Optics. He was essentially, however, a man of the previous generation and was unable to assimilate the developments which had taken place since the latter part of the eighteenth century. In connection with theories both of light and heat he belonged to the old school. The undulatory theory, which had been revised by Young and developed by Fresnel, seemed to him to be in conflict with many of his own experiments and he recurred to the corpuscular theory, with the principle of periodicity as an essential property of light. He considered the luminiferous corpuscles as flying off in surfaces, sheets or shells from luminous points, with intervals which are constant for the same colour of the solar spectrum, but which vary from colour to colour. Again, the general principle of conservation of energy was not acceptable to him. The heat produced in boring cannon (as in Count Rumford's experiments in 1798) was attributed by him to the sudden compression of the air between the tool and casting. Also, Joule's investigations on the mechanical equivalent of heat (1841-47) were considered by him to be faulty because they were performed in air." (P.4). Bellot records that "In the early 'fifties Jevons found him very dull but still a good experimentalist. By the 'sixties his incompetence had become notorious. Recalling him in 1921, Dr. Bourne Benson said: "The professor was the dearest of old gentlemen with long, silky, silver grey hair, a winning smile, and a very gentle deprecatory manner. . . But as a teacher in my day, he had one fatal defect. He was worn out, he had lost his memory and not a few of his wits. In his experimental class he was mercilessly ragged. I have seen him snowballed in his lecture-room, I have seen him sprayed. His only retort was a deprecatory gesture which meant 'How could you?'; and all he said was 'Gentlemen, gentlemen.' The apparatus was as worn out as the professor. It never did what it was expected to do. Magnetic force, for example, would be demonstrated experimentally by holding a needle to what might once have been a magnet, but had ceased to attract, whilst the professor said, 'You see it wants a little helping, gentlemen.' In his mathematical class the professor was dependent upon his book. Sometimes, ashamed of copying, he would attempt a few lines on his own, and get hopelessly involved. In despair he would return to his book and copy the conclusion at the bottom. Some unkind student would point out a non sequestur in the middle. The dear old man, with a puzzled look, would glance from the blackboard to his book and from his book to the blackboard, and then turn to his class with an air of triumph and say 'But, gentlemen, you see the conclusion is correct. It is a case of compensation of errors.' " (B.263).

The state of affairs was such that the Senate on 22 June recommended an enquiry into the condition of Potter's classes, expressing no opinion, but affirming the existence of rumours which clearly needed investigation. On 24 June the Council appointed a committee of enquiry and, on receiving its unanimous report on 1 July, resolved inter alia that an offer be made to Potter of an annuity of £150 on his retiring forthwith from the Chair of Natural Philosophy and Astronomy. This he did in a letter of 4 July, and went to live in Cambridge, surviving for the next twenty-one years on his £150 per annum, which had to be bourne by the College's current account when the receipts were barely sufficient to meet the expenses. Only in 1868 were the first steps taken to establish a Retired Professors' Fund on the basis of a donation of £1000 from Samuel Sharpe, a generous benefactor of the College. (B.356).

In his prime Potter was a competent mathematician and a good expositor on paper. He published fifty-nine or more contributions to journals and transactions of scientific societies, and he wrote the following books:- 'Elementary Treatise on Mechanics', 1846; 'Elementary Treatise on Geometrical Optics', two parts, 1847 & 1851; 'Physical Optics, Nature and Properties of Light', two parts, 1856 & 1859; and a 'Treatise on Hydrostatics and Hydrodynamics', two parts, 1859 & 1887. Porter (loc. cit.) rates the treatise on geometrical optics (founded on Coddington's Optics) as a noteworthy contribution to the subject. For him pictured in gown, notes in right hand, books under left hand, see Harte and North (107;72).

Wood cites among his old students Frederick Guthrie who took his B.A. in 1852 and was presumably the Guthrie who played so large a part in the formation of the Physical Society in 1874; W.E.A. Ayrton (1864-66) who gained prizes both in Mathematics and Natural Philosophy and became Professor of Electrical Engineering in the City and Guilds College; and E.H.Fournier d'Albe (1864-5). (W. 16).

With the retirement of Potter, the vacancy was advertised in terms of the appointment of either one or two professors, and resulted in three applications for a Chair of Mathematical and Experimental Physics; two for Mathematical Physics alone or combined with Experimental Physics; three for Mathematical Physics ; and one for Experimental Physics. After consideration of the qualifications of all the candidates, it was decided to replace the Chair of Natural Philosophy and Astronomy by separate Chairs in Mathematical and Experimental Physics. T. Archer Hirst Ph.D., F.R.S., a one-time master at the school, was appointed to the former and G. Carey Foster B.A., an old student and erstwhile assistant of Professor Williamson in the Department of Chemistry, was appointed to the latter by the Council at its meeting on 1 August 1865.

Mathematical Physics

In his first session Hirst lectured three times per week to both Junior and Senior Classes. The subjects treated in the former class were:- Elementary Statics and Dynamics; elements of Plane Astronomy; Newton's Principia, sections 1 to 3; Elementary Hydrostatics and Hydrodynamics; fundamental laws of Sound, Light, Heat, Magnetism and Electricity and the theory of the principal instruments employed in these sciences. The senior class covered the higher branches of Statics; Kinematics; Dynamics of particles and rigid bodies; elements of the calculus of attraction and its applications in Astronomy, Magnetism and Electricity; theory of Wave Motion and its applications to the phenomena of Sound, Light and Heat.

In the 1866-7 Session his courses were divided into three parts terminating at or about Christmas, Easter, and Midsummer. The fee for each part of a course was £2 12s 6d; for a whole course, £7 7s; Perpetual, £10 10s. The Junior Class met on Mondays, Wednesdays, and Fridays, from 9 to 10 am, the Senior Class following from 4 to 5 pm on the same days. The subjects treated were:-

Junior Class

I Elementary Statics, Hydrostatics, and Kinematics.
II Elementary Dynamics and Optics.
III The Elements of Plane Astronomy, and of the Theories of
Sound, Light, and Heat.

Senior Class

I Higher branches of Statics and Kinematics.
II Dynamics of particles and of rigid bodies.
III Hydrostatics and Hydrodynamics.

An extra class on the Mathematical Treatment of the Theories of Sound, Light, Heat, and Electricity was available if required.

In 1867 Hirst succeeded De Morgan in the Chair of Pure Mathematics and, under the title of Professor of Pure and Applied Mathematics, continued with the teaching of the higher branches of mathematical physics. This arrangement only lasted one session, since he soon found the combined work too onerous. T. B. Moore was appointed Professor of Applied Mathematics and Mechanics, being assigned the duty of providing the courses in Mechanics, Hydrostatics, and Astronomy required by candidates for the B.Sc. and B.A. degrees of the University of London, and also that of giving the instruction in Applied Mechanics for students of Engineering, while Hirst devoted himself to Pure Mathematics. However he soon found the work of his professorship so demanding as to leave no time for research and even beyond his physical capacity. He resigned in 1870 to become Assistant Register of the University, and from 1873 to 1883 he was Director of Naval Studies at the Royal Naval College, Greenwich. (B.321-2).

Experimental Physics

Carey Foster started work immediately and on 8 August 1865 the Management Committee agreed that he should either have the services of a Beadle for three days per week or £26 per annum towards the salary of an assistant; moreover he wrote on 30 August requesting the expenditure of £63 on apparatus required at once. In his first session he lectured on Monday, Wednesday and Friday from 4 to 5 p.m. There were two divisions in his course, the first ending near Christmas included the physical subjects required for the Matriculation Examination of the University of London, namely, Dynamics or the study of Mechanical Forces; Descriptive Optics; Acoustics: the second included Theoretical Optics; Heat; Magnetism; Electricity.

Physical Laboratory

The teaching of experimental physics obviously required a laboratory so on 19 June 1866 his proposal for the establishment of a physical laboratory and courses of practical instruction in physics came before the Management Committee, which resolved that he be invited to attend its next meeting to submit full details and explanations. This he did on 3 July 1866 and, after inspecting the theatre and room occupied by the professor, the Committee resolved that "the Council be recommended to allow the plan suggested by Professor Foster to be tried; that space be provided for the Physical Laboratory by such alteration in the arrangement of the apparatus room and the theatre of Natural Philosophy as Professor Foster may think desirable; that £1 per week be allowed for payment of Professor Foster's assistant and that all the additional annual expenses of the Physical Laboratory are to be made a first charge on the fees paid by the students attending it; that the necessary tools and other apparatus to be used in the laboratory be provided at the expense of the College, the sum to be expended not to exceed £30." At its meeting on 7 July the Council adopted the recommendation subject to Professor Foster's careful examination of the "stability of the room where the experiments are to be performed." On 31 July Carey Foster was given leave to engage William Grant as his assistant from 30 August next.

In his account of the Physics Department (K.64-70) Carey Foster describes how the upper platform above the seats in the lecture theatre was cleared of most of the miscellaneous collection of models of inventions, which had been presented to the College by the Society of Arts, and were mostly in a very decrepit condition, thereby making room for most of the apparatus-cases from the apparatus-room, which thus became free for experimental work. He states that "This room was accordingly opened at the beginning of the session 1867-68 as a 'Physical Laboratory' and it is believed that this was the earliest attempt in England to provide practical instruction for students of Physics, though Professor W. Thomson (Lord Kelvin) had established a Physical Laboratory in the University of Glasgow, a good many years before." Why he gave the wrong sessional date is a mystery, since the 1866-67 Calendar and Fee Book clearly establish that the laboratory course started in 1866 and not in 1867. Early in the latter year the laboratory was extended by the reacquisition of the other room adjacent to the theatre, originally allocated to Natural Philosophy but then occupied by the School; then two more rooms were added on the floor above, one being used by Grant as a workshop for making and repairing apparatus; and the Still Room in the basement underneath the Council Room and looking out on to the school playground was also acquired. This room, later known as the "dungeon", was the only room with a really substantial floor and was reserved for the professor and students engaged in research. Finally two rooms on the top floor of the South Wing, which were not needed for the purposes of the School, were made into one and assigned to the department.

The Courses

The Calendar for the 1866-7 Session announced Carey Foster's courses as follows:-

A - THEORETICAL COURSES

I General Course
Monday, Wednesday, Friday, from 4 to 5, until the end of April; from that time to the end of the Session, at some convenient hour.
The Course is divided into Two Divisions: namely, from the beginning of the Session to Christmas, and from Christmas to the end of the Session. Students can enter for the whole Course, or for either Division separately.
Fee, £7 7s. For the First Division, £3 13s 6d; for the Second Division, £4 4s; for perpetual admission to the Class, £10 10s. The subjects of the Course will be treated in the following order:-

First Division
I Mechanics: including the Laws of Equilibrium and Motion of Solid Bodies, Hydrostatics, and Hydrodynamics, Pneumatics.
II Acoustics. Production, Propagation, and General Properties of Sound.
III Optics. General Properties of Light - Laws of Reflexion, and Simple Refraction, with the principal phenomena depending upon them.
N.B. A knowledge of the elements of the above subjects is required for the Matriculation Examination of the University of London.

Second Division
IV Theoretical Optics. Illustrations of the Undulatory Theory of Light, by the phenomena of Interference, Diffraction, Polarization, and Double Refraction.
V Heat. (1) Radiant Heat; its general properties, and its relation to Light.
(2) Effects of Heat on Material Bodies, and its relation to other forms of Energy.
VI Magnetism. Phenomena presented by Magnets and Magnetic Substances; Measurement of Magnetic Forces; Terrestrial Magnetism.
VII Electricity. (1) Sources and Effects of Accumulated Electricity. (2) Sources and Effects of Electric Currents.

As a single Session does not afford time for a full treatment of all the above Branches of Physics, those included in the Second Division of the Course are divided into Principal Subjects, which are treated with as much detail as practicable, and Subsidiary Subjects, of which only the most fundamental parts are considered; and those branches which are taken as Principal subjects in one Session, are taken as Secondary subjects in the next Session, and vice versa.
The Principal Subjects for the Second Division of the present Session, 1866-67, will be Magnetism and Electricity.

II Elementary Summer Course
This course will consist of about thirty lectures, beginning on or about the 1st of April, and terminating at the end of the Session. The Days and Hour of Lecture will be announced shortly before the beginning of the Course; Fee, £3 13s 6d.
Subjects: The Elements of Mechanics, Hydrostatics, Pneumatics, Acoustics, and Optics.
N.B. A knowledge of the above subjects is required for the Matriculation Examination of the University of London.

B - PRACTICAL COURSES

I Physical Laboratory
For Practical Instruction in Experimental Physics.
The Physical Laboratory will be open to Students daily throughout the Session from 10am to 5pm, except on Saturdays, when it will be closed at 1pm.
The object of this Course is to afford instruction (1) in Pure Physics, and (2) in the practical Applications of Physical Science.
The general course of instruction, which however may be modified in the case of individual students, according to their previous attainments or special objects, is as follows:- Students are first taught the construction and use of the most important physical apparatus (as for example the Air Pump, Electrical machine, Galvanic battery), and are made practically familiar with the conditions needed for the production of the fundamental phenomena of the various branches of physics; they are then taught the use of the most important measuring instruments (as for example, the Balance, Barometer, Theodolite, Galvanometer), and are practised in making accurate observations by means of them. Students who may have completed this preparatory course, will be set to repeat and verify some standard physical research, or will be encouraged to undertake an original investigation.

The instruction in the Physical Laboratory being for the most part individual, Students can enter at any period for the Session.
Fees for the Session:- six days per week, £21; four days per week, £17 17s; three days per week, £13 13s; two days per week, £9 9s; one day per week, £5 5s.
Fees for shorter periods, six days per week:- six months, £17 17s; five months, £15 15s; four months, £13 13s; three months, £10 10s; two months, £7 7s; one month, £4 4s.
Students entered for one, two, or three days per week, may, with the consent of the Professor, distribute their time of working over a greater number of days; thus a student entered for one day per week, may work three hours a day for two days, or two hours a day for three days per week.
The above payments entitle Students to the use the apparatus belonging to the Physical Cabinet of the College, under such regulations as the Professor may prescribe; but in case of any apparatus receiving an injury, which, in the judgment of the Professor, amounts to more than legitimate wear and tear, the Student in whose charge the apparatus is at the time must make good the injury, or, if required, replace the apparatus at his own expense.

II Mechanical Workshop
Monday, Wednesday, Thursday, and Friday from 10am to 5pm; Saturday, 10 to 1.
Fees, the same as for the Physical Laboratory (see above).
Practical instruction in Joinery, Turning, and the working of Wood and Metals is given by Mr. William Grant, Assistant to the Professor of Experimental Physics, under the superintendence of the Professor. In addition to the Fee paid to the College, Students are required to pay for most of their materials, and for some of their tools.

18 students enrolled in 1866 for this first physical laboratory course in England. Among them was C. Wheatstone, the son of Sir Charles Wheatstone F.R.S. of King's College London fame, and five Japanese students (of assumed names) who came to study in England in 1864 and 1865 from Satsuma. (W.21-2). Apparently J. Ambrose Fleming was a student of the Experimental Physics course but not of this laboratory course.

Credit for the establishment of the first physics laboratory for undergraduates in England is almost invariably attributed to either R. B. Clifton at Oxford (e.g. see Alexander Wood, The Cavendish Laboratory, 1946, C.U.P., 7) or W. Grylls Adams at King's College London (Cajori, A History of Physics, 1929, The Macmillan Co., New York, 387 et seq.). A. Wood states that Clifton borrowed a room and started practical work in 1867; the building of the Clarendon Laboratory was begun in 1868, it was in partial use in 1870 and completed in 1872. Rucker, in his presidential address to Section A of the British Association at Oxford on 8 August 1894, referred to the Clarendon Laboratory, in which the meetings of Section A were to be held, as follows:- "... the first laboratory in this country which was specially built and designed for the study of experimental physics. It has served as a type. Clerk Maxwell visited it while planning the Cavendish Laboratory, and traces of Prof. Clifton's design can be detected in several of our university colleges."(Nature 50, 1894, 344). Cajori refers to a letter in Nature (3, 1871, 323) in which Adams states ..."I believe that Clifton was the first to propose, more than three years ago, that a course of training in a physical laboratory should form part of the regular work of every student of physics. This system was adopted and at once put into action at King's College... and has been working now for nearly three years." There then follows an account of the arrangements made for the practical work at King's. Clerk Maxwell, the first Professor of Experimental Physics at Cambridge, was appointed in 1871; the building of the Cavendish Laboratory was started in 1872, and, on 25 June 1874, nine days after its opening, a detailed description of the new laboratory was published in Nature. It began with the observation that "The genius for research possessed by Professor Clerk Maxwell and the fact that it is open to all students of the University of Cambridge for researches, will, if we mistake not, make this before long a building very noteworthy in English science." In Scotland William Thomson (Lord Kelvin) set up a research laboratory in the old wine cellar at Glasgow University in or about 1846, and this seems to have developed into a teaching laboratory. The University Calendar for the 1863-4 session states that "the laboratory in connection with the (natural philosophy) class is open daily from 9am to 4pm for experimental exercises and investigations under the direction of the Professor and his official assistant."(A. Gray, Lord Kelvin, 1908, Dent). 1846 was Thomson's first year in his chair; he was only 23 and had spent some ten weeks in the previous year assisting Regnault, e.g., stirring the water in his calorimeters. A. Wood further records that before compiling the list of apparatus he would require for his laboratory, Maxwell visited Thomson's laboratory at Glasgow and Clifton's at Oxford.

Cajori records that German Professors of Physics allowed their best students to work in their private laboratories, usually in their own houses. Thus Magnus did so at Berlin round about 1846 and his private laboratory apparently evolved into the physical laboratory of the University of Berlin, which was opened in 1863. In a review of Kohlrausch's 'Leitfaden de Praktischen Physics', published in 1870, Akin refers to the description of experiments performed by students at Gottingen for several years past. He explains the rarity of physical, as compared with chemical, laboratories as follows:-"Chemical operations proper possess, it is true, a considerable degree of uniformity and are capable of methodical treatment and exposition; but physical processes and manipulations are multiform, numerous and difficult to classify. That is the reason why physical laboratories are, as yet, few and far between and none of them so systematically organised as the chemical laboratories; and why the workers in Chemistry outdo in individual productiveness the workers of Physics." (Nature 3, 1871, 121). In the same volume of Nature (241) Professor E. C. Picketing gives an account of the arrangements of practical work at the Massachusetts Institute of Technology, and states that at least four similar laboratories were in operation or preparation in America. Tyndall working under Gerling at Marburg (1848-50), wrote that he was doing experiments on electricity and magnetism, but it is not clear that any systematic course of training was given. Adams in his account of 'The Foundation of the Physical Laboratory for Students at King's College, London' (King's College Archives) refers to a visit to Paris in the Easter vacation of 1868 in search of laboratories for the practical teaching of students in physics; at the Sorbonne he found a very complete laboratory, established by M. Jamin, where students were already engaged in the determination of physical constants, but there was no such laboratory anywhere else in France. He also reports finding no physical laboratory for students in Germany!

Although Adams does not claim any priority in his Nature letter, it is surprising that he makes no reference to Carey Foster's student laboratory, since he obviously knew the man, and Charles Wheatstone, a son of his famous predecessor in the chair at King's College, was actually working in the laboratory. For some unknown reason Carey Foster didn't bother to write to Nature claiming priority; it may be that being familiar with practical work in chemistry, knowing of the laboratories in Germany and of Thomson's laboratory in Glasgow, he considered the matter of little consequence. Porter, however, made the position crystal clear, writing as follows:- "Carey Foster at once set to work to make his department correspond to its new title. Up to that time there had been no systematic teaching of the experimental side of physics in the country. Graduates had indeed visited various laboratories to extend their experience and taken part in the private researches of their professors; but that is a totally different thing from systematic practical tuition side by side with instruction in theory which is characteristic of a modern laboratory. The programme for the session 1866-67 provided for such tuition and thus Carey Foster became the pioneer in this direction. Since this fact has been the subject of controversy the practical syllabus for that Session is hereto appended..." (P.5-6 & B.312).

Orson Wood carefully researched the introduction of systematic teaching of practical physics to undergraduates, his findings being recorded in his typescript (W.24-27) and incorporated above. As recently as 1980, Profs. Wilkinson and Domb of King's College restated the claim of priority for Adams in their article, 'Physics at King's', but the author quickly rebutted it.(Phys.Bull. 31, 1980, 18-19 & 130).

Carey Foster played a prominent role in bringing about the admission of women students to the College on the same basis as men. It will be recalled (see p.4) that the earliest attendance of any ladies at a course of lectures in College was in May 1832 when Mrs. J. P. Potter and Miss Rogers joined Ritchie's juvenile course of six lectures on electricity and thus became the first two female university students in the country. Nearly thirty years later John Marshall F.R.S., a surgeon at U.C.H. and later Professor of Surgery, delivered a course of thirteen lectures on Animal Physiology in the 1861-2 session to a class of 113 women. In the 1867-8 session it was decided that a series of Tuesday Evening Lectures should be given upon the subjects of Art, Science and Literature, adapted to a general audience, including ladies. This led to the founding in the following session of the London Ladies' Educational Association which proceeded to organise courses of lectures for ladies over the age of seventeen similar to those on offer to men at the College.

The first lectures began in February 1869 and were given in the Beethoven Rooms at 27 Harley Street. There were two courses, each of 23 lectures, one by Henry Morley on The Spirit of English Literature and the other by Carey Foster on Acoustics. Although the notice given was relatively short, 103 tickets at 2 guineas each were sold for Morley's course and 58 for Carey Foster's. When apparatus was required for demonstrations Grant had to transport it to and from Harley Street twice a week. Consequently the lectures in Physics and those in Chemistry by Professor Williamson were transferred to the College. Five courses of lectures were delivered during the Michaelmas and Lent terms of the 1869-70 session, those on Latin, English and French Literatures being in St. George's Hall and those on Physics and Chemistry in the Lecture Rooms at College where there were separate entrances for the ladies classes. The lectures were advertised in Nature (Vol.1,Nov.11,65,1869), Carey Foster's course of 36 lectures on Dynamics and Heat at 11.45 a.m. on Wednesdays and 1 p.m. on Saturdays starting on Wednesday 10 November. Grant recalls "With regard to the admission of women to the classes in University College great caution was exercised and they were not allowed at first to enter by the Main gate of the College. The Physics Department however could be reached without the necessity of entering by the Main Gate and so it was chosen as the first Department into which women were to be admitted. That Department could be reached through the School Playground (now the South Quadrangle) and up the back stairs and that was the way women had to come and go to the Physics classes at first."(G.23). Hirst also gave a course on Elementary Geometry beginning on 24 January 1870. In the 1871-2 session the Council consented to admit all of the women's classes and the number rose to twenty-one. However the classes met and separated at the half-hours, when the men were safely occupied at their own lectures, and the women were admitted by a side door to avoid crossing the front quadrangle. On 28 March 1874 the Council approved Carey Foster's application to admit ladies to study in the Physical Laboratory on the same terms and under the same conditions as the men subject to the provision of a separate room for the ladies and no additional expenditure.

The Calendars from the 1874-5 to the 1877-8 sessions announced in the Physical Laboratory sections that "By special permission of the Council Ladies are admitted to work in the Laboratory under the same conditions in all respects as other students." In 1878 women were admitted to all Faculties except Medicine, there being 309 of them with 600 men, and the University admitted women to degrees. The 1878-9 Calendar included the Junior Class for Women; A Elementary Mechanics; B Experimental Physics, identical to the men's course, but held at different times. However on 3 May 1879 learning that Carey Foster would not be able to take his classes for some weeks owing to illness, the Council recommended that the women's and men's classes should be combined during Carey Foster's illness provided that there was no objection by the students; there was none so the Council endorsed the recommendation. Although classes were mixed, even in 1884 women were not permitted to enter the physics lecture-room by the ordinary door, but were conducted by Grant to the little entrance door high up at the back and told to sit in the topmost row, thus leaving a gulf of empty rows between them and the backs of the men down below. Grant writes "The Laboratory as well as the lectures was open to women and about six or seven entered it as students. Three of these were sisters named Martineau and the youngest afterwards became Principal of Morley College in Waterloo Road and held that office until she died. Women have continued to work in the Laboratory since then but the only one taken special notice of in its early days was Miss Watson. On one occasion when she passed an examination very successfully she told me when preparing for it that she was working 18 hours a day. In these circumstances one would have expected her to pass not only with honours but with flying colours. She afterwards went to South Africa and died there but her name is commemorated by the Ellen Watson Scholarship."(G.23-4). This is the Ellen Watson Memorial Scholarship in Applied Mathematics founded in 1882 by the subscribers to a fund raised in her memory. (An account of this development is given in Bellot (367-73), there being a more detailed treatment in the revised text of N.B.Harte's Centenary Lecture, 'The Admission of Women to University College London', delivered on 21 November 1978.)

Carey Foster managed without academic assistance until the 1873-4 session. Bellot recalls that an assistant was the private servant of the professor, appointed by him subject to Council approval and paid out of his share of the fees. The number of hours of class teaching in physics increased from 180 in the 1868-9 session to 400 in the 1879-80 session apart from the laboratory which was open for 35 hours a week. In and after the 1873-4 session Carey Foster had one, sometimes two, and on occasions, three assistants. Consequently his average income for the period 1865 to 1879 was not quite £276 and it never reached £400. (B.376). After a Senate committee on the conduct of the mathematical and physical classes, the Council awarded him £100 per session from the General Fund in 1881 in recognition of his reorganization of the Chair of Physics and the formation of the Laboratory for Practical Physics. Becoming the first Quain Professor of Physics in the 1888-9 session, his position improved in 1890 when the Trustees of the Quain Fund assigned the annual sum of £500 to promote the study of physics; £300 was added to his salary, £100 for the payment of a skilled assistant, i.e. Grant, and £100 for a laboratory fund at the professor's disposal. Carey Foster also refers to another assistant in the laboratory. (K.69).

His first academic assistant was Benjamin Loewy F.R.A.S., who had been conducting evening classes since October 1870. A regular series of evening classes had been held since 1866, replacing in some measure the schoolmasters' classes which had ceased in 1864. In the 1870-1 session Loewy had given two courses of 20 lectures for students preparing for the Matriculation Examination, and in the following session had also given a two-hourly course on Wednesdays during the Lent and Summer terms supplementing Carey Foster's regular course of physics as far as was required by students taking the 1st. B.Sc. and Preliminary M.B. examinations. He was engaged in 1873 to take the exercise classes then introduced for first and second-year students. Oliver Lodge, then a third-year student, replaced him in 1874. From 1875-8 Lodge was a demonstrator, a part-time post, since in 1875 he was appointed Reader in Natural Philosophy at Bedford College in York Place. During the 1878-9 session he not only assisted Carey Foster but deputised for the Professor of Applied Mathematics, W.K.Clifford, who was ill and died in 1879. Finally he was Assistant Professor from 1879 to 1881 when he became Professor of Physics at Liverpool University College. He published 15 papers, and numerous letters in Nature on a wide range of topics while at College. Among his papers were two, jointly with Carey Foster, 'On the flow of Electricity in a Plane Conducting Surface' (Proc.Phys.Soc.1876,1,113;119). Lodge was the first President of the College Chemical and Physical Society in 1876-7, and he returned to College fifty years later to deliver one of the Addresses given in celebration of the Centenary of its Foundation.

In October 1881 John Buchanan succeeded Lodge as Demonstrator, being assigned the lectures to the Lower Junior (Matriculation) Class, and to help in the Exercise and Practical Classes, and in the Physical Laboratory. He remained alone until October 1884 when he was joined by another demonstrator, R.H.Fison. Buchanan left in 1886, leaving Fison as the only demonstrator for the ensuing session; however he was appointed Assistant Professor in 1887 and joined by two demonstrators in 1888, namely H.L.Reed and J.J.Stewart. Reed only stayed for one session, being replaced by J.Rose-Innes. Stewart stayed for two sessions and was not replaced for a session and then in October 1891 by A.W.Porter, who had graduated with first-class honours in the Summer. Rose-Innes left in 1893 and Fison went in 1894 to take charge of the 1st. M.B. classes at Guy's Hospital Medical School. Porter was joined by C.V.Burton and N.Eumorfopoulos as demonstrators in 1894, Burton left in 1896 when Porter was made Assistant Professor, he and Eumorfopoulos remaining as Carey Foster's academic assistants until his retirement in 1898.

According to Porter, Fison "was an excellent leader and disciplinarian; his ready wit quelled at once any attempts at effervescence on the part of his classes. His lucidity and exceedingly neat blackboard work were great assets with him. He was not distinguished as an investigator. He published a paper jointly with Carey Foster on the difference of potential required to give sparks in air (in connection with which his name is often misquoted as Pryson owing to an unfortunate printer's error); and a second paper on a method of comparing unequal capacities." (P.11). Fison must have been closely connected with Carey Foster since he was chosen to write his obituary notice. In June 1886 when at King's College Cambridge Rose-Innes donated the interest, c.£60 per annum, on a certain sum at his disposal for a fund under the Professor's control to purchase apparatus required for special research or teaching in physics, and from time to time he presented pieces of apparatus to the department, and he was elected to the Fellowship of the College in 1890. He worked on the reduction of gas-thermometric temperatures to the thermodynamic scale, and in 1909 equipped the laboratory with the porous-plug apparatus used by Eumorfopoulos and his collaborators.

Development of Lecture Courses

In the 1871-2 session Carey Foster replaced the separate Junior and Senior courses by a single course of five lectures per week. Students were advised to write out abstracts of the lectures, either from memory or short notes, as soon as possible after they had been delivered, and to show them to the Professor, who would correct mistakes and explain doubtful points from 11 to 12 on Tuesday and Thursday mornings. However this five-lecture course was replaced in the next session by separate first and second-year courses, each having three lectures per week and covering half of the former topics.

Junior and Senior Classes were reintroduced in the 1876-7 session, three lectures and two exercise classes per week being associated with each course. The same general order of subjects was followed in each class but there was more mathematical treatment of certain topics in the senior class and "especially a discussion of methods employed and results obtained in investigating the quantitative relations of physical phenomena." For the first time students were advised which classes were recommended for the various university examinations. In the following session an Elementary Mechanics course was introduced as Division A of the Junior Class, two lectures and two exercise classes being assigned to it; also Molecular Physics - Elasticity, Capillarity - was introduced as an additional subject in the Senior Class. A Lower Junior Class was held for the first time in the 1879-80 session, it being an introduction to the more detailed and systematic study of the Junior Class for students insufficiently acquainted with mathematics. After 1881 the number of courses began to increase and vary, e.g., for one session only in 1883 there was introduced Principles of Electrical Engineering and Electrical Measurement referring as far as possible to work done in the Physical and Electrical Laboratories.

It should be noted that in the 1884-5 session at the suggestion of Carey Foster his old student, Dr. J.A.Fleming, was invited to give a course of lectures on Electro-Technology, and in the following year there was established the Chair of Electrical Technology, to which Fleming was appointed, thereby becoming the first Professor of Electrical Engineering in Britain. (B.391).

In the 1887-8 session Carey Foster repeated 15 easy experimental lectures on Properties of Matter and Elements of Heat, Magnetism and Electricity, subjects termed Chemical Physics in the Regulations for the First Examination of the Conjoint Board. Fison gave this course twice in the 1893-4 session for the last time, it being replaced by a special course of Chemistry and Chemical Physics given by Professor (later Sir William) Ramsay. For the last three sessions the Chemical Physics course was not listed under Physics but under the Faculty of Medicine courses. In the 1890-1 session the list of courses and lecturers was as follows:-

A Lower Junior (Matriculation) Class Rose-Innes
B Elementary Mechanics Fison
C Experimental Physics Carey Foster
D Supplementary Course on Heat Fison
E Senior Class Carey Foster & Rose-Innes
F Elementary Course on Physical Measurement
G Elementary Course on Electrical Measurement
H Physical Laboratory

G was introduced in this session specially for students wishing to enter the Class of Electrical Technology and to qualify as Electrical Engineers; instruction was given in the use of the most important electrical measuring instruments, and in accuracy of measurement of electrical and magnetic quantities. D was given for the last time in this session, and as explained earlier F was given for the last time in the 1891-2 session, it being replaced by the addition of 1.5 hr. of practical work to C in the following session. With the departure of Rose-Innes in 1893 A disappeared leaving B, C, E, G and H in the 1893-4 session, labelled A, B, C, D and E respectively in the hands of Carey Foster, Fison and Grant. The next session saw the addition of a Mechanics (Matriculation) Class taken by Burton; the appearance of two Experimental Physics Courses, one in the first term for Engineers taken by Porter and the other for Intermediate Science and Preliminary Science (Medical Examination) students taken by Carey Foster; and the Senior Class being listed as Physics for B.Sc. examination and Engineers, still given by Carey Foster. In the last three sessions of Carey Foster's reign the courses were as follows:-

A Introductory Mechanics and Hydrostatics
B Elementary Mechanics
C Experimental Physics
D Senior Physics
E Electrical Measurements
F Physical Laboratory

Burton gave A in his last (1895-6) session and was then replaced by Eumorfopoulos, Porter and Carey Foster giving B and E, and C and D respectively.

New Accommodation

In the Summer of 1887 the College spent £225 equipping the dungeon with additional apparatus for instruction in physics and electrical technology; this included an Otto gas-engine, a dynamo-machine, 30 accumulators, an electric-arc lamp, a photometer and the necessary measuring instruments etc. Fleming had charge of the room, Carey Foster having provided £100 of the cost from his apparatus fund. However the accommodation available for the department was quite inadequate. Porter testifies to the difficulties in 1890 under which research laboured - "his research apparatus was completely dismounted each week in order to make room for the undergraduate worker and had to be built up again each following week."(P.8).

Carey Foster continually strove for a purpose-built laboratory and in July 1888 an appeal was made to friends of the College for funds to build a Physics Laboratory and to make further provision for the Department of Electrical Technology, it being estimated that c.£6000 would be required, £1000 having been subscribed or promised. The response was unsatisfactory, but the College decided to go ahead by incurring further debt if necessary. In 1891 a public appeal was made for an Extension Fund of £50,000, the urgent needs of the College being stated as "1. A new Laboratory for Experimental Physics: 2. A properly equipped Electrical Laboratory: 3. Further accommodation and additional machines in the Engineering School: 4. A collection of architectural models and a School of Architectural Drawing: 5. Additional Laboratory space and apparatus for the work it is contemplated to undertake in connection with the Society for the Extension of University Teaching in London." (B.378-9).

The new laboratory (see H & N 128;84), named after Carey Foster in 1899, was built in the south quadrangle between the Central (Library) Wing and the Botanical Theatre and was occupied for the first time at the beginning of the 1892-3 session. The extension of the South Wing, devoted to new Mechanical and Electrical Laboratories, was opened in May 1893 by the Duke of Connaught. When the Department of Mechanical Engineering moved into the new extension fronting upon Gower Street, the basement and ground floor of the Central Wing were assigned to the Physics Department. After a complete internal reconstruction costing £3000, the rooms were ready for use early in the 1893-4 session. The classes of Physics were accordingly transferred from the rooms which had been occupied since the foundation of the College to the new rooms in the Central Wing, the Department of Mathematics which had vacated its rooms on the aforementioned ground floor moving into the old rooms relinquished by the Physics Department. Thus the accommodation of the department was probably as complete and well adapted for its purpose as was to be found anywhere in the kingdom, a fitting reward for the persistent efforts of Carey Foster. (K.68).

Carey Foster's Retirement

On 4 November 1897 the Council received Carey Foster's letter announcing his intention to resign his chair at the end of the session in June 1898 then having completed 33 years as Professor in the College, this being for the good of the College and the furtherance of science, and to make way for a younger man with fresher ideas. A unanimous resolution was passed "that in accepting the resignation of Professor Carey Foster, the Council desire to record their high appreciation of the services he has rendered to the College during the long period of 32 years, and of the distinction which his eminent scientific position has conferred on the College. They desire also to express their hope that the termination of his professorial work will not sever his active connexion with the College, and that they may still have the advantage of his assistance as a member of Council." In 1900 he accepted the invitation to become the first Principal of the College and he served in that office until 1904, when he was succeeded by Gregory Foster, then Secretary of the College. As Principal he represented the College on the Senate of the University under its new 1898 constitution, and played a prominent part in the resulting reorganization, and the negotiations that led up to the incorporation of the College in the University on 1 January 1907.

To appreciate this new constitution, it should be emphasised that what had hitherto been the university became University College London when the seal was affixed to the College charter on 28 November 1836. Immediately afterwards, on the same day was sealed the charter of the new University of London. This second charter "established a body to be known as the University of London, empowered to grant degrees in Arts, Laws, and Medicine, after examination, to candidates holding certificates of having completed a course of instruction at University College, King's College, and such other institutions as might hereafter be approved for the purpose." (B.248). In 1858 the examinations of the university were thrown open to all, irrespective of the manner or place of their education, and consequently without the requirement of any certificate of preparation; however this new charter included the important provision for the granting of degrees in science. The university remained an examining body until the University of London Act of 1898 transformed it into a federal university, the various colleges becoming schools of the university and their students, internal students in the London area, as distinct from the external students studying elsewhere. Faculties and Boards of Studies were established, the latter advising on matters relating to courses of study, provision for teaching or research, examinations and the appointment of examiners, or the granting of degrees. "The Board of Studies in Physics met for the first time on January 28, 1901 when Professor Callendar, Carey Foster's successor in the Quain Chair was elected Chairman. The first Internal B.Sc. Honours examination in Physics was held in 1903, only two candidates were successful, a Miss East from Royal Holloway College and Mr. W. Tannak from the Royal College of Science - each obtaining only third class honours." (W.29). "The establishment of the 'internal side' of the university, which was in full working order in the session 1902-3, freed the teaching from the necessity of conforming to examination schedules made by a Senate which had no Boards of Study to advise it, and enabled the student to study the subject instead of studying his examiner. The provision that graduates of other universities might be admitted as Internal Students to work for higher degrees of the university stimulated post-graduate and research work..." (B.401). The College had proposed in 1898 to vest its site, land, buildings and endowments in the reconstituted university, and an appeal was launched in 1902 to fund this "incorporation", inaugurated by the Drapers' Company agreeing to pay off the College's accumulated deficit of £30,000. The University College, London (Transfer) Act of 1905 came into operation on 1 January 1907; however it was necessary for University College School and the Medical School to be constituted as separate bodies. The Council became the College Committee and the Professorial Board replaced the College Senate. The professors, who had become "recognised teachers" of the university in 1900, now became "appointed teachers" occupying chairs of the university.

Old Students

Carey Foster concluded his account of the department in Ker's Notes and Materials (69-70) with the following list of his old students who had distinguished themselves in various ways:-

W. E. Ayrton, F.R.S., Professor in the Central Institute of Technology.
Oliver J. Lodge, F.R.S., Professor in University College, Liverpool.
Ellen Watson (the late).
H. Forster Morley, M.A., D.Sc., Fellow of the College.
Theodore Beck, Principal, Aligarh College.
Lewis H. Edmunds, D.Sc., Q.C., Fellow of the College.
J. V. Jones, F.R.S., Principal, University College of South Wales and Monmouthshire; Fellow of the College.
M. J. Jackson, D.Sc., Principal, Sind College, Kurachi; Fellow of the College.
W. E. Sumpner, D.Sc., Fellow of the College.
H. C. Draper, D.Sc., Headmaster, Rutlish Science Schools.
John Buchanan, M.A., Gordon's College, Aberdeen.
A. P. Chattock, Professor in University College, Bristol.
G. W. de Tunzelmann, B.Sc., Principal of the Electrical and Engineering College, Penywern Road.
Hugh E. Harrison, B.Sc., Principal of the Electrical Training College, Faraday House.
S. Z. de Ferranti, Electrical Engineer.
J. A. Fleming, F.R.S., Professor in and Fellow of the College.
T. H. Beare, B.Sc., Professor in the College.
G. U. Yule, Assistant Professor in the College.
A. W. Porter, Assistant Professor in and Fellow of the College.
N. Eumorfopoulos, B.Sc., Demonstrator in the College.
D. K. Morris, Ph.D., Fellow of the College.
J. T. Morris, Demonstrator, Electrical Laboratory, University College.
F. Womack, B.Sc., Professor in Bedford College, London.
J. Rose-Innes, M.A., B.Sc., Fellow of the College.
W. Sutherland, M.A., Melbourne.
A. H. Fison, D.Sc., late Assistant Professor in the College.
C. V. Burton, D.Sc., late Demonstrator in the College.
J. Sakurai, Professor in the Imperial College of Science, University of Tokyo.
W. C. D. Whetham, M.A., Fellow of Trinity College, Cambridge.

Carey Foster Obituary

Fison introduces his obituary notice of George Carey Foster (Trans.Chem.Soc.Vol.115, 1,412-27, 1919) in these words "In the death of Professor Carey Foster in his eighty-fourth year on February 9th, there are many who will feel the loss of a kind and generous friend, to whose gentle sympathy and encouragement much of the happiness, as well as much of the success, of their own lives has been due. A man of extreme modesty and of high if not commanding ability, Carey Foster had made few direct contributions to scientific literature; but the soundness of his judgment, his almost passionate love of exact knowledge, and his enthusiasm, earned the respect of all, and made his presence invaluable on the many committees of learned societies, the British Association, and the various university boards of which he became a member. An extreme diffidence and a nervous shyness that was not without a peculiar charm to those who came to know him well, as well as a hesitation to express a definite opinion on subjects on which he did not feel on the firmest ground, made it easy to undervalue the services he rendered to science and education during the course of a long and active life."

He was born in 1835 at Sabden in Lancashire, the only son of George Foster, a calico printer and a J.P. for Lancashire and the West Riding of Yorkshire. After an early education in private schools, he became a student of the College at the age of eighteen and in his twentieth year graduated B.A. with Honours and a prize in Chemistry. For the next three years he was assistant to Professor Alexander Williamson in the Department of Chemistry. Then in 1858 he went to the continent to study under Kekule at Ghent, Jamin at Paris and Quincke at Heidelburg. During this period while he continued with his chemical studies, his interest became more and more directed to physics which was then assuming increasing importance through the work of Clausius, Helmholtz, Kelvin and Maxwell. In 1862 he accepted an invitation to the Chair of Natural Philosophy at the Andersonian University, Glasgow. While there he wrote two articles on Heat for the first edition of Watts's Dictionary of Chemistry in 1863. These articles occupying over 150 pages of closely printed text were a remarkable critical review of this important branch of physics, and immediately established his reputation as a clear thinker and able exponent of Physics. In 1865, encouraged by his friend and former teacher, Williamson, he became the successful candidate for the Chair of Experimental Physics at the College.

Carey Foster's contributions to chemistry were published between 1857 and 1867. The most important were three papers published jointly with Matthiessen in 1861, 1863 and 1867 on the chemistry of narcotine and its products of decomposition, papers making "a long step forward in the knowledge of the constitution of the alkaloids, and may, indeed, be termed classical. The accuracy of the work has been amply confirmed by subsequent investigation."(op. cit. 416). However his judgment on some chemical topics was questionable. Apparently in the discussion which followed Newland's account of his "Law of Octaves" given to the Chemical Society in 1863, he remarked "Has the author tried arranging the elements in alphabetical order?"! (W.35). Elected a Fellow of the Chemical Society in 1856, he served as a Council member from 1865-8, 1872-5 and 1885-6, and as Vice-President from 1888-90.

He is credited with 21 papers in the Royal Society Catalogue, 9 being concerned with chemistry. His best known paper in physics, 'On a Modified Form of Wheatstone's Bridge, and Methods of measuring Small Resistances', was read before a meeting of the Society of Telegraph Engineers (now the Institution of Electrical Engineers) in 1872 .(Telegraph Engineers' Journal, 1872-1873, 1, 196). A Carey Foster bridge designed and constructed in the departmental workshop in 1946 was exhibited at the Sesquicentenary Commemoration; this bridge was then used in the undergraduate laboratory to determine the resistivity of copper in the form of a wire having a resistance of c. 0.01ohm, and to measure the change of resistance of a wire on deformation by a tensile stress; and it still continues its important teaching role in the physics undergraduate laboratory. In 1881 he published 'An account of Preliminary Experiments for the Determination of the Electromagnetic Unit of Resistance in Absolute Measure' (Rep.Brit.Assoc.,1881); however the results were not sufficiently consistent to satisfy the critical judgement of Carey Foster and the work was abandoned. He contributed a paper to the Physical Society in 1886 'On a Method of determining Coefficients of Mutual Induction' (Phil. Mag., 1867, [v], 23, 121-129), a method based on the comparison of the mutual inductance of two coils and the capacity of a condenser, which proved capable of yielding accurate results. His joint papers with Lodge and Fison have been cited on p.18. Among his other publications were further articles on Heat, Thermodynamics, Electricity, and Magnetism in later editions of Watts's 'Dictionary of Chemistry. He collaborated with Dr. E. Atkinson in an Elementary Treatise of Electricity and Magnetism, based on Joubert's 'Elementary Treatise of Electricity', and with Porter in a carefully revised and enlarged second edition, published in 1903, which avoided all but incidental reference to magnetic poles; a third edition appeared in 1910.

Becoming a member of the British Association in 1857, he served on a number of its committees, and was treasurer from 1888 to 1904. He was one of the founders of the Physical Society, which held its first meeting in 1873, and he was President from 1887 to 1889. He acted as President of the Society of Telegraph Engineers in 1880 and 1881. Elected to the Fellowship of the Royal Society in 1859, he served as one of the Vice-Presidents from 1891 to 1893 and from 1901 to 1903, and he took a keen interest in the work of the Kew Observatory Committee of the Society. Honorary degrees of LL.D. from Glasgow University and D.Sc. from Manchester were conferred upon him. A portrait of him hangs with those of other College dignitaries in the Old Refectory, and there is a delightful photograph of him sitting at his desk in the department (reproduced by H & N 127; 84).

Carey Foster was not a good lecturer owing to his nervous manner, and a reluctance to be content with a simple statement that he knew to be but an approximate expression of a truth, and to adopt the customary method of illustrating physical laws by means of simple, although entirely imaginary, experimental data. His use of actual results of laboratory measurements and laborious computations were only appreciated by the more dedicated students, who learnt to revere exact expression and regard it as the heart of scientific knowledge. They continually brought their difficulties to Carey Foster and were encouraged to do so by his unlimited patience in dealing with them. It was not unusual to find him surrounded by a small group of students engaged in earnest discussion half an hour after the end of a lecture. His enthusiasm for teaching and his patience in dealing with the smallest details were also evident in the students' laboratory. Having given a lecture in the morning and having a lecture for senior students in prospect at the close of a long afternoon, he would often help some duffer in difficulties in the laboratory, devoting the best part of an hour to the details of a simple experiment in physical measurement. Indeed on these occasions there was the danger of his love of accurate detail leading him not only to perform the experiment himself, making all the observations, but to carry out the necessary computations, while the student looked on wonderingly, as from a distance. Fison (op. cit. 424-5) concludes this account of Carey Foster as a teacher in these words "It may be that some who have worked in the old laboratory at University College in those days have preserved the scraps of paper covered with logarithmic calculations that Carey Foster often left on the benches, all executed in his wonderfully neat writing, as a memento of the most patient of teachers and most lovable of men, but such prescience is rarely bestowed on youth".

Fison (op.cit.423) writes of William Grant as follows:-
"For some years, the only apparatus available was of the simplest character, but instruments were being constantly designed by Carey Foster himself, whilst the designs were executed by a clever mechanic, William Grant, who acted as his assistant during the whole time of his professorship, and without whom no reference to the laboratory would be complete. Grant, who was quite a character in his own dour way, became a permanent feature of the Physical Department. His love of the apparatus, so much of which he had constructed, and the agony he experienced in seeing it misused, made him a source of terror to all students other than those few who proved themselves worthy to be entrusted with it; whilst many will remember with humiliation his lofty refusal of the tip that was occasionally offered , either from gratitude or from a desire to acquire merit. He was one of the most faithful of servants, and was devoted to Carey Foster, whilst each regarded the other with a simple affection of which both alike were worthy." Wood who knew Grant during the last three years of his service writes "He was then rather a dour old man, white and waxen of skin, with a well-kept beard which continued the contour of his face. Much troubled with phlegm on his chest, he badly needed a portable spittoon. He was an expert photographer specialising in the photographs of animals at the zoo, but unhappily, broke all his negatives before leaving College. The Library has a print of the front quadrangle taken in the 1880's which he gave to Dr. Rankine before he left. It seems that when he retired, a few members of the staff joined to present him with a portrait - almost certainly a large framed portrait of himself - which the Provost sent to him in Scotland with a letter inviting him to write up any memories he might have of his many years at the College. On Nov. 20, 1913 he wrote to 'Dr. Foster' thanking him for the gift and enclosed with the letter a thirty page manuscript dealing with the history of the College in general and of the Physical Department in particular."

The framed photograph of Grant by Elliott & Fry, bearing the inscription,"William Grant - Assistant in the Physical Laboratory U.C.L. - 1866-1913" is now in the department.

Wood repeats a story told to him by Dr.A.O.Rankine - "Carey Foster bought a Kelvin Quadrant Electrometer from Kelvin & White, the makers in Glasgow. (It would appear from the 1865-73 Catalogue that this electrometer was bought in 1870 and cost £28:10:0). It was considered too delicate to be sent in the usual way and Grant went to Glasgow to fetch it. He nursed it on his knees throughout the journey home, and, once safely in the laboratory, thought it too precious to be used. Later, Trouton, who became Professor in 1902, decided that it should be used in the students' laboratory. Grant was furious and became so angry that he threatened to report the Professor to the College Committee. Thereafter Grant's love turned to hate and it was not long before it met with an accident which led to its destruction - (apparently a dish of strong sulphuric acid put in its case to absorb moisture was left too long and overflowed)". (W.28-9).

Hugh Longbourne Callendar, M.A., F.R.S., was appointed to fill the Quain Chair for a period of seven years from the end of the session in June 1898. He was the eldest son of the Rector of Hatherop, Gloucestershire, born on 18 April 1863. According to his son's fascinating account of his life and work (Phys. Bull., April 1961, 87-90), he was an abnormally precocious boy, writing Latin prose before breakfast every day at the age of ten; being very good at mathematics; and having outstanding practical skill, manifested by the construction of a telegraph, which he used for sending messages in Morse code around the rectory, a Rhumkorf spark coil and a Wimshurst machine - all these without any help round about that early age. At eleven he won the first foundation scholarship to become the youngest boy at Marlborough College; he was Senior Prefect at sixteen, and he won every prize for which he entered, becoming top of school in Classics and Mathematics, yet being active in all games and representing the school in gymnastics and shooting. Acquiring a microscope, he studied geology, botany and biology, preparing hundreds of beautifully mounted slides, which he showed to his children in later life. Being in charge of the telescope presented to the school, he explained the wonders of astronomy to parties of masters and boys assembled on the roof at night. At school he invented the very first fountain pen, devised a system of shorthand, made an apparatus for the simultaneous recording of the force and direction of the wind, devised a system for testing sight and colour blindness by means of a spectroscope, and invented a new kind of vernier telescopic rifle sight, with which he won the Prince of Wales Cup at Bisley.

He entered Trinity College Cambridge in 1882 taking all available scholarships to read Classics and Mathematics. In 1884 he obtained first-class honours in Classics and he became sixteenth wrangler in 1885. Although working 10-12 hours a day, he usually took two hours off in the afternoon not only to keep fit but to excel in sport - representing the university at gymnastics and lawn tennis, and captaining the lacrosse team and shooting eight. In October 1885 he joined the Cavendish Laboratory and, at J. J. Thomson's suggestion, started research work on the variation of resistance of platinum as a means of measuring temperature, his working bench being a windowsill in a passage. Starting where Siemens had left off, he presented his results to the Royal Society on 10 June 1886 and patented his thermometer in 1887. In his autobiography J. J. Thomson says that Callendar was the most brilliant of all his research students during 40 years teaching at Cambridge. He was "an intellectual 'Admirable Crichton' who did everything well. In less than eight months he obtained results of absolutely first class importance. He gave to physics a new tool to determine temperature with an ease and accuracy never before obtainable and he was the first to suggest, from his experiments, the existence of super-conductivity of metal at or about the absolute zero". Incidentally having been taught Callendar's shorthand, he then used it for the rest of his life.

Elected a Fellow of Trinity College in 1886, Callendar not only continued his research work but studied both law and medicine, including 'walking the wards'. In 1889 he published his new Cambridge System of Shorthand and in 1890 he arranged for the Cambridge Instrument Company to start to manufacture his patented instruments as they came along - the platinum resistance thermometer, the temperature indicator, the recorder (which was the first electrical instrument to use the servo principle), the precision resistance bridge etc., there being in 1891 no less than nine original patents in different scientific fields. For the standardisation of his platinum resistance thermometer against the gas thermometer, with typical ingenuity he sealed the platinum spiral inside the bulb of the gas thermometer. His determination of the B.P. of sulphur with E. H. Griffiths in 1891, 4 degrees lower than the value previously accepted, was only 0.07 deg. different from the value of the sulphur point adopted on the International Temperature Scale, established in 1927. This scale from the ice point to the F.P. of antimony was based on the quadratic formula of Callendar, the constants being determined at the ice, steam and sulphur points; a quadric formula was used to extend the scale down to the B.P. of oxygen. His compensated constant-pressure air thermometer was devised in 1891.

From 1891-3 Callendar was Professor of Physics at Royal Holloway College and in 1893 he went to McGill University, Montreal to take charge of the new Macdonald Physics Building. There he worked on the theory and practice of the steam engine, his paper on the subject with J. T. Nicholson, The Law of Condensation of Steam, when read to the Civil Engineers in London being hailed as the most important on the subject ever presented to the Institution. He also devised a method of determining the total heat of steam by means of the differential form of the throttling calorimeter. At McGill he developed the continuous flow calorimeter, which he had invented in 1886, and with H. T. Barnes determined the variation of the specific heat of water with temperature, leaving Barnes to publish the results. In 1898 when he was offered the Quain Chair at College, McGill tried to retain his services by offering him the Professorship of Astronomy as well as that of Physics at nearly double his salary. However he decided to come to London and his successor at McGill, Rutherford, commented
"McGill (to which I have been appointed) is a very important place for Callendar (the previous Professor) was an F.R.S. and a Fellow of Trinity and I will be expected to do great things. I think my appointment is a much discussed matter at Cambridge as Callendar was considered a very great man ­ Callendar here (Rutherford had now arrived at McGill) was considered a universal genius and I gain a sort of reflected glory by carrying on with things Callendar was able to do. The trouble is that Callendar left such a reputation behind him that I have to keep rather in the background at present". (Rutherford's Life and Letters, Eve, 54-68).

At College Callendar continued the programme of lectures and practical work arranged by Carey Foster, taking over Carey Foster's lecture courses on Experimental and Senior Physics, each involving four lectures per week throughout the session. He published some fifteen articles and papers, including two of his most important papers, namely 'Thermodynamic Properties of Gases and Vapours' deduced from a modified form of the Joule-Thomson Equation (Proc. Roy. Soc., 67, 226-286), in which all the thermodynamic properties of steam were expressed by means of consistent thermodynamic formulae, and 'On the Thermodynamical Correction of the Gas Thermometer' (Proc. Phys. Soc., 1901, 18, 282-334), which contained the first accurate calculation of the absolute zero of temperature, namely 273.10 to within 0.02 C. The articles were for the Encyclopaedia Britannica on Heat, Thermodynamics, Calorimetry, Thermoelectricity, Vaporization, etc. and they appeared in various editions from 1902-59. Eumorfopoulos published one paper with Callendar on the thermal expansion of platinum and silica; all his subsequent research reflects Callendar's influence, both men delighting in experimental work, especially precise thermal measurements.

In connection with the special appeal launched by the College in May 1902, Callendar referring to Carey Foster's professorship of thirty three years wrote:-
"In this period not only did the science of Physics undergo enormous development and extension, but the methods of teaching and study underwent great change. In 1865 teaching was purely oral, and so far as it was experimental, the experiments were made entirely by the professor. In 1866, Foster opened the first Physical Laboratory for students in Britain south of the Tweed. The available space was small and the instrumental appliances most meagre, but the attempt was at least a recognition of the direction which physical teaching ought to take, and it was possible as time went on gradually to enlarge the laboratory and improve the equipment. The rooms to which the physical department was transferred in 1893 constituted at that time the best physical laboratory in London, possibly in England.

So great, however, has been the development of the science, and so important and varied its applications, that already considerable extensions of the Department are required. In the first place, it is now hardly possible for one Professor to do equal justice to all parts of the subject-Heat, Light, Electricity, Magnetism, etc., at any rate so far as advanced work is concerned. It is moreover of the highest importance that the heads of the department should be able to devote the greater part of their time to research in the work for which they are fitted by their special attainments, and this can only be accomplished by the provision of capable junior teachers (lecturers and assistants) who can undertake the greater portion of the elementary work.

The following extensions of the Department are therefore proposed:-

A. Staff.

An additional Professor at	£300 a year.
A Lecturer for elementary students at	£200 a year.
An additional Demonstrator at	£150 a year.

B. The Physical Laboratory requires enlargement especially to provide facilities for research. At the present time the Professor has no space save for this purpose apart from that appropriated for the use of students. Several additional rooms are required for special purposes, such as experiments on heat and other of the more refined observations. This additional accommodation can be provided by building another storey to the present Physical building, and also extending the department into the basement of the main (East) wing. The total cost of these alterations and additions, with a proper equipment of the entire laboratory, would not exceed £10,000.

C. Maintenance. The present grant (an endowment from the Quain Fund of £300 a year for the Professor and £200 a year for expenses, more than half of which goes to pay a mechanical assistant) is even now inadequate for the maintenance of the department and the purchase of apparatus. For this purpose an additional endowment of £300 a year is required.

The total sum required for enlarged and endowing the Physical Department is therefore:-

Staff	£22,000.
Laboratory and Maintenance	£20,000.
Total Capital Sum	£42,000."

(The Needs of University College, London: with some account of the previous history of the college and the part it has played in the increase of knowledge; being An Appeal for the Endowment of advanced University Education and Research in London, 1902).

Callendar did not stay to see the outcome of his appeal since he accepted an invitation to succeed Sir Arthur Rucker as Professor of Physics at the Royal College of Science. The Physics Department at the Royal College was housed in the Huxley Building in Exhibition Road, but the building in the Imperial Institute Road was then being designed and Callendar was able to help design the new physics laboratories which were opened in 1906. Wood attended his third-year lecture course in the 1907-8 session at the Royal College and sheds an interesting light on his style and method.

"He spoke clearly and fluently but confined himself to topics in heat which he had first hand experience. He was tall and dark and had a deceptively languid manner. This gave point to a story he told with somewhat impish pleasure. Having occasion to look through Barnes' paper on the continuous calorimeter in the Science Library copy of the Royal Society Transactions he found, in the margin, opposite Barnes' statement that he, Callendar, had left Barnes to complete the work, the pencilled comment 'Too tired'! He then explained that he allowed Barnes to publish as the single author because it would help him to obtain a Chair. He devised a system which ensured that his students read up the subject and obtained experience in answering examination questions. Each fortnight they were instructed to read specified parts of a text book. On alternate Wednesday afternoons they sat for a three-hour examination on this reading and on the lectures he had given. On the other Wednesday afternoons he went through the questions and commented on the scripts which he himself had marked. Not many Professors would have taken that trouble! " (W.42-3).

Callendar occupied the chair at South Kensington until his death on 21 January 1930. Elected F.R.S. in 1894, he was awarded the Rumford Medal of the Royal Society in 1906. He was Treasurer of the Physical Society for ten years from 1900, President in 1910-12, and was awarded the first Duddell Medal in 1924. Serving on the Council of the British Association from 1900 to 1906, he became President of Section A in 1912. In 1920 he was made C.B.E. for his war work with the Board of Inventions and Research. During the last few years of his life, he studied "knock" and the mechanism of anti-knocking agents in petrol engines, directing research for the Air Ministry. He was the foremost authority on steam and published 'The Properties of Steam' (1920), several editions of 'Steam Tables' (1915, 1922 and 1927), and 'A Manual of Cursive Shorthand' (1889) as well as many scientific papers. His final achievement announced in his Hawksley lecture to the Institution of Mechanical Engineers (Proc. I. Mech. Eng., 1929, Nov. 1st., 811-38) just before he died was to carry his high pressure temperature experiments right up to the critical point for water and steam, which had never been done before. He then proposed three simple equations, consistent with the laws of thermodynamics, which should suffice to define all the properties of steam for international standard purposes and which should be of the greatest assistance both to the scientist and to the practical engineer. Callendar was an exceptionally simple-hearted and kindly man, ever ready to give his assistants more than full credit for anything they did. He raised the standard of everything he touched in physics and engineering beyond anything that had gone before.

Frederick Thomas Trouton, M.A., F.R.S., was appointed Quain Professor to succeed Callendar in 1902. He was born in Dublin on 24 November 1863, the youngest son of Thomas Trouton, a wealthy and prominent citizen. Entering Trinity College Dublin from Dungannon Royal School, he performed brilliantly as an undergraduate in both engineering and physical science, being awarded the Large Gold Medal, an honour rarely bestowed for work in science, and graduated M.A. and D.Sc. While still a student he pointed out the relation between the molecular latent heats and boiling points of various substances, which became known as Trouton's Law, namely L/T, the change of entropy per mole in evaporation at the boiling point, is constant; although not exact, the relation is a useful rule. Trouton is probably now best known for this discovery, the result of an afternoon's manipulation of data from a book of tables! Later he returned to the study of latent heats and determined the latent heat of evaporation of water from saturated salt solutions, obtaining agreement with thermodynamically based values. As an undergraduate Trouton also participated in the surveying of a railway.

Appointed Assistant to Prof. G. F. FitzGerald in 1884, he was elected a Fellow of the Royal Society in 1897 and became Lecturer in Experimental Physics in 1901. FitzGerald inspired much of his earlier work, including that begun in 1886 on the experimental verification of Ohm's law for electrolytes. As Porter in his Royal Society obituary notice of Trouton points out, FitzGerald was one of the few physicists who took Maxwell's electromagnetic theory of light seriously, and consequently when Hertz began publishing his investigations on electric waves, FitzGerald was one of the first to give a detailed account of them at the British Association meeting in Bath in 1888, and to stimulate laboratory work to extend and interpret them. Trouton worked with him in studying the reflection from insulators such as glass and paraffin wax; they exhibited "thin film" phenomena and settled the long-disputed question as to the azimuth of vibration in relation to that of polarisation. Trouton's experiments on reflection at the polarising angle from the surface of a bad conductor proved that when the electric vector is in the plane of incidence the reflection is bad, but reflection occurs at all angles when this vector is at right angles to that plane. He also showed that a small reflector, i.e., a disc approximating to the pole of a wave, reflects a wave nearly a quarter of a period in advance of the whole reflected wave, and thereby justified experimentally the "quarter-wave advance" introduced by Stokes in connection with Fresnel's treatment of a primary wave as the resultant of effects from elementary wavelets or secondary waves.

A series of experiments on the relative motion of earth and ether also followed from FitzGerald's influence. The underlying idea of the first experiment was that a charged condenser moving through the ether with its plates parallel to the direction of motion possesses magnetic energy as well as electrostatic energy on the basis of a moving charge being equivalent to a current element, and the source of this energy would be due to a mechanical drag on the condenser during the process of charging. Trouton devised an experiment to test this conclusion and initial indications of a negative result were apparent when FitzGerald died. However he had expressed the view that if such a result was sustained by further work it could be attributed to a contraction of the linear dimensions of the condenser in the direction of motion through the ether leading to a diminution of electrostatic energy sufficient to produce the energy for the magnetic field. Further consideration of the problem convinced Trouton that a turning-impulse rather than a translational one was to be expected, the extra energy gained in turning the condenser through ninety degrees coming from the work required for the rotation; in any intermediate position a couple would be experienced, the maximum value being in the 45-degree position. Assuming a positive result to be obtained, Trouton envisaged the possible building of a machine consisting of condensers for utilising the vast store of energy in the earth's motion through space.

This investigation was the first undertaken by Trouton on taking up the Quain chair. In conjunction with a research student, H. R. Noble, a mica condenser was suspended by a fine wire with its plates vertical, the charges being led onto the plates through this wire and another wire hung from beneath them and dipping into a liquid terminal. The very thorough investigation extending over many months leading to negative results is recorded in the Philosophical Transactions of the Royal Society, 202A, 165-181, 1904. Assuming FitzGerald was right in his contraction hypothesis, Trouton sought for more positive evidence of its truth. In 1908 with A.O.Rankine, an old student appointed Assistant in 1904, an attempt was made to measure the change of resistance of a wire when parallel and transverse to the ether drift. Four rectangular coils were wound, mounted on a common stand and connected in such a way that they formed a Wheatstone network, the wires forming opposite arms of the bridge being parallel. The bridge was balanced when the wire in two of the coils was at right angles to the resultant drift and then the whole assembly was rotated through 90 degrees and the change of balance tested. Once again every realizable precaution was taken only to lead to a negative result as recorded in Proc. Roy. Soc. 80A, 420-435, 1908. However these researches placed Trouton in the great tradition of nineteenth-century British physics, he being perhaps the last of the well-trained ether mechanists.

For some years the viscosity of quasi-solids interested him and much ingenuity was displayed in investigating it; with E. S. Andrews he applied the bending beam method to pitch, the torsion method to soda glass at different temperatures, and the falling sphere method to shoemakers' wax in which the velocity of a ball bearing was determined by means of X-ray observation as the ball descended 1.8 cm. in a fortnight. This X-ray method for the examination of opaque media was introduced by Trouton. While in Dublin Trouton had begun work on the adsorption of water vapour by flannel, glass and other substances with the view to constructing a recording hygrometer based either on the change of weight or, in the case of glass, the change of electrical resistance between two wires fused on the surface. Although this aim was not achieved, it led to a long series of investigations on adsorption in which several curious effects were observed, e.g., when the amount of water admitted to a vessel filled with glass wool was gradually increased, the equilibrium pressure of the vapour varied continuously, but the the curve obtained by plotting pressure against water-content had a marked kink in it, analogous to the kink given by van der Waals' equation for gases. A curious consequence was that it could be arranged for a glass surface holding a certain amount of water vapour to have a lower vapour pressure than a drier surface. Analogous effects were observed with phosphorus pentoxide; if very dry and ordinary phosphorus pentoxide were placed side by side under a bell jar and water was admitted in small quantities day by day, the ordinary oxide got continually wetter while the dry remained dry except for a few specks probably due to dust or other impurity, since it was too dry to take up moisture at all. Trouton was working on the general phenomena of adsorption with the help of his assistant, H.Burgess, when he first felt ill. It was established that the effects observed with glass and water vapour were not peculiar to them since similar effects were obtained with the adsorption by silica of the salt from various salt solutions. A brief account of this work was given in Trouton's Presidential Address at the Australian Meeting of the British Association in 1914 - an address read for him since he was then too ill to travel.

It will be recalled that the College became incorporated into the University during Trouton's tenure of the Quain chair. Under the University Regulations in order to qualify for registration as an undergraduate student it was necessary to pass the Matriculation examination. This involved passing in five subjects at the same examination, failure in any one requiring resitting the whole examination again. Three of the five subjects were compulsory, namely English, Mathematics and a foreign language, the other two being selected from a long list. The Matriculation courses listed by the department were X1 Mechanics; X2 Sound, Light and Heat; X3 Electricity; and they were given by H. J. Harris, B.A., an assistant in the Mathematics Department! Incidentally this examination, first held in November 1838, was held for the last time in June 1951. For some thirty years prior to the latter date, many school pupils gained exemption from matriculation on the basis of the requisite credits in the School Certificate Examination. Having matriculated a student could be registered for a three-year degree course. In the first year four subjects were studied and were required to be passed in the Intermediate examination taken at the end of the session. However a student with a marginal failure in one subject and a satisfactory performance in the other three could be "referred" in the one and allowed to retake it at the end of the second session. The Intermediate courses offered by the department were Y1 Elementary Mechanics still given by Porter, and Y2 Experimental Physics now taken by Trouton, these courses being renamed Junior Mechanics and Junior Physics in the 1908-09 session. The degrees available were a B.Sc. Pass degree in three subjects, e.g., Physics, Chemistry, and Mathematics, and a B.Sc. Honours degree in one main subject and a subsidiary subject, e.g., Physics with Mathematics; Chemistry usually with Physics. Mathematics was special in that it required no subsidiary subject. Z1, the Senior Physics course, given by Trouton covered I Molecular Physics - Elements of Elasticity, Capillarity, Dynamical Theory of Gases, II Heat and Thermodynamics, III Sound and Light, IV Electricity and Magnetism, there being four lectures a week during the two sessions of the course; I became General Properties of Matter in the 1909-10 session. A, Higher Senior Physics, supplemented Z1 and was taken concurrently with it by the honours students, there being two lectures per week given by Trouton and Porter. Honours, Pass, and Subsidiary students worked in the senior laboratory on three days, two days, and one day per week respectively. Other courses provided by the department were a special course on Thermodynamics for second-year Engineering students and one on Physics for first-year Medical students.

In the long vacation of 1905 the department was enlarged, an additional storey being built to the Carey Foster laboratory and the large lecture theatre being reconstructed with a suitable lecture bench and seating accommodation for 132 students. On the upper floor there was also the smaller lecture theatre seating some 70 students, an apparatus room, a preparation room, and a common room for the professor and his academic staff. In the western half of the basement there was a laboratory for 36 intermediate students working in pairs, a research laboratory for Eumorfopoulos, and a workshop; the eastern half was used as a laboratory for senior students, who also worked on the ground floor of the Carey Foster laboratory. A lobby leading from the senior laboratory contained a sink and an ice-chest and gave access to an accumulator room, equipped with 60 large open-cell accumulators, and thence to another small room (really part of the Birkbeck building).

Wood who joined the academic staff as an assistant in October 1910 gives a graphic account of conditions in the laboratories at that time. During their 1¹/₂ hour period of practical work the intermediate students worked in pairs, each pair performing the same experiment(s) in the same period. The apparatus was put out by the laboratory steward and instructions for performing the experiments were written on a blackboard beforehand by the assistant in charge of the class. Before work began the assembled class was informed about procedures and precautions - how to use a micrometer screw gauge or a Fortin barometer, how to attach a wire to a screwdown terminal or which side of a concave lens should be viewed to see the virtual image of a pin! These introductory talks saved time during the period and enabled staff to discuss any problems individual students had met in reading or in exercise work. Details of apparatus, procedure, and results were written in approved note-books and handed in after a lecture two or three days later together with exercise books containing answers to three numerical problems set each week. These books were marked and returned at the next practical period. Until the outbreak of war in 1914 Wood marked some 300 books each week. Apparently causes of error in the results of experiments could usually be easily located since Eumorfopoulos had prepared elaborate tables for each set of apparatus giving correct measurements and the results obtained on the basis of correct evaluation of incorrect data.

Duplicated lists of students due in the senior laboratory each day of the week were prepared at the beginning of each session, and round about 5 p.m. each day Eumorfopoulos would allot the experiment to be carried out by each student due in the laboratory the next day. Records of the work done were kept on stiff cards about 25 cm. by 7.5 cm. in size, each card labelled with student name, course, and day(s) of attendance in the laboratory. The cards were ruled in columns, one for each branch of the subject and in rows showing the number of the experiment, e.g., P for Properties of Matter - P5, Compound Pendulum, so that dates of performance, accounts and marks could be seen at a glance. Instructions, hand-written by Eumorfopoulos on blue linen-backed paper, were provided for each experiment so that students could start work without waiting for verbal instructions from members of staff on duty in the laboratory. Later when there were more students manuscripts were typed and pasted on cardboard, and the allotted experiments were displayed on sheets of millboard on a notice board.

The adequate laboratory equipment was well designed to provide good training in laboratory techniques. Such apparatus as could be made in the departmental workshop had been made by Grant, e.g., two good Helmholtz twin-coil galvanometers. In the senior laboratory there was a reasonable supply of resistance boxes, including a Callendar-Griffiths bridge and a Thomson-Varley slide, and of optical appliances - travelling microscopes, cathetometers and spectrometers. Moving-magnet mirror galvanometers were used in many of the electrical experiments with lamps and scales, the lamps usually being of the Nernst filament type, although one with an oil lamp was occasionally recalled into use. (W. 51-53).

Research was also actively pursed by academic staff and post-graduate students. In 1906 friends of Carey Foster set up the Carey Foster Fund for a Research Prize in Physics to commemorate his services to the College and to education in general. The prize took the form of books or instruments or apparatus to the value of £5 and was awarded by the Quain Professor to a student in the department engaged on research during the session preceding the award of the prize. The first prizeman was E. P. Metcalfe who had graduated with first-class honours in 1904 and was working with Clive Cuthbertson on the refractive indices of gaseous potassium, zinc, cadmium, mercury, arsenic, selenium and tellurium. In July 1907 Trouton, who had been giving £100 to the department for buying apparatus, transferred this sum to establish two scholarships for research in physics valued at £60 and £40 per annum and guaranteed for five years. The first scholar was E. N. da C. Andrade, who had gained first-class honours in the external examination in 1907, and received £60 in December of that year for his work on the flow of metals such as lead under constant stress. The guarantee was renewed in the 1912-13 session; moreover Professor and Mrs. Trouton in 1914 gave £300 for supplementing the apparatus, and £114 8s for special service in the department.

There were some twenty publications by Assistant Professor Porter over a very wide field including patterns formed by diffraction gratings, resolving power of a spectroscope, growth of photographic images, electric splashes on photographic plates, lagging of wires and pipes, inversion points of fluids passing through a porous plug, solidification of helium, osmotic pressure of compressible solutions; with post-graduate students there were the diffraction of light by particles whose size is comparable with the wavelength (with B. A. Keen), an experiment on the rotatory polarisation in liquids (with E. T. Paris), and he also suggested and supervised F. Simeon's work on the viscosity of calcium chloride solutions and on the relative thermal conductivities of solid and liquid sodium. Eumorfopoulos published his paper on the expansion of mercury using a large silica weight thermometer, and those on the boiling point of sulphur using a Callendar compensated gas thermometer, filled with nitrogen, probably the only one used in this country. Rankine, who gained first-class honours in 1904 and was appointed Assistant in the following session, first collaborated with Trouton on a study of the stretching and torsion of lead wire beyond the elastic limit; he then published papers on the decay of torsional stress in solutions of gelatine and the behaviour of over-strained materials; there followed the work on ether drift, and then his closed-circuit method for the viscosity of gases, especially those available in only small quantities, and its application to the then rare gases. Clive Cuthbertson, who after obtaining his B.A. at University College, Oxford, joined the Indian Civil Service but was forced to retire owing to ill-health; he was a student in the department from 1897-99 and was Assistant Private Secretary to the Marquess of Salisbury from 1900-02, returning to the department for research in 1902. Working with a Jamin interferometer in an upper room in the Carey Foster laboratory, he carried out an extensive series of investigations on the refractive indices of gases with the specific objective of understanding the underlying mechanism. His many papers, alone and in collaboration with others including his wife, Maud, and research students, "placed the question of the refractivities of the elements on a totally new basis. --- His work has now become widely known and recognised as the standard work on the subject." (Trouton's citation on his election to the Fellowship of the College in 1908). With Porter he endeavoured to measure the refractive index of radium emanation of which only one-third of a cubic millimetre was available - and no index for a gas had ever been determined with less than ten cubic centimetres; in spite of this an approximate value was obtained, difficulties other than those arising from the small quantities available making it impossible to obtain precise values. However it was clearly shown that the value was the largest of the non-valent group. Shortly after the outbreak of war he gave up research and became a Staff-Sergeant, Instructor of Musketry at Hythe, and then from 1915 to 1919 a temporary clerk in the Foreign Office. He was elected F.R.S. in 1914 and made O.B.E. in 1918. Percy Phillips, who had worked with Poynton in 1905 on an experiment to determine whether change of temperature had any effect on weight, worked on the recombination of ions and then on the viscosity and refractivity of carbon dioxide near its critical point.

Wood recalls Trouton as a "charming and kindly man, a good story teller but a hesitant lecturer. Everyone liked him but his discipline in his intermediate lectures was notoriously bad. He would spell 'lens' with a terminal 'e' and 'dew' as 'due', while another of his peculiarities was an inability (or unwillingness) to distinguish between electric intensity and electric induction, the difference involving the factor 4/K or its reciprocal. He would say 'Ignore this factor for the time being in your problem, and then at the end decide how to put it in. If you think it should be 4/K put it in as K/4 and vice versa. (A.O.Rankine in a letter). He introduced the 'real is positive' sign convention in his lectures on geometrical optics and it is possible that it originated with him or with FitzGerald." (W.44). During Trouton's illness Porter was acting head of the department and in the autumn of 1914 Dr. Percy Phillips was appointed to the academic staff and gave most of Trouton's lectures. Trouton resigned from the Quain chair at Christmas 1914 and lived in retirement at Tilford in Surrey, and afterwards at Downe in Kent until 1922, when on 21 September he died almost a month before his 59th birthday. He kept all his mental faculties little impaired until his death but paralysis of both legs rendered him incapable of locomotion during the last five years of his life. Despite this incapacity and the loss of his two eldest sons in war service, Trouton remained unbroken in spirit, his wit and charm undampened until extinguished in death.

William Henry Bragg, M.A., D.Sc., F.R.S., Cavendish Professor of Physics at Leeds University, was appointed to the Quain Chair as from 1 September 1915, Porter having been in charge of the department from January of that year. Bragg was born on 2 July 1862, the son of a yeoman farmer at Westward, near Wigton in Cumberland. At the age of seven he went to school at Market Harborough, being one of the six boys with which the old grammar school opened after re-establishment by his Uncle William. In 1875 he entered King William's College in the Isle of Man and rose to become head of school. Early in 1880 he tried for a scholarship at Trinity College, Cambridge and was awarded an Exhibition, but was advised to return to school for a year since he was only seventeen. The following year he tried again but didn't do so well; however he was elected to a minor scholarship on the strength of his previous performance."In his notes Bragg puts his 'stagnation' down to a storm of religious emotionalism that swept through the school - the boys were scared of eternal damnation and of hell fire, and very much exercised as to what they should do to be saved. 'It really was a terrible year' says Bragg, who, though essentially a religious man, adds, 'But for many years the Bible was a repelling book, which I shrank from reading'. This from his private notes, but the period evidently left a strong mark on his mind, for in the Riddell Memorial Lecture on 'Science and Faith', given in the year before he died, he says, 'I am sure that I am not the only one to whom when young the literal interpretation of Biblical texts caused years of acute misery and fear'." (Royal Society Obituary Notice by Andrade). At Trinity he obtained a major scholarship in 1882, was third wrangler in the Mathematical Tripos, Part I in 1884, and gained first-class honours in Part III in 1885. J. J. Thomson was appointed Cavendish Professor at the end of 1884 and Bragg attended his lectures among others during 1885. At the end of that year J.J. asked him if Sheppard, who had been senior wrangler in Bragg's year, was applying for the professorship of mathematics and physics at Adelaide, which had just become vacant on the resignation of Horace Lamb, who had held the post since the foundation of the university in 1875. Sheppard was not a candidate, but the query prompted Bragg to apply, and with two others he was interviewed by the electors - the Agent General (Sir Arthur Blyth), J. J. Thomson and Horace Lamb - and chosen for the post. Naturally Bragg was delighted; the salary of £800 a year, the prospects of a new country and being his own master thrilled him. Bragg had not studied physics, but apparently the electors supposed he would pick up the subject as he went along. Anyway he read Deschanel's Electricity and Magnetism while sailing to Australia.

The life there suited him down to the ground, his social gifts making him very popular. In 1889 he married Gwendoline, the daughter of Charles Todd, the Postmaster General and Government Astronomer of South Australia, who was elected an F.R.S. in that year and later became a K.C.M.G. Apparently Bragg at first was an unimpressive lecturer but by careful application he developed towards that past-mastery of the art which he afterwards attained. Moreover he became interested in experimentation and following Röntgen's discovery in 1895 he set up the first X-ray tube to operate in Adelaide, but he made no attempt to carry out any original investigation; in fact in his first eighteen tears at Adelaide he published only three minor papers on electrostatics and the energy of the electromagnetic field. In January 1904 the Australian Association for the Advancement of Science met in Dunedin, New Zealand, and Bragg gave the presidential address to Section A on "Some recent advances in the theory of the ionization of gases", a critical review of the field, the most pointed criticism being directed towards work on the scattering and absorption of the ionizing radiation by matter. A few months later some radium bromide was given to him and with the assistance of R.D.Kleeman he began his classical researches on the range of the alpha particle and the allied questions of the ionization produced by the particle and of the stopping power of substances. Publishing a paper every few months, he soon established himself as an original investigator of the first rank and in 1907, less than three years after the reading of his first original paper, he was elected an F.R.S., Rutherford, with whom he had corresponded freely on the alpha-particle work, being his proposer. There followed in 1908 the offer of the Cavendish professorship of physics at Leeds which brought him back to England.

At Leeds Bragg was first fully occupied with organizing the teaching of the laboratory. In 1912 his monograph on alpha rays was published under the title 'Studies in Radioactivity'. He began to be deeply concerned as to the nature of X-rays, a problem exercising the scientific world. The doubtful results of certain attempts to produce diffraction had militated against the general acceptance of a wave nature. Bragg inclined to the opinion that they were of the nature of a particle, an electrically neutral doublet. However von Laue's suggestion that the rays might be diffracted by a thin slice of crystal, confirmed by the experiment of Friedrich and Knipping, caused a sensation in the physical world in the Summer of 1912. Bragg's interest was immediately captured and Andrade (loc.cit.) quotes what he wrote in Nature in November of that year - " Dr. Tutton suggests that the new experiment may possibly distinguish between the wave and corpuscular theories of the X-rays. This is no doubt true in one sense. If the experiment helps to prove that X-rays and light to be of the same nature, then such a theory as that of the 'neutral pair' is quite inadequate to bear the burden of explaining the facts of all radiation. On the other hand, the properties of X-rays point clearly to a quasi-corpuscular theory, and certain properties of light can be similarly interpreted. The problem then becomes, it seems to me, not to decide between two theories of X-rays, but to find, as I have said elsewhere, one theory which possesses the capacity of both." Bragg's elder son, William Lawrence, had just graduated with first-class honours in physics at Cambridge and his father suggested that he should start research on X-ray diffraction. There followed the now well-known W. L. Bragg reflection law, based on the reflection of waves from parallel layers of atoms, a much simpler interpretation of the phenomenon than that based on interfering wavelets from a three-dimensional array of atoms. Collaboration between father and son led to the publication of their first joint paper, early in 1913 in the Proceedings of the Royal Society, which founded the science of crystal analysis by means of X-rays. Up to the outbreak of war in 1914 Bragg produced five further classical papers, in one of which he collaborated with Lawrence on the structure of diamond. The others dealt with the general technique of the X-ray spectrometer; the characteristic absorption of the different radiations and its effects; the structure of sulphur and quartz; and the general question of intensities. In these experiments Bragg used the ionization spectrometer to detect and measure the rays, his earlier work having taught him how to overcome the difficulties associated with this type of measurement. The work of the Braggs in the two years 1913, 1914 established the use of X-rays for the determination of the way in which crystals are built, and this was recognised by the award of the Nobel prize for Physics in 1915 to them jointly "pour leurs recherches sur les structures des cristaux au moyen des rayons de Roentgen". Bragg was a leading figure in Leeds University and became Pro-Vice-Chancellor; he continued his X-ray work into 1915, publishing e.g., a paper on the the spinel group of crystals. In July 1915 he was made an original member of the Board of Inventions and Research then instituted to give the Admiralty expert assistance in organizing and encouraging scientific effort in connexion with the requirements of the Naval Service, the submarine menace then becoming acute.

Bragg worked at College until April 1916 giving, e.g., the lectures on electricity to the B.Sc. Honours class. He then became Resident Director of Research at the Admiralty experimental station at Hawkcraig, but after many troubles largely within the Admiralty a laboratory was built for him at Parkeston Quay, Harwich, where he started work in 1917, having under him A. O. Rankine and other physicists. The departure of Rankine left Porter, Eumorfopoulos and Wood to carry on the work of the department, much depleted of students but still with the same number of classes. During this period the Admiralty took over part of the Carey Foster laboratory and incidently left behind 18 Tinsley galvanometers at the end of the war. During the course of the experiments and research on anti-submarine work principles were established and methods, as well as apparatus, devised which were of great service in the war against the submarine; in particular the hydrophone rendered outstanding service. In acknowledgment of his war work, as well as his scientific eminence, Bragg was made a C.B.E. in 1917 and was knighted as a K.B.E. in 1920.

Bragg and Rankine returned to College at the end of the war but Rankine, who had been made an O.B.E. for his war work, left at the end of the 1918-19 session to become Assistant Professor of Physics at Imperial College of Science and Technology. Bragg promptly started research, assembling a brilliant team of workers who occupied most of the Carey Foster Laboratory. It included W. T. Astbury, I. Backhurst, R. E. Gibbs, A. Müller, G. Shearer and Kathleen Yardley (later Dame Kathleen Lonsdale), who had so impressed Bragg by her outstanding performance in the London B.Sc. final examination in 1921. Some were appointed as demonstrators, others as research assistants paid a salary of £450 per annum. Since the equipment was scanty at first, most had to be designed and made. Continuously evacuated X-ray tubes, both hot wire and gas filled, were introduced and a self-rectifying gas tube was evolved, which gave useful service for many years. The ionization chamber was replaced by the photographic plate and the first attack on the structure of organic crystals was begun. Braun, who had worked alone in the workshop in Trouton's time, was transferred to the main College workshop, and replaced by a highly skilled instrument maker, C. H. Jenkinson, who came with Bragg and supervised, or made with one or two assistants, the new equipment. The workshop itself was moved to two large rooms adjoining the Birkbeck laboratory, one for metal and the other for wood work, access being gained through the accumulator room. For much of this work Bragg applied the powder method, whereas before he had worked with single crystals. His results on naphthalene and its derivatives were embodied in his presidential address to the Physical Society in 1921; he demonstrated that the benzene or naphthalene ring is an actual structure preserving its general form and size from compound to compound. This work was the starting point of the series of investigations on different classes of organic compounds which he directed afterwards at the Royal Institution. He also worked on the probable structure of ice, and at an annual dinner of the Alpine Club exhibited a model made of soft dental wax, which wilted as the evening became warmer. For the first time in its history the department began to make a major contribution to the advance of scientific knowledge and to become well known both in the world of science and in the outside world, just as the Department of Chemistry had become through the researches of Sir William Ramsay during his tenure of the chair of chemistry from 1887 to 1913. However Bragg's tenure of the Quain Chair was cut short in 1923 when on the death of Sir James Dewar he was elected to succeed him as Head of the Royal Institution.

Dewar was over eighty years old at the time of his death and there was much to be done in the way of reorganization at the Royal Institution. Bragg promptly directed the work of the Davy-Faraday Laboratory to the problems of crystal structure, having taken all his apparatus and entourage from College. He soon attracted other distinguished researchers to the laboratory which speedily became a world-centre of research. In 1919 Bragg had given the Christmas Lectures at the R.I. on 'The World of Sound'. One of his first tasks on going to the Institution was to give the series on 'Concerning the Nature of Things', and on two other occasions, namely at Christmas 1925 and Christmas 1931, he gave the lectures on 'Old Trades and New Knowledge' and on 'The Universe of Light'. Following the 1925 series Bragg took "Craftsmanship and Science" as the subject of his Presidential Address at the British Association in Glasgow in 1928. The Royal Society bestowed on him the Copley medal, its senior award, in 1930, having awarded him the Rumford medal in 1916. He was an honorary doctor of some sixteen British and foreign universities, and a member of the leading foreign societies. In 1931 he received the Order of Merit, and in 1935 at the age of seventy three he was elected to the Presidency of the Royal Society. During the early stage of the second world war he was chairman of several important scientific committees and held a number of other appointments as well as carrying out his duties at the Royal Institution. He even wrote a little book, 'The Story of Electromagnetism, to help boys of the Air Training Corps in their studies. For some time his heart had been giving him trouble and he tried to avoid physical exertion, while remaining ever active in his mind. As late as December 1941 he wrote to Nature on the new phenomenon of extra reflections or diffuse spots in X-ray photographs. On Tuesday, 10 March 1942, he had to take to his bed, and two days later he died.

In his obituary notice Andrade writes inter alia "Bragg had an astonishing career. Up to the age of forty he never showed any desire to carry out original experiment. He then straightaway embarks upon a perfectly precise and important piece of work and within a few years his name is known wherever physics is seriously studied. He spends some years carrying out a careful series of experiments which can be interpreted to prove the corpuscular nature of X-rays, and he stresses this interpretation. He then himself conclusively demonstrates, by the work with which his name will always be associated, the wave nature of X-rays. He starts life as an extremely shy and retiring youth, never, apparently, quite at home in Cambridge, and in his old age becomes a national figure, at ease in all surroundings, whose personal appeal is known all over England."

In the Riddell Memorial Lecture on 'Science and Faith' given in the year before he died, Bragg says "I am sure that I am not the only one to whom when young the literal interpretation of Biblical texts caused years of acute misery and fear". However religion continued to be a strong influence in his life; devoid of dogmatism, he had a simple piety and was an enemy of unbelief; and something of his own belief is given in the aforesaid lecture.

Andrade concludes his obituary notice with "There was, we like to think, something peculiarly British about Bragg. His attitude towards physics was that characteristic of the great experimenters of our land, especially his strong pictorial sense. He was a lover of the traditions, especially those of the great institutions with which he was connected. His lack of pedantry, his gift for popular exposition, his strong feeling for the craftsman in factory and workshop are all characteristics which he shared with Faraday, with Tyndall, with J.J.Thomson. He was an ornament, not only of English science, but of English learning, a great teacher and a good man, whose death came as a personal loss to all those who knew him. With him went an outstanding representative of a great period of English physics." A chronological bibliography, prepared by Kathleen Lonsdale, is appended to Andrade's obituary notice; it runs from 1891 to 1942 occupying eight pages. There is a reproduction of a photograph of Bragg seated at his desk in the Carey Foster laboratory in Harte & North (274;153).

At the end of the war special arrangements were made for students to start their intermediate courses in January 1920 and take a special intermediate examination in the following August. Students, who had left College for war service after passing their intermediate examinations, were released in time to return in the January; they were allowed to sit their final examinations in the autumn of 1920. Amongst the latter were Backhurst, Gibbs and W. S. Stiles, who having been appointed Demonstrators for the 1920-21 session, were given leave of absence until completion of their final examinations in November.

To cope with the increased number of students the senior laboratory was extended by taking over the junior laboratory which adjoined it. In 1920 the disused All Saints Church, which butted on to the Carey Foster laboratory and had been bought by the College in 1912, was made available for the intermediate students, S. M. Dhar B.Sc. being employed as a demonstrator and Miss L. Kilpack as laboratory steward.

This was only a temporary measure since the church was due to be converted into the Great Hall as a memorial to the students who had lost their lives during the war. The building of the new Anatomy block and its occupation in 1923 provided a longer term solution. The large room adjoining the senior laboratory northwards, which had been the Anatomy dissecting room; the old Birkbeck laboratory, which had been built in 1845 for G.Fownes, the first holder of the chair of Analytical and Practical Chemistry, together with the small rooms between it and the workshop, were allocated to the department. The floor of the dissecting room was lowered to the level of the basement since it was said that students had habitually dropped pieces of their dissections through gratings in the stone floor on to the ground below. It was redesigned as a physical laboratory by F. M. Simpson, the Professor of Architecture, who incidentally made no provision for ventilation in a new glass roof. The Birkbeck laboratory was renovated and a short staircase provided giving access to it and the workshop from the new physical laboratory. When all these alterations had been completed the intermediate practical classes reverted to the basement, the senior classes extended into the new territory, and the Carey Foster laboratory was left free for research.

Mrs. E. Wood, wife of Orson Wood, was a temporary assistant during the 1918-19 session, and in the following session G. A. Sutherland, B.A., and L. H. Clark, B.Sc., were appointed Assistant and Demonstrator respectively. In the summer of 1920 Eumorfopoulos retired from teaching to concentrate on his involvement with the Union Society - having been Honorary Treasurer since 1912 - and on his porous-plug experiments; he became an Honorary Research Assistant, Wood assuming charge of the teaching laboratories. As mentioned earlier Backhurst, Gibbs and Stiles were appointed as Demonstrators and Dhar as Assistant for the 1920-21 session, Dhar replacing Clark who left to take up a post as physicist at the Postgraduate Medical School, Hammersmith. In the following session Sutherland, now an M.A., became an Assistant Lecturer, Astbury became the fourth Demonstrator and J. H. Smith, B.Sc., replaced Dhar; student demonstrators were first employed for a period of six hours per week, Miss G. E. Mocatta and G. A. V. Foster each being paid £10 per term to mark the intermediate exercise and practical books and to demonstrate in the laboratory to the students whose books they had marked. Under an arrangement between the College and the Department of Scientific and Industrial Research Astbury, Gibbs, Müller, W. G. Plummer and Shearer became Research Assistants for the 1922-23 session; Backhurst and Stiles having joined the National Physical Laboratory, S. Northeast, B.Sc., R. C. Richards, M.Sc., B.A., were appointed Assistants and J. R. H. Coutts, B.Sc., and J. J. Hedges, B.Sc., both ex-students, were appointed Demonstrators, although Hedges left at December for a research post at Woolwich and Coutts went to Rothamstead at the end of the session, later becoming Professor of Physics in the University of Grahamstown, South Africa.

After the war the Mechanics course was taken over by the Mathematics Department, and after the 1920-21 session considerable alterations were made to the lecture programme, the arrangements for the two sessions from 1921 to 1923 being as follows:-

X - Matriculation class, 4 lectures per week throughout the session, given by Gibbs;
Y - Intermediate class, divided into three groups, 3 lectures per week throughout the session,
Y1- Mathematical group taken by Porter,
Y2- Biological and Medical group taken by Sutherland,
Y3- Engineering group taken by Wood;

First-year lectures for students having passed, or having been exempted from, the intermediate examination:
Z1 - General Electric Theory, one per week during the first and second terms, given by Bragg;
Z2 - Thermodynamics, two per week in the first term, given by Porter;
Z3 - Properties of Matter, two per week in the second term, given by Wood;
Z4 - Electrolysis and the Theory of Solutions, one per week in the third term, given by Porter;
Z5 - Geometrical Optics, two per week in the third term, given by Wood.

Second-year lectures:
Z6 - Physical Optics, one per week in the first and second terms, given by Wood;
Z7 - Sound, one per week in the first term, given by Wood;
Z8 - Heat, two per week in the second term, given by Porter;
Z9 - Theory of Electrical Measurements, one per week in the second and third terms, given by Wood;
Z10 - Electron Theory, two per week in the third term, given by Bragg.

The course of instruction in practical physics in the laboratory was designated Z11; students taking physics as a subsidiary subject were required to attend the laboratory one day per week, while those taking it for the pass/honours degree course were required to attend two/three days per week respectively.
The A1 or Higher Senior Lectures, four per week over the two-year period, were shared by Bragg and Porter.
The course on Thermodynamics for second-year engineers, designated Z12, one lecture per week in the second and third terms, was given by Wood.

There were three postgraduate courses:-
A2 - Radioactivity, Radiation and X-rays, one lecture per week, given by Bragg;
A3 - Electric Oscillations and Waves, one lecture per week in the first term, given by Porter;
A4 - Thermodynamics, one lecture per week, given by Porter.

With the exception of Wood, who ran the undergraduate laboratories and dealt with such administrative work of the department as was delegated by Bragg, members of staff undertook research. It should be realised that until 1915 the only higher degree awarded by the University of London was the D.Sc. gained in general by some good independent research over a ten-year or more period. The Ph.D. degree was then usually obtained by postgraduate study at a German university. In 1915 the University introduced the M.Sc. degree awarded after one year or two years of postgraduate study or research, and in 1920 the Ph.D. degree was introduced requiring a minimum of two years research. As pointed out by Wood this doctorate soon became a necessary qualification for advancement of academic staff and a valuable asset for entry into industry. It led to a considerable increase in the number of postgraduate students, but also to a marked decline in the standard of teaching and especially demonstrating in the undergraduate laboratories by junior staff keen to obtain promotion (W.61). Astbury determined the crystal structure of tartaric acid; Backhurst studied the variation of the intensity of reflected X-radiation with crystal temperature; Clark published a paper on the average range of beta-particles in different materials; Gibbs published papers with Porter on systems with propagated coupling and the theory of freezing mixtures; Shearer published a paper on the relation between molecular and crystal structure as shown by X-ray crystal analysis; Sutherland worked on architectural acoustics, publishing a paper on the whispering gallery phenomenon in St. Paul's Cathedral, and was responsible for the acoustical properties of the hall in Friend's House, Euston Road; and Porter continued with his miscellaneous researches.

Alfred William Porter, D.Sc., F.R.S., succeeded Bragg as University Professor as from 1 October 1923, the Quain Chair being in abeyance. He was born in Liverpool on 12 November 1863 and began training as an architect, but his interest in physics having been stimulated by Oliver Lodge, he started to study the subject seriously round about the age of twenty five. A student first at Liverpool University College, he graduated with first-class honours under Carey Foster in 1890, becoming successively Demonstrator in 1891, Assistant Professor in 1896, Fellow of the College in 1897, and University Reader in Thermodynamics in 1912. In 1911 he was elected to the Fellowship of the Royal Society. From 1906 to 1912 he was Recorder of Section A of the British Association, and in 1914 he deputised for Trouton as President of this Section in Australia; on this occasion the University of Melbourne conferred on him the honorary degree of D.Sc. Later he became President of the Section in Glasgow in 1928. In 1913-14 he was President of the Röntgen Society and later became an Honorary Member of the Society under its changed name of the Institute of Radiology. From 1920-22 he was President of the Faraday Society. As stated earlier he had been in charge of the department from the resignation of Trouton to the appointment of Bragg, and during Bragg's absence on war service. The decision not to fill the Quain Chair was made possibly owing to the nature of his researches being outside the main fields of physics in vogue; however once the decision was taken to make him Head of Department, the refusal to grant him the Quain title was unkind and unworthy of the College considering his long distinguished service and his age of sixty, leaving only five years before retirement.

In the 1923-24 session W. W. Barkas, B.Sc., and E. G. Richardson, M.Sc., were appointed as Demonstrators, and E. Tyler, M.Sc., as an Assistant; Professor W. W. Wilson was brought in from Bedford College as Quain Lecturer, in accordance with the terms of the Quain Trust, to assist Porter with the Higher Senior Classes. Sutherland, now a Senior Lecturer, left at the end of the session to become Principal of Dalton Hall, University of Manchester. Richards was made Quain Lecturer in Physics in the following session; Smith was made an Assistant Lecturer and L. F. Bates, B.Sc., Ph.D., from Bristol University, joined the staff in the same grade. Northeast was not re-appointed for the 1925-26 session, but A. C. Burton, B.Sc., a College graduate, was appointed as Demonstrator only to leave at the end of the session for the post of Physics Master at the Liverpool Collegiate School, and later becoming Professor of Biophysics at Western University, Ontario, Canada. Smith and Tyler also resigned, the former on his appointment as Professor of Physics at the School of Engineering, Cairo and the latter to become Lecturer at the College of Technology, Leicester. Following these three resignations, G. B. Brown, M.Sc., who had been a Research Assistant of W. L. Bragg at Manchester, joined the staff as an Assistant, R. C. Brown, B.Sc., a graduate from Queen Mary College, as Demonstrator, and A. M. Cassie, M.A., B.Sc., as Assistant Lecturer for the start of the 1926-27 session. At the end of this session Richards left for the R.A.F., Cranwell, and Gibbs returned from the Royal Institution, where he had become an authority on the structure of quartz, as a Research Assistant for the next session.

In the 1924-25 session the Y1, Y2 and Y3 Intermediate courses were taken by Wood, Smith and Bates respectively. Richards took over the Z1 course, Porter took the Z2, Z4, Z8 courses and a new Z7 course on Electron Theory, the lectures on Sound being transferred to Z3, taken by Wood, as were Z5, Z6 and Z9; the Physical Laboratory course was re-designated Z10. There were three postgraduate courses, A2 Modern Problems in Diffraction with special reference to X-rays, A3 Crystal Structure and X-rays, and A4 Modern Developments in Thermodynamics, A2 and A4 being taken by Porter, and A3 by Smith. In the following session there was added A5 Quantum Theory by Richards, but it was replaced by a new A4 Vacuum Techniques, Developments in Quantum Theory, Investigations in Turbulent Motion in the next session. In Porter's last session the Z courses were listed in the Calendar as First Year, Z1 Heat and Thermodynamics, Porter; Z2 Electricity and Magnetism, Bates; Z3 Properties of Matter, Wood: Second Year, Z4 Electricity and Magnetism, Bates; Z5 Sound, Wood; Z6 Light, Wood. A4 became Recent Experimental Work in Sound by Richardson.

During Porter's headship members of staff with the exception of Wood combined teaching with research. Bates worked on the range of alpha-rays in rare gases, and the specific heats of ferromagnetic substances; Barkas and Coutts studied the distribution of particles in colloidal suspensions; Cassie published a paper on secondary and tertiary beta-rays with Professor H. Robinson; Richards published papers on the resistance of a hot wire in an alternating air current, a method of studying the behaviour of X-ray tubes, and a note on high-frequency oscillating discharge in rare gases; Richardson published on Lissajou's whistling flame, aeolian tones, theories of the singing flame and the Trevelyan rocker, critical velocity of flow past objects of aerofoil section, novel experiments in aerodynamics, amplitude of sound waves in pipes, building acoustics, and characteristic curves of liquid jets (with Tyler); Smith published on the calculation of the magneton number of an atom in solution, abnormal reflexions of X-rays, molecular symmetry in crystal structure, and theories of magnetism; both Richardson and Smith wrote textbooks, the former on 'Sound; a Physical Text-book' (Arnold & Co., 1927) and the latter on 'Vacuum Practice', a translation of 'La Technique du Vide' by L. Dunoyer (G. Bell & Sons, 1926). Porter continued with his miscellaneous researches publishing some fifteen papers alone as well as those with his collaborators, including research students; the former covered such topics as eddies in air, heat engines and refrigerating machines, single crystals of aluminium and other metals, the law of molecular forces, a revised equation of state, the vapour pressure of binary mixtures, X-ray spectra formed by diffraction gratings, and the Soret effect. When Porter retired the Eagle mounting of a six-inch Rowland grating, which was housed in the central room of the ground floor of the Carey Foster laboratory, was transferred to the University Observatory at Mill Hill. C. C. L. Gregory, the assistant lecturer in Applied Mathematics, who was responsible, under Professor Filon for all the work in astronomy, had supervised the construction of the mounting in the departmental workshop and continued to have charge of it.

Rankine in his Royal Society Obituary Notice after citing Porter's service under the four Professors - Carey Foster, Callendar, Trouton and Bragg - writes "It was not until 1923 that he himself became Professor in the Department to which he had devoted so much of his energy. There is little doubt that he could have secured more rapid advancement, but for his apparent reluctance to leave London, and the restriction of opportunity thereby imposed. He preferred to remain as the backbone of the teaching organization, and those who studied physics at University College during the period from 1900 to 1923 are indebted to him for most of what they learnt. Porter was, primarily, a teacher, and an excellent one, especially to senior students. His original contributions to knowledge were numerous and notable, but they seemed to emerge chiefly from his studies of subjects upon which it became necessary for him to give lectures. He would find the theory of such a subject in what he considered to be an unsatisfactory state, and proceed to reformulate it with precision. His publications on the theory of osmotic pressure are a case in point. His interests ranged over most branches of physics, but he will be remembered chiefly as a reliable and original investigator and exponent of thermodynamics".

Porter wrote an excellent textbook on 'Mechanics' (Murray 1905) which the publishers unfortunately let go out of print; as mentioned earlier he collaborated with Carey Foster on the latter's adaptation of Joubert's 'Electricity and Magnetism'; he was responsible for the fifth edition of Preston's 'Light' (1928); and he wrote 'Thermodynamics' (1931) and 'The Method of Dimensions' (1933) in the series of Methuen's Monographs on Physical Subjects. He was a kindly, gentle man; although a bachelor living with a sister, he was very fond of children, and delighted in giving them a treat at the pantomime, which he enjoyed regularly for many years. He was reticent about himself and his family, being known to his colleagues only in his professional capacity. His chief recreations were walking and cycling; he travelled by aeroplane in its early days. Every day he lunched at Maple's with a few friends, continuing to do so after retirement. It was near Maple's that he was seriously injured in a street accident early in 1938; after a partial recovery he went to live with his sister in West Kirby, Cheshire, where he died on 11 January 1939.

When Porter retired in 1928 he was succeeded by another old student of the department, E. N. da C. Andrade, D.Sc., Ph.D., who left the Professorship of Physics at the Artillery College, Woolwich to occupy the Quain Chair. Andrade was born on 27 December 1887, the second son of Henry da Costa Andrade, the Andrade family having left Portugal for England during the Napoleonic era. In 1897 he went to St. Dunstan's College, Catford, one of the first schools in the country to have a science laboratory and to introduce practical work into the curriculum. A bright and industrious pupil, interested in both literature and science, he entered Trouton's department with a scholarship in 1905, gaining first-class honours in 1907. As an undergraduate he was welter-weight boxing champion of the College and also a member of the first-eleven cricket team; there is a Union photograph (H & N, 219; 129) showing him a member of the 1906 team. Turning his attention to research as the first holder of the Trouton Scholarship, he worked on the viscous flow of lead, fuse wire (an alloy of lead and tin), and copper at constant stress, achieved by means of a buoyant hyperbolic weight. He found that after an immediate extension, the flow can be divided into transient and viscous components, the former being proportional to the cube root of the time of loading and the latter being constant throughout the period of loading. It will be recalled that Trouton and Rankine had worked on the stretching and torsion of a lead wire beyond the elastic limit, and from Andrade's acknowledgement in his paper (Proc. Roy. Soc. A, 85, 1) it is clear that the suggestion and inspiration for the work derived from Trouton. The use of constant stress, rather than constant load as was then the practice in engineering creep tests, was decisive in distinguishing the transient flow, which largely determines the early part of the creep curve, and the viscous or constant flow, now generally referred to as "steady-state creep". Turning his attention to mathematics, Andrade gained the Jessel Studentship and the Ellen Watson Scholarship and at Karl Pearson's suggestion he worked on the distribution of slide in a right six-face subject to pure shear. In 1910 he was awarded an 1851 Exhibition Scholarship (1910-13) and at Trouton's suggestion he went to Heidelberg to work under Lenard on the electrical properties of flames, gaining his Ph.D. degree, summa cum laude, a distinction then usually reserved for German students, in November 1911.

'A physics research student at Heidelberg in the old days' (Physics Education, 1, 69) gives a fascinating account of his time under Lenard and his immediate supervisor, Ramsauer. Returning to England, he went to the Cavendish Laboratory, but after a few months of unproductive work he left Cambridge for Gower Street to resume work on the flow of metals, including iron and solid mercury, under constant stress covering a wide range of stresses and temperatures. He demonstrated that the transient and viscous flows could be obtained generally if the experiments were performed at high stresses and appropriate temperatures relative to the absolute melting point; for example, iron at 717 K behaved like lead at room temperature, and lead at 93 K behaved like copper at room temperature. He also made observations of the regular surface markings on circular wires of mercury, stretched plastically at 195 K, giving an accurate description and interpretation of this mode of tensile deformation of a single crystal by glide on slip bands some ten years before research on metal single crystals generally began. In 1913 he went to Manchester as a John Harling Fellow to work with Rutherford and they made the first determination of the wavelengths of gamma rays from radium by means of the crystal method. Cottrell in his Royal Society Biographical Memoir records that it was at Manchester that Andrade first acquired the name of Percy, apparently because someone said he was the least Percy-like man they knew! He liked the name, used it freely himself, and was widely known by it in the scientific world, although he was always Ted to the family.

At the outbreak of war in 1914 Andrade was commissioned as an artillery officer, and served on the French front from 1915 to 1917, first with a battery of 60-pounders and later with a group of counter-batteries on the Arras salient, where with Lawrence Bragg and others the exact position of the enemy's guns was tracked down with ingenious apparatus. Andrade rose to the rank of captain, and was mentioned in dispatches; he was injured when a shell burst prematurely in a battery gun, and later when a sudden burst of gunfire caused a horse to shy and roll on him. In 1917 he returned to England to work for the Ministry of Munitions on explosives.

At the end of the war Andrade was awarded the D.Sc. degree of London University, and in 1920 he was appointed Professor of Physics at the Artillery College, Woolwich on Rutherford's recommendation. Having no opportunity to resume research in nuclear physics, he turned his attention to the flow of liquids, particularly the phenomenon of viscosity which continued to occupy his mind for many years. With J. W. Lewis he exhibited by means of colloidal silver particles the types of motion of a viscous liquid between two rotating concentric cylinders. They also demonstrated Ostwald's "structural turbulence" for an ammonium oleate sol. However his association with Rutherford led him to write The Structure of the Atom, which was first published on 5 July 1923 and ran into several editions, one of the features of the book being the dedication to Rutherford. Sir Neville Mott in his article on Niels Bohr (Phys. Bull., Vol.36, No.4, 1985) writes "At school I knew about Bohr's theory, and when I went to Cambridge with the intention of studying quantum theory, the orbits were almost an article of faith. Andrade's book, with the orbits profusely illustrated, was almost a bible, as was Sommerfeld's Atomic Theory and Spectral Lines." He reproduces the diagram of the orbits of Radium (88) from Andrade's book at the head of the article. Cottrell (loc. cit.) records that at this time he was involved with E. V. Appleton in studying various suggestions that were still coming into Government circles in the aftermath of the war. Amongst them was a proposal for making gold from base metals and this inspired Andrade's friend, Hilaire Belloc, to write the novel, The man who made gold, which he dedicated to 'Professor Andrade, the man who taught me how to make gold'.

Back in College

Elected a Fellow of the College in 1916, Andrade returned as Quain Professor of Physics at a salary of £1000 per annum from 1 August 1928 for his first period of seven years, Rutherford again being his supporter. He brought with him Leonard Walden, who was appointed Chief Laboratory Assistant at £4:10s per week; Walden had joined Andrade shortly after his appointment to the Artillery College Chair; he had a great knowledge of laboratory arts and was very skilful in their application. In the late thirties he published papers on instrument suspensions; laboratory cements and waxes; and the design and construction of small electrical laboratory furnaces. Andrade continued to occupy the Chair until January 1950 when he resigned on being appointed Director in the Royal Institution, Resident Professor and Director of the Davy Faraday Laboratory. He established a strong research school, the main fields being acoustics, the viscosity of liquids, and the physics of metals, particularly creep and single crystals.

Acoustics

In 1929 with S. K. Lewer he announced in Nature new phenomena in a sounding dust tube, particularly the antinodal discs. After studying the method of formation of sand figures on a vibrating plate, D.H.Smith and Andrade measured the antinodal disc separation to determine the velocity of sound in air and argon over a wide audio-frequency range; a well-marked variation of velocity with frequency over the range 600 - 1200 c/s proved to be some feature of the method as generally applied. Following this variation F. A. Walch at Andrade's suggestion explored the constancy of the velocity of sound by comparison of the wave-form of a complex sound at different distances from the source over the frequency range 250-1000 c/s; constancy within 1 in 500 for the lower frequencies and within 1 in 1000 for the higher frequencies was established. The last determination of the velocity of sound in air at sonic frequencies was made by R. A. Scott for his Ph. D. degree awarded in 1938. He applied the method based on the reaction of a closed resonant tube on an electromagnetically driven diaphragm, suggested by Andrade and investigated previously by T. A. Eames and then by D. H. Smith. Using tubes of diameters 3.94 and 8.00 cm and a frequency range from 800-1500 c/s the velocity in free air was calculated. E. B. Pearson, an old student, who became an Assistant Lecturer in 1931, investigated the velocity of sound in air at supersonic frequencies; using cigarette smoke particles to form figures at the nodes in a resonance tube to determine the wavelength, the velocity was calculated from the known frequency of the piezo-electric crystal used to maintain the oscillation. The results showed a definite dispersion in the frequency range 92.2 - 801.6 kc/s. However in view of the ensuing criticism, R. C. Parker using magnesium oxide smoke particles and eliminating various possible sources of error, determined the velocity in air, oxygen and nitrogen and found no evidence of dispersion in the aforesaid frequency range. Andrade and Parker devised a pipe maintained by a loud-speaker unit at one end, while the other end was open to the atmosphere, as a standard source suitable for making measurements of audibility. The intensity of the source was derived from observations of the amplitude of magnesium smoke particles held in suspension in the glass tube forming the pipe. Determinations of the thresholds of audibility were made at frequencies of 410 and 646 c/s from the averages of the observations of five auditors. Andrade published the results of his investigation into the phenomena in a sounding tube excited by a valve-maintained diaphragm in Phil. Trans. A, Vol.230, 1932. Using fine smoke particles he was able to measure the amplitude of the vibrations in the tube and establish the existence of the circulation predicted by Rayleigh. Around larger particles vortex systems were formed, and from observations of these considerable light was thrown on hydrodynamical problems. The paper included beautiful photographs of antinodal discs, the circulations, and the vortex systems.

At the suggestion of Andrade, G. B. Brown took up the work on sensitive flames, making an extensive study enriched with some beautiful photographs; he also made a most comprehensive investigation of edge tones, followed by a theoretical discussion. Andrade had also worked on sensitive flames, and in 1937, with L. C. Tsien, examined the velocity distribution of a liquid-into-liquid jet, returning to the subject just before the outbreak of war. In 1941 he was invited to deliver the 25th Guthrie lecture and chose as his subject a problem of Guthrie's time, namely The Sensitive Flame; this was a comprehensive review of work in the field, including his own contributions on flames and liquid jets, especially his latest work on the development of the instability of a plane jet worked out by means of the hydro-magnetic analogy.

Viscosity

To account for the pronounced decrease of the viscosity of liquids with rise of temperature, Andrade in 1930 put forward the simple expression, h = B exp(b/T), to represent the variation of viscosity with temperature at constant pressure; it was derived on the supposition that the average distance of the molecules is unaffected by the temperature. He realized subsequently that the expression had already been suggested by de Guzman in 1913. In 1934 he modified it to hv = C exp(c/vT) to take account of the effect of expansion on the average molecular distance, and on the potential energy, v being the specific volume. Both expressions gave close representations of the variation of viscosity with temperature. The mechanism responsible for the viscosity of liquids was regarded as fundamentally different from that in gases, and the problem was approached mainly from the point of view of the solid state. A liquid was considered to consist of molecules vibrating under the influence of local forces about equilibrium positions slowly displaced with time. At extreme libration a molecule of one layer may momentarily combine with one of an adjacent parallel layer, supposed to be moving past it with a drift velocity given by the bulk velocity gradient, the combination being of extremely short duration but sufficing to ensure a sharing of momentum parallel to the drift, Andrade likening it to "a shaking of hands". Taking the frequency of vibration of the liquid molecules at the melting point to be the same as that for the solid at the same temperature, he obtained a formula for the viscosity of a monomolecular liquid at the melting point, which closely fitted the observed values for several metals and for liquid helium I, spanning a 1000-fold range of viscosities.

After developing an accurate viscometer for volatile and hygroscopic liquids with K. E. Spells, Andrade turned to the oscillating-sphere method and, with Y. S. Chiong, determined the viscosity of water over a wide range of temperature. The apparatus was then modified with L. Rotherham to eliminate the damping of the oscillations; this was achieved by attaching a small permanent magnet to the sphere, which was positioned at the centre of a pair of Helmholtz coils, and discharging a condenser through the coils once in every complete swing to supply the energy dissipated by the viscous forces. They determined the viscosity of hexane in terms of that of water. There followed the determinations of the viscosities of liquid sodium and potassium by Chiong, and liquid gallium by Spells over an extended range of temperature. F. H. C. Crick (later of D.N.A. fame) had his work on the viscosity of water at high pressures cut short by the outbreak of the war. E. R. Dobbs, who graduated during the war, returned thereafter to determine the viscosities of liquid lithium, rubidium and caesium thereby completing the extensive study of the liquid alkali metals, which proved the superiority of the modified formula taking into account the molecular volume.

In another series of experiments Andrade, with C. Dodd, both before and after the war, studied the influence of electric fields on the viscosity of liquids. They soon established that the effect was only shown by polar liquids, being due almost entirely to an accumulation of ions in the neighbourhood of the electrodes between which the liquid flowed, thereby narrowing the channel and seeming to increase the viscosity. By the use of high-frequency alternating fields and the careful control of the experimental conditions, they proved the existence of a small effect with polar liquids, the fractional increase of viscosity being proportional to the square of the electric field transverse to the direction of the flow. After the war Andrade returned to the study with J. Hart and they showed that the effect varies with the frequency, increasing from a finite value at zero frequency according to a simple parabolic law.

Physics of Metals

Andrade returned to the study of creep in 1929, working with B. Chalmers. They replaced the buoyant hyperbolic weight with a simple beam device for maintaining constant stress, and measured electrical resistivity to detect the changes in the physical structure of the material which was responsible for the creep behaviour. These experiments and those by Gibbs and N. Ram Lal using X-rays showed that, when a polycrystalline wire of cadmium or of tin is extended, a rotation of the axes of the crystallites takes place. In the thirties various experiments on creep behaviour were included in the single crystal programme, e.g., the demonstration of transient flow in cadmium crystals following the initial extension. However this flow did not follow the "cube-root of the time" law presumably owing to the tensile stress rather than the resolved shear stress being kept constant. Later, when the Andrade-Chalmers beam was modified by other workers to give constant shear stress on the glide planes, was the law confirmed for single crystals.

After the war, Andrade became increasingly interested in the influence of the surface condition of a metal on its creep behaviour. At first he bombarded single crystals of cadmium with alpha particles, but later, following the development of an automatic recording apparatus for the study of flow and recovery of metals with A. J. Kennedy, consistent evidence began to be obtained from polycrystalline wires that the crystal grains in the surface of the material strongly influenced the overall deformation of the specimen. Kennedy also devised a method for fitting the Andrade creep equation to experimental results, and studied the effect of instantaneous prestrain on the character of creep in polycrystalline lead. Finally Andrade replaced tensile stress by simple shear to keep the surface area and cross-section constant during deformation, and to enable the sense of the applied stress to be reversed at will. In a series of experiments, begun at College with K. H. Jolliffe, applying this technique to lead, they showed that a deformation strictly proportional to the square root of the time takes place at small strains before the cube root regime sets in; and at large shear strains, a steady-state flow is obtained at a rate which is the same for forward and backward stress. In contrast at lower strains, before the the initial grain structure of the metal is thoroughly broken up, the forward and backward behaviours are quite different. Continuing these researches at Imperial College, with D. A. Aboav it was shown that the hexagonal metal cadmium behaved differently from lead in a manner explicable in terms of the crystal structure. Also with V. M. Morton an investigation of the angular distribution of the slip lines on the surface of sheared lead, showed by an analysis of resolved shear stresses, crystal symmetry, and statistics of potential slip lines orientations that the distribution observed at low stresses could be accounted for quantitatively on the basis that there is time during the flow at these small stresses for thermal agitation to diminish the interactions of neighbouring crystal grains. Cottrell (loc. cit.) writes "These final researches of Andrade's have uncovered a rich variety of behaviour and revealed the true complexity of the creep process. It is too early to expect to understand all the things that happen in this complicated story; but at least the main characters - the migration and sliding of grain boundaries, recrystallization, the pattern of slip bands, geometric freedom of surface grains, interaction of twins and slip bands - have been clearly identified by Andrade, who has also given us the simplest and most systematic experimental techniques for displaying and disentangling them".

The single-crystal work was resumed early in the thirties, with studies involving single crystals of cadmium, lead, and bismuth, prepared by the use of a narrow furnace travelling along the wires. Two of the first publications were on the determination of the crystal axes of single crystal wires; B. Chalmers' geometrical method, almost as long as the X-ray method, presumably stimulated Roscoe and Hutchings to devise their rapid method for certain metals, particularly wires of the hexagonal metals. Roscoe made a remarkable observation on the effect of the surface in cadmium crystals, namely, with a superficial layer of oxide one or two molecules thick, the critical shear stress may be as high as twice the value obtained with a clean surface. Andrade developed a method of preparing single crystal wires of metals of high melting-point; the wire was heated by the passage of an electric current, a local temperature gradient slowly travelling down the wire, this being obtained by means of a subsidiary furnace surrounding the wire. L. C. Tsien and Miss Y. S. Chow, and Andrade and Miss Chow applied the method to prepare single crystals of molybdenum and alpha-iron respectively. In 1937 Andrade and Roscoe published their paper on glide in single-crystal wires of cadmium and lead; the effects of rate of glide and of impurities on the measured critical shear stress of cadmium were investigated, and the hardening and recovery of cadmium and the spacing of the glide planes in lead were shown to be independent of a range of factors and so to have a physical significance. Andrade and his collaborators undertook a series of experiments to establish, more precisely than before, the glide elements of body-centred cubic crystals. In 1937 his paper with Tsien pointed out the particular interest of b.c.c. crystals, and recorded their determinations of the glide elements for single crystals of sodium and potassium at atmospheric temperatures, viz. glide plane (123) and glide direction [111]. Another paper by Tsien and Chow described the glide elements for molybdenum, for which the glide direction was again [111], but the glide plane was different at different temperatures, viz. (110) at 1000 C and (112) at 300 and 20 C. Andrade and Chow also determined the glide plane of sodium as (110) at -80 C and (112) at -185 C. Andrade showed that the glide planes of b.c.c. metals changed from (112) through (110) to (123) as the ratio of the absolute temperature of the experiment to the absolute melting point increased from 0.08 for tungsten to 0.87 for potassium, the glide direction always being [111]. The case of iron was peculiar, in that all three planes had been suggested by different authors as operative at room temperature; the outbreak of war interrupted his investigations on this point before any conclusive results were obtained. The glide direction appears to be fundamental, this being in all cubic and hexagonal crystals the most closely packed line. The choice of glide plane appears to be influenced not only by temperature but by slight deformation, as shown by Greenland (see below). Andrade returned to the study of single crystals of mercury with P.J.Hutchings, publishing their investigation of the mechanical properties in 1935; then K.M.Greenland in 1937 published his study of the slip bands on single crystals of mercury at - 60 C, showing that with the purest mercury, regular or irregular slip surfaces could be produced at will - any slight preliminary bending of the crystal wire leading to perfectly plane surfaces, whereas absolutely unstrained wires gave irregular surfaces. He also determined the critical shear stress at - 60 C to be 7.0 gm wt/sq mm, and found it to increase progressively with small additions of silver up to 28 gm wt/sq mm at silver concentrations of 1:1000; by extrapolation he deduced a value not greater than 5.0 gm wt/sq mm at absolute purity.

Early in 1940 Andrade summarized the marked contrast between the behaviour of single crystals under stress at high and low temperatures as follows:-
Low (High) Temperature
Great (Small) hardening with glide
Close (Widely-spaced) glide planes
Large (Small) crystallite rotation
Large (Small) hardening
Little (Large) time flow

Furthermore the effect of temperature on hardening, as measured roughly by the spacing of the stress-glide curves for a given difference of temperature, is comparatively small at high and low temperatures, but greater at intermediate temperatures. (Andrade & Chow, Proc. Roy. Soc. A, 175, 290).

After the war, with R. F. Y. Randall and M. J. Makin, Andrade made a series of experiments on the effects of surface condition on the plastic yield strength of cadmium and zinc crystals, which led to the general conclusion that the films of oxide or hydroxide, normally present on these metals, increase this strength; consequently the contact of liquids which affect these films produces corresponding changes in the rate of plastic flow under a given stress. Much of this work was done with various electrolytic solutions, but following some interesting observations by the Russian physicist, Rehbinder, attention was directed to the effects of immersing the stressed crystals in solutions of oleic acid in paraffin. It was shown that the increase in plastic flow caused by the surface-active liquid occurred only after a time delay of several minutes and was almost certainly 'due to a disintegrating action of the agent on the oxide film, which in its original condition strengthens the crystal ...'

With C. Henderson a new method was developed of growing single crystals of metals of higher melting point, and careful studies were made of the stress-strain curves obtained by stretching pure and clean crystals of silver and gold. Until this work it had been supposed that such curves, even when expressed in terms of shear stress and shear strain on the most highly stressed family of slip planes, were characteristically parabolic, with the greatest rate of strain hardening occurring at the start of plastic deformation. Andrade and Henderson made the important discovery that, when care is taken to avoid adventitious 'turbulence' in the plastic flow, the initial behaviour is quite different, viz. the plastic part of the stress-strain curve begins with a linear region, which they termed 'easy glide', where the coefficient of strain hardening is very small or even zero; and then, after a glide of several percent, there follows a steeply rising part, of rounded form, broadly similar to the more familiar parabolic curves. (Andrade & Henderson, Phil. Trans. R. Soc. Lond. A, 244, 177). This discovery was later confirmed at the Royal Institution with Aboav when copper crystals were studied in various orientations and over a range of temperatures. Cottrell (loc, cit.) states "This discovery...has played a key part in the development of the theory of strain hardening, steering this theory away from its early form, in which it tried to account for the effects in terms of interactions of dislocations gliding in parallel slip lanes, to its modern form, in which the main effects are due to the mutual interference of dislocations in intersecting slip planes".

Other researchers

In 1934 Andrade published a short paper in Nature with J. G. Martindale showing that thin sputtered films of gold and silver on glass and natural faces of diamond crystallized into small spherulites, each about one micron across, when heated, and that the spherulites formed patterns which could be reproduced precisely, irrespective of the rigour of cleaning the surface. As their 1936 paper on 'The Structure and Physical Properties of Thin Films of Metals on Solid Surfaces' (Phil. Trans. R. Soc. Lond. A, 234, 69) pointed out, they were revealing for the first time the submicroscopic surface cracks which, as conjectured by A. A. Griffith, were responsible for the low breaking strengths of brittle materials. Andrade and Tsien then showed that the lines could also be developed consistently on glass by sodium vapour etching the material preferentially along them; various subsidiary experiments including the creation of such lines in the vicinity of diamond scratches on previously featureless regions of the surface, left little doubt that the lines were traces of Griffith cracks on the surface. Amongst his later work, there was that on grain growth in metals of close-packed structure with Aboav.

Members of staff carried on with their own research, Bates continuing to study the properties of ferromagnetics with low Curie points, particularly manganese arsenide. He devised an electrical method for measuring the specific heats of such substances in powdered form, and applied it to investigate the variation of the specific heat of manganese arsenide in the neighbourhood of its ferromagnetic critical point. He also studied the magnetic and thermo-electric properties, and the resistance of short rods of manganese arsenide. With D. V. Reddi Pantulu he described the preparation in vacuo of pure amorphous manganese, which was found to be paramagnetic without trace of ferromagnetism, and to obey the Curie-Weiss law over the temperature range 90 to 600 K. Then Gibbs joined them in a further study of the magnetic properties of the substance.

Bates also devised apparatus to measure the hysteresis curve of a ferromagnetic rod; made a suitable adaptation for teaching laboratories of Schuster and F. E. Smith's method of measuring the horizontal component of the earth's magnetic field; and devised a null method for the measurement of the horizontal and vertical components of the earth's field. With B. J. Lloyd-Evans of the Department of Mechanical Engineering he produced an electromagnet suitable for many branches of research, special attention being paid to the oil-cooled coils to enable currents up to 20 A to flow for considerable periods; the performance of the electromagnet was investigated by means of a small magnetic potentiometer. At the suggestion of Wood, who was Joint Editor of Science Progress, Bates contributed the Advances in Physics pieces for the journal. The title of Reader was conferred upon him in 1930, and in 1936 he was made Lancashire-Spencer Professor of Physics at University College, Nottingham, where he established an active and thriving research school which won an international reputation in the field of magnetism. Bates was elected to the Fellowship of the Royal Society, created a C.B.E., became Vice-Principal of the University College before it received its Royal Charter, and Deputy Vice-Chancellor thereafter. In 1961 there appeared a fourth edition of his book on 'Modern Magnetism', first published in 1939. Richardson continued his work on fluid flow and on architectural acoustics; he also published papers on the acoustics of orchestral instruments and of the organ, the dynamical theory of the ear, jet propulsion of aircraft, and the rocket as a means of propulsion. After going to Armstrong College, Newcastle-on-Tyne, he was made an Honorary Lecturer in Acoustics in the Department of Architecture, and returned each year to give a course of lectures on architectural acoustics.

Gibbs having gained his D.Sc. in 1927, was made a Lecturer in 1931. Then, with Indian research students V. N. Thatte and N. Ram Lal, he worked on the temperature variation of the frequency of piezoelectric oscillations of quartz, and on crystallite orientation in a polycrystalline metal during plastic flow respectively; and with Tsien on the production of piezoelectricity by torsion. In 1936 the University Readership vacated by Bates was conferred upon him.

R. C. Brown, who was made a Lecturer in 1930, worked on experimental methods of measuring surface tension, e.g., Jaegar's method applied to mercury; the ripple method, including the use of ripples as a diffraction grating, and the measurement of the amplitude and damping of ripples; and the determination of the surface tension of aqueous solutions of p-toluidine, and of mixtures of n-propyl alcohol and benzene. G. B. Brown, promoted to a Lectureship in 1931, worked on sensitive flames and edge tones as stated earlier, and published papers on the method and philosophy of science.

In 1931 Dr. F. C. Chalklin came from Sheffield University to fill one of the vacant lectureships arising from the resignations of Barkas, who went to the Forest Products Research Laboratory, subsequently gaining an international reputation there, and Cassie, who joined the Electrical Research Association. Chalklin specialised in the measurement of the wavelengths of soft X-rays, some measurements being in collaboration with his wife, Letitia. They developed a grazing-incidence plane grating, vacuum spectroscope and used it to measure wavelengths in the very soft X-ray region, e.g., the K-absorption edges of carbon, nitrogen, and oxygen, and the fine structure of carbon K-alpha. Other measurements made by Chalklin included the fine structure of the K-line of beryllium; electronic energy bands of solid copper, nickel, cobalt, and iron; the L spectra of iron, cobalt, nickel and copper; and, with S. P. Hillson, the L-alpha lines of some nickel alloys. He also developed, with S. S. Watts and S. P. Hillson, a 1m concave-grating vacuum spectroscope for wavelengths 15 to 1000 Å. In 1939 he was made a Reader for his contributions in the field of soft X-ray spectroscopy. At the end of the 1933-34 session both E. B. Pearson and N. L. Yates-Fish resigned as Assistant Lecturers and Drs. R. Roscoe and W. E. Duncanson were appointed to fill the vacancies. Duncanson published the first of his collaborative papers with C. A. Coulson, namely a comparative study of the wave-functions of the two simplest heteronuclear molecules, viz. the ground states of the single and double-electron ions formed by helium and hydrogen. Dr. T. B. Rymer, who was appointed to succeed Roscoe in 1935, left in December 1937 for a Lectureship at Reading University, and was replaced by Dr. C. Dodd. When Bates left at the end of the 1935-6 session, Dr. F. A. Vick from the University of Birmingham was appointed as an Assistant Lecturer, and in 1939 was one of the only two Assistant Lecturers to be promoted to Lecturer in the College. He took over the writing of the Recent Advances in Physics pieces for Science Progress. Dodd left College in 1939 for a Lectureship at St. Andrews.

Extra space for research

In Bragg's last session there were 13 postgraduate research students, including 5 Indians, and a few research assistants, paid by the College. The number in Andrade's time rose from 8 in 1928-9 to 12 in 1935-6 and fell back to 8 in the last session before the war; both Chinese and Indian students formed part of the complement of the Carey Foster laboratory; and incidentally Miss Patricia Koo, daughter of the Chinese Ambassador in London, was a member of the B.Sc. Special Degree class just before the war. Wood states that the number was largely governed by finance. In the middle twenties most postgraduates depended on their own resources, supplemented by fees from student demonstratorships and sometimes from teaching evening classes at London County Council Technical Institutes. Some of the better students, who took their final examinations at the end of their second year, spent their third year on research, and then obtained grants from the Department of Scientific and Industrial Research or their Local Education Authorities to enable them to complete their postgraduate courses. (W. 68). At the Assembly of Faculties on 5 July 1934 it was explained that the department's need for an entire new set of buildings, involving capital expenditure of some £75,000, was out of the question at that time, and all that was able to be done was to tackle the most urgent aspect, namely to provide some relief to the overcrowding of the Carey Foster laboratory. This had followed the purchase by the College in 1931 of the premises and land in Malet Place from Shoolbreds, the once-famous departmental store in Tottenham Court Road. After the proposal had been resisted to move the whole department to the old wharehouse, its southern part was converted into a laboratory, in which 100 Intermediate students working in pairs could be accommodated at the same time. The conversion was completed in 1934, and the number of Intermediate students doing their practical physics in the Foster Court laboratory rose from 173 in 1935-6 to 223 in 1937-8. The vacation of the Junior laboratory in the Main Building set free space to relieve the overcrowding of the research laboratory, students moving in after suitable adaptation of the old laboratory.

Dr. R. C. Brown in a note to the author writes "For two or three years before the outbreak of war in 1939 the new Junior Laboratory in Foster Court was used for practical physics examinations in the University of London Higher School (later to become Advanced Level) examinations. Hitherto these, and all other London practical physics examinations, had been held at Imperial College, but the burden became too much there when the number of Higher School candidates taking physics rose to more than 1000. R. C. Brown, assisted by W. E. Duncanson, was in charge of the operation, and Bert Stone led a team of the departmental technicians. As hitherto, the assistant examiners, each in charge of 10 or 12 candidates, were school and college physics teachers, who were members of the University's panel. The exercise was a good advertisement for U.C.L. as it was universally agreed that a new standard of efficiency had been set in the running of these examinations, both as regards the quality and reliability of the apparatus, and the data and other information supplied to the examiners."

Teaching

In his first session Andrade took over the Z1 course on Heat and Thermodynamics, gave some of the A course, and a postgraduate course on Modern Developments in Atomic Physics. Wood started his practice of giving three A lectures per week on Light and on Heat and Thermodynamics in alternate sessions. Richardson continued to give the postgraduate course on Recent Experimental Work in Sound. At its meeting on 5 November 1929, the Senate, after considering a report from the Board of Studies in Physics, recommended that the Principles, Methods and Theories of Physics should be treated mathematically and experimentally under the four main divisions:- Properties of Matter and Sound; Heat and Thermodynamics; Light and Radiation; Electricity and Magnetism. There followed the practice of U.C.L. students taking four common University papers, two alternative theory papers and two alternative six-hour practical examinations, set specially for them, at the B.Sc. Special Examination.

The Z-lecture programme was revised in the 1929-30 session to include an additional lecture per week in in both the first and second years. For the first year Z1 became Properties of Matter, R. C. Brown; Z2 continued as Electricity and Magnetism, Bates; Z3 became Heat, Andrade; and Z4 was introduced as Optics, Wood. In the second year Z5 became Optics, G. B. Brown; Z6 Electricity and Magnetism, Bates; Z7 Sound, Richardson; and Z8 was introduced as Heat, Wood. In the following session Z6 became Heat, Z7 Electricity, and Z8 Sound, both Andrade and Wood, and Wood and G. B. Brown interchanging years for the Heat and Optics lectures. This pattern continued up to the 1936-37 session with Gibbs taking over from G. B. Brown on Optics and from Richardson on Sound. In that session Modern Physics was introduced as Z8, given by Andrade, and this led to the temporary introduction of Z9 for Gibbs' sound lectures to the second-year students. For the first-year class, Properties of Matter was combined with Sound as Z1, still given by R. C. Brown. The departure of Bates led to G. B. Brown and Duncanson taking over Z2 and Z7 respectively, the only other changes being Chalklin taking over Z4 from Gibbs, and the omission of the then-redundant Z9. The only change of lecturers in the 1937-38 session, besides the customary alternation of Andrade and Wood with Z3 and Z6, was Chalklin for Gibbs on Z5. In the last session before the outbreak of war, Chalklin took over the Z2 course from G. B. Brown and the Z7 course from Duncanson, Dodd took over the Z3 course from Wood, and Gibbs resumed Z5, then designated Physical Optics, to complement Z4, Geometrical Optics.

Wood and Bates continued to take the Intermediate classes, Y1 Mathematical, and Y2 Biological respectively, and Barkas took over the Y3 Engineering Group. Richardson succeeded Bates in the 1929-30 session and when he left R. C. Brown took over Y2, Chalklin similarly taking over Y3 from Barkas. The only other pre-war change was in the 1938-39 session, Vick taking over Y3 from Chalklin.

The A-course lecturers are not recorded in the pre-war calendars, but the author in his first session, 1937-38, went to G. B. Brown's course, which followed closely Sir James Jeans' book on 'The Mathematical Theory of Electricity and Magnetism', and Gibbs' course on Geometrical and Physical Optics, both courses being given at the rate of three lectures per week throughout the session. In addition he attended Andrade's A-course on Hydrodynamics and Viscosity, his course Z3 on Heat and Thermodynamics, and R. C. Brown's course Z1 on Properties of Matter and Sound. He well remembers Andrade's introductory lecture including the importance of being able to write good English; examples being cited of the use of words, 'directing' rather than 'drawing' attention; 'applying' rather than 'using' a method; 'Dear Sir' followed by 'Yours faithfully', and 'Dear Mr. .....' followed by 'Yours sincerely' or 'Yours truly' according to the relationship. The suggestion to visit the Science Museum and to let him have a report of the visit was not taken up by anyone at the lecture!

The U.C.L. alternative papers V and VI each contained six questions, three of which were required to be answered in three hours. Typical questions set by Andrade were the first on paper V in the three years 1937-39, namely:-
Give an account of the mechanical properties of single crystals of metals.
Discuss the accurate measurement of liquid viscosity.
Write an essay on vortex motion in fluids.

Paper VI in 1937 contained two questions from him,viz.,
1. Explain what is meant by the method of dynamical similarity, and deduce a general expression for the resistance to motion of a body in a fluid, in terms of the velocity, acceleration and linear dimensions of the body, and the density and viscosity of the fluid. Adapt this expression to the case of the resistance to steady motion of a fluid through a pipe, and use this to discus the experimental results which have been obtained.
6. Discuss the general regularities of the optical spectra of elements with more than one optical electron and the way in which they have been interpreted by the aid of quantum numbers, illustrating your answer by considering the case of atoms with two optical electrons in somewhat more detail.

There was an innovation in the first six-hour practical examination in 1939, namely the introduction of only one experiment on the paper, as compared with the previous practice of three experiments, one being allocated to each candidate. The instructions ran as follows:-
Construct a parallel plate air condenser with the two glass plates and the tin foil provided, and use it to determine the capacity of an electroscope.
Use the electroscope to find the resistance per unit length of the thread supplied and verify your result by using two, or more, threads in parallel.
NOTES - (a) Determine the deflection of the leaf of the electroscope by projecting its image on squared paper.
Assume that the angular deflection is proportional to the difference of potential between the leaf and the case.
(b) A suitable electrometer will be available for calibrating the electroscope. Two points only should be determined.

Wood's position of being in charge of the undergraduate laboratories was formally recognized in 1931, the Council at its meeting on 30 June of that year recording the addition of Director of the Physical Laboratories to Andrade's title of Quain Professor of Physics, and the conferment of the title of Deputy Director on Wood. A short course in Workshop Practice under the direction of the Chief Mechanic, Mr. W. Fox, was announced in the 1931-32 calendar, at a fee of £1:11:6. The author recalls attending the course in 1937 and making a brass pencil/pen stand with an underlying drawer. E. J. Faulkner had succeeded Fox, who had retired at the age of 65 in 1937, but R. J. Fisher, who had joined the Workshop in 1923, one year before Fox, remained to provide the continuity of the course. The author also recalls the first critical marking of his practical book by Wood, whose written comment "Work fair", prompted him to seek an audience, from which he emerged suitably enlightened!

The War Years

The crisis of 1938 led to tentative arrangements being made for the evacuation of the College in the event of war. The Departments of Mathematics, Physics, Botany and Zoology, together with the intermediate and first-year medical students taking Chemistry, were to be evacuated to the University College of N. Wales in Bangor; the rest of the Chemistry Department, together with a member of the Physics staff to take charge of the subsidiary course in Physics, would go to the the University College in Aberysthwyth. The Bangor arrangements were confirmed at a meeting held in Bangor in April 1939. At the outbreak of war Andrade became Scientific Adviser to Dr. H. J. Gough, Director of Scientific Research, Ministry of Supply, having been a member of its Advisory Council on Scientific Research and Technical Development since its inception; incidentally one of the two Deputy Directors was Dr. E. T. Paris, an old student of the department in Trouton's time. Vick went with Andrade to occupy a room with Professor J. D. Cockcroft, who had been appointed an Assistant Director of Scientific Research, and Gibbs went to the Royal Aircraft Establishment at Farnborough. Miss E. Storey, the departmental secretary, accompanied Andrade and Vick to the Ministry. Dodd having gone to the University of St. Andrews, this left Wood, Duncanson and the two Browns, accompanied by E. C. Rowe and C. A. R. Tayler, the chief laboratory and lecture technicians respectively, to carry on the main work of the department in Bangor, and Chalklin to look after the chemistry students taking physics as their subsidiary subject in Aberystwyth.

In the early summer of 1939 when war seemed inevitable, Rowe began to assemble apparatus for removal to Bangor, and in July he and Tayler packed c.1.5 tons of apparatus in a steel container, which was transported to the railway sidings at Bangor by Pickfords. War was declared just as Rowe and his family were finishing their holiday in Yorkshire, and they went direct to Bangor. The container was transferred to ground adjacent to the Physics Department in Deiniol Road, and a few days later unpacked, the apparatus being stored in two large cupboards in the apparatus room next to the physics theatre.

Meanwhile Wood, who had succeeded Col. H. J. Harris as Sub-Dean of the Faculty of Science and Tutor to Science Students in 1933, had gone to Bangor with Miss W. Radley, Deputy Registrar, to cope with all the problems involved in the evacuation. They worked on a lecture bench in a small theatre in the main College building in Upper Bangor, using the student desks for sorting out the multitude of papers and letters requiring attention. Students starting or continuing their courses in Bangor had to be informed and allocated lodgings, addresses being provided by the Bangor Registrar, E. J. Jones, author of the 'Road to Endor'. He also found accommodation for members of staff, many being taken in by residents, who had never before taken in paying guests, but were faced with the possibility of billeting child evacuees from Liverpool at 5s per child per week! The author recalls arriving at Bangor station at night in 1939, to be greeted by Wood and Miss Radley, and sent to Erw Coed in Deiniol Road, where he lodged with J. E. Fleetcroft, another physics student, and two others. Mrs. Williams, the landlady after serving a meal, always left the room with "If you want more bread and butter, please ring the bell"! After Christmas Fleetcroft and the author were very fortunate in being taken in by H. I. Jones, one of the Bangor physics lecturers.

Wood (Appendix iv) states that he thought the choice of Bangor was "singularly fortunate, for the Professor of Physics there, E. A. Owen, had been registered as a postgraduate student in the College, during the period October 1915 to July 191 and had been awarded the Carey Foster Research Prize in June 1918. During these years he had been engaged on the standardisation of scientific instruments for the Ministry of Munitions so that his research at the College could be carried on only on a part-time basis. Nevertheless the writer came to know him fairly well and acquaintanceship was kept alive by occasional meetings during the seven years he spent as Head of the Radiology Department at the N.P.L. and after his appointment, in 1926, to the Welsh Chair. Unhappily these anticipations of smooth co-operation were not fulfilled and the relations between the writer, who had charge of the Physics unit, and the Professor were rarely free from difficulties. These were partly real, e.g., arising from the pre-war neglect to make any arrangements regarding the payment of running costs, and partly subjective, arising perhaps from the fear of the Welsh Faculty of Science that it might be overwhelmed by its visitors. Co-operation between the other members of the two staffs was much easier, notably that between Dr. P. Wright of Bangor and Dr. R. C. Brown who shared the intermediate work in a most amicable manner. A few of the General Degree lectures were shared also and, at first, the senior practical work, otherwise the lectures for the University College London students were all given by the members of its staff. ...

By 1942 it was decided that, if possible, an independent laboratory for the UCL post-intermediate students should be set up and, when it became known that the tenant of the cycle shop at 164 High Street would be pleased to relinquish his lease, it was taken over in the September of that year. By November the necessary alterations had been made and work started. The alterations included the installation of the usual laboratory services - water, gas and electric power - and the provision of an extra lavatory on the third (top) floor. The wiring for electric fires and for charging accumulators was done by Thomas, the UCL electrician, who came to Bangor for that purpose; Rowe and Tayler did as much as was possible, including the erection of a dark room on the top floor and blocking out the shop windows so that students could work unobserved by passers-by, while the necessary painting was done, very slowly, by two Bangor workmen, one 78 and the other 80 years old. ... Extra equipment was required - not only apparatus but benches, sinks, electric fires and a small lathe. Rowe went to London, spent four days selecting this apparatus and arranging for a large lorry to carry it to Bangor by road. Later smaller quantities of apparatus and books belonging to members of the staff were packed in tea chests and sent up in the same way. ... This improvised laboratory served excellently both for teaching and for the final examinations, one of which, owing to an oversight of the writer, had to be held on a Sunday morning since the students concerned were on the point of going down for their summer vacation." The photograph shows part of the inside of this laboratory, with Rowe standing at the door of his partitioned room. (H. & N. 349:188).

Having been absent with rheumatic fever and pericarditis during the second and third terms of the 1938-9 session, the author was lent Wood's notes on heat and thermodynamics, and on his advice attended some lectures given by E. A. Owen, H. I. Jones and P. Wright to the third-year Welsh students, as well as the appropriate special lectures given by R. C. Brown, Duncanson and Wood. The instructions for the six-hour special experiment in the final examination were as follows:-
"Arrange for a mercury pellet, of length l, to move in a horizontal capillary tube under a difference of pressure p applied by the air on each side of it. Find how the velocity v of the pellet varies with l and p. Use your results to find how dp/dv varies with l."

After the announcement of the degree results in the summer of 1940, the author was offered a post to assist Chalklin at Aberystwyth, but declined this in favour of joining Andrade and Vick at the the Directorate of Scientific Research, Ministry of Supply, in Savoy Hill House. There he met many physicists he had read about as a student.

During the war students were generally granted deferment from national service for only two years, and many were financed by the State Bursaries established to ensure an adequate supply of graduates trained in electronics, then a compulsory part of the physics course. There were 25 such bursars when the scheme was introduced in the 1941-2 session, the lectures and practical work in electronics being arranged in conjunction with Professor W. E. Williams of the Department of Electrical Engineering, and conducted by him and Dr. G. S. Brayshaw, who was appointed in 1941 an Assistant Lecturer in Radio Communications. After graduating in 1942, G. R. Heyland was appointed as a temporary Assistant Lecturer to help with the work. Most of the apparatus for the course was provided by the Government and was shared out between the two Colleges afterwards.

During the exile in Bangor Duncanson continued to collaborate with Coulson in a series of papers on the momentum distribution in molecular systems, his own contributions being on single bonds in which there is hybridization, with particular reference to the C-H bond; the hydrogen molecular ion; and the shape of the Compton line for lithium and nitrogen: with Coulson, there was a paper on carbon and the C-H bond; one on the shape of the Compton line for methane, ethane, ethylene and acetylene, and another on the shape of the line for methane. They also wrote papers on molecular wave functions for lithium, and atomic wave functions for the ground states of elements from lithium to neon. Duncanson also published some new values of the exponential integral, and wrote on the dimensions of physical quantities and allied topics. R. C. Brown published a paper on 'Fundamental Concepts of Surface Tension and Capillarity', and began to write a five-volume textbook for Longmans on the principles of physics up to the standard required by the H. S. C. (later A-level) and Intermediate examinations; he also continued his pre-war practice of contributing the articles on 'Surface Tension' to the Physical Society's Reports in Progress in Physics. G. B. Brown wrote papers on 'A New Treatment of Electric and Magnetic Induction'; 'A New Treatment of the Theory of Dimensions'; 'A Dynamical Treatment of the Elements of Heat'; and on the method and philosophy of science, as well as starting to write his book for Allen and Unwin on Science: 'Its Method and Philosophy'.

At the end of the 1943-44 session the Chemistry Department returned to Gower Street from Aberystwyth, Chalklin and E. S. Halberstadt, a chemistry graduate appointed as a Demonstrator in 1943 to assist him, accompanying them; Tayler also returned to help with the subsidiary course. The Bangor contingent returned to Gower Street in December 1944, rejoining Andrade who had already left the Ministry of Supply. Gibbs returned to College, but Vick went to Manchester to join Blackett as a senior lecturer. He was created O.B.E. in 1945 for his war work, became Professor of Physics at the University College of North Staffordshire (later Keele University) in 1950 and in 1959 moved into atomic energy administration, becoming Director of A.E.R.E., Harwell; finally he became President and Vice-Chancellor of Queen's University, Belfast and was knighted in 1973.

Back in Gower Street

During the war U.C.L. suffered more air-raid damage than any other British University or College. In September 1940 the Great Hall and the Carey Foster laboratory were entirely destroyed; the Gustave Tuck and the Applied Mathematics theatres, and the Library, north of the Dome, were gutted. Another air-raid in April 1941 led to considerable destruction by fire of the main building south of the Dome, and of the Dome itself. Photographs on pp. 181-187 of Harte & North show part of the war damage, nos. 339 and 341 referring to the Carey Foster laboratory. Wood records that much of the apparatus, which had not been taken to Bangor, had been damaged or stolen, but the Junior laboratory in Foster Court, which had been used by the St. Pancras A.R.P., was in good condition. The Works Department had removed most of the debris from the main building, and replaced the broken-window glass with translucent yellow plastic material. However most of this was blown out shortly afterwards by blast from the explosion of the V2 rocket, which caused so much destruction and loss of life at Smithfield market. (W.74). R. C. Brown in a note to the author recalls that in the early part of 1945 the bombardment by these rockets, which landed and exploded before their approach was heard, added a weird dimension to life in the capital. While lecturing one had to make a conscious effort to dismiss the thought that at any instant the theatre might be obliterated.

Research

On his return to College Andrade soon started to resume research, taking over the Birbeck laboratory, and part of the pre-war senior laboratory (in the old Anatomy dissecting room). The site previously occupied by the Carey Foster laboratory and the Memorial Hall was excavated to the level of the basement floor and three 'temporary' concrete huts were erected for the department. These were to have been ready in September 1946, but they were not finished until February 1948. They provided accommodation for Andrade and several of the staff, research rooms, a small workshop, a store room and a photographic processing room. In order to record his achievements in the five-year period 1945-50, there follows necessarily some repetition of the research in the fields of viscosity, creep, and single crystals recorded under those headings earlier. An additional Chair in Physics was approved at the Council meeting on 10 July 1945, but, at the meeting on 29 June 1948, approval was given for the establishment of a Readership in Physics, in the first instance instead of the additional chair, for the promotion and supervision of research in metal physics, and assistance in administration of the whole department. Mr. R. King, from the Royal Aircraft Establishment, Farnborough, was appointed to this post and took up his duties in April, 1949. Apparently the departmental grant increased from £1300 in 1945 to £4050 in 1950.

Dodd, who had worked on fuzes at the Royal Society Mond Laboratory, Cambridge, from 1940-42, and then at the Armaments Design Department, Fort Halstead, returned as a Lecturer in 1945, and resumed his pre-war work with Andrade on the effect of an electric field on the viscosity of liquids; thereafter, on graduating, J. Hart took over from Dodd to complete the investigation. E. R. Dobbs, an ex-wartime student, returned to the department and, with Andrade, applied the oscillating sphere method to determine the viscosities of liquid lithium, rubidium and caesium. A. J. Kennedy, another ex-wartime student, who had risen to the rank of Major in the Royal Corps of Signals, built a 'telephone exchange' to operate the automatic recording apparatus for the study of flow and recovery in metals with Andrade. Kennedy, who was made an Assistant Lecturer in 1947, devised a method of fitting the Andrade creep equation to experimental results, and studied the effect of instantaneous pre-strain on the character of creep in lead polycrystals. The author, who had spent the last two years of the war at the Armaments Research Department, Fort Halstead, with Professor W. E. Curtis, rejoined the department as an Assistant Lecturer in October 1945, and investigated the mechanism of dilatancy with Andrade; also he determined the onset of turbulence in certain arrays of particles. R. F. Y. Randall, another ex-wartime student, who had also joined Vick at the Ministry of Supply and then W. H. J. Childs at the Armaments Research Department, returned to the department in 1945 to work with Andrade on the effects of the surface condition on the plastic yield strengths of single crystals; M. J. Makin, who graduated after the war, stayed on to join them in the work on the Rehbinder effect. C. Henderson, yet another ex-wartime student, rejoined the department in 1946 and carried out with Andrade the single-crystal work on silver and gold, making the important discovery of the linear region ('easy glide') in the beginning of the plastic part of the stress-strain curve. Henderson also wrote a paper on 'The Application of Boltzmann's Superposition Theory' to Materials exhibiting Reversible Beta Flow, which Andrade communicated to the Royal Society. K. H. Jolliffe stayed on after graduation to start with Andrade their important series of experiments on the flow of polycrystalline metals under simple shear.

At the suggestion of Andrade, Dodd worked on the supercooled liquid state, studying viscosity and density with Pak Mi Hu; dielectric loss and dielectric constant with G. N. Roberts; the surface tension of phenyl ether; and the electrical resistance of liquid gallium in the neighbourhood of its melting point. R. E. Jennings, who was appointed an Assistant Lecturer in 1946, made an X-ray diffraction study of mercury in the neighbourhood of its freezing point with Andrade. R. K. Eisenschitz, who joined the staff as a Lecturer in 1946, worked on the theory of liquids, publishing papers on 'The Effect of Temperature on the Thermal Conductivity and Viscosity of Liquids', and on 'The Steady Non-Uniform State for a Liquid', before taking up a Readership in Theoretical Physics at Queen Mary College in 1949.

G. B. Brown, promoted to Reader in 1946, continued with his contributions on the method and philosophy of science, and R. C. Brown, promoted to Senior Lecturer in 1945, developed a new drop-weight method for the comparison of surface tensions with H. McCormick. G. C. Curtis, son of Professor W. E. Curtis, who was appointed an Assistant Lecturer in 1946, devised an electrical instrument for solving second-degree algebraic equations. Duncanson continued his collaboration with Coulson, working on electron momenta in atoms, and on atomic binding energies. With Heyland, who had been promoted to Lecturer in 1947, he undertook an experimental investigation of the absorption of cosmic rays in lead, and then a determination of the momentum distribution for cosmic ray mesons up to 6 KMeV/c. He was promoted to a Readership in 1948. Letitia Chalkin was made an Assistant in 1944 to work with her husband, Frank, but the partnership moved to New Zealand in 1946, when Frank was appointed to the Chair of Physics at Canterbury University College, Christchurch. Unfortunately he was killed in an aircrash at Singapore in 1954.

Andrade was delighted when the Physical Society met in the department on 4 February 1949 under the presidency of G. I. Finch. The following papers were read and discussed:- 'A projection model to illustrate crystal structure with surfaces of misfit' (Andrade); 'The mechanism of dilatancy' (Andrade & Fox); 'The effect of pre-strain on the character of the creep of lead' (Andrade & Kennedy); 'The thermal etching of single crystals of cadmium' (Andrade & Randall); and 'Viscosity and density in the supercooled liquid state' (Dodd & Pak Mi Hu).

Teaching

From 1945 to 1947 the pre-war lecture arrangements were followed, with the exception of the introduction of a special class in Mechanics for Intermediate students who had not studied the subject earlier. This class at 9-10 a.m. on Thursdays was taken by R. C. Brown, who continued to be in charge of the Biological group. The author recalls a visitation from Andrade and Wood at 10.30 one morning asking whether he would be prepared to take over R. C. Brown's 12.00 lecture; thus he gave his first lecture in the department, using R. C. Brown's notes, and continued to deputise for him until his return from a period of quarantine imposed by his son's attack of scarlet fever. He was already taking the Saturday morning practical class for this group of students. Details of the courses and lectures were not printed in the calendars, partly as an economy measure and partly owing to lack of detailed arrangements when the manuscripts went to press.

Students commencing to read for the B.Sc. (Special) degree in Physics in October 1947 and afterwards took their course under new regulations specifying an approved course of study extending over not less than than three years. To qualify for admission to the course a student must have matriculated, and must either have possessed a Higher School Certificate with passes at an approved standard in Physics, Pure Mathematics, Applied Mathematics and one other subject chosen from the following list:- Chemistry, General Principles of Biology, Botany, Geology, Zoology, Latin, Greek, English, French, German; or have passed the Intermediate examination in any of the four subjects in which he had not so qualified. Students who took the combined subject Pure and Applied Mathematics at a Higher School Examination were required to have attained a higher standard in the examination than was demanded of those who took the separate subjects in Mathematics, but they were required to pass in only one other subject additional to Physics. In addition to Physics the course included one in Mathematics extending over not less than one year. To qualify for the degree it was necessary to pass:-
(a) a test on translation into English of scientific texts in two languages selected from French, German, Italian, Russian, Spanish, the use of a dictionary being permitted during the test.
(b) the examination in Mathematics, normally taken at the end of the first year.
(c) Part I of the final examination in Physics, normally taken at the end of the second year.
(d) Part II of the final examination in Physics, normally taken at the end of the third year.

The Part I examination consisted of five three-hour papers on Properties of Matter and Sound, Heat and Thermodynamics, Optics, Electricity and Magnetism, and Modern Physics respectively. These papers were common to all internal students, except those of Imperial College, and were set and marked by small groups of teachers appointed by the Board of Examiners, a Sub-Committee of the Board of Studies in Physics. There were also two six-hour practical examinations, denoted as 'alternatives' when set by individual Colleges for their own students. These practical examinations followed the previous practice of involving the performance of a routine and a problem experiment respectively. Part II of the examination comprised not less than two, or more than four, three-hour written papers, and one six-hour practical examination. The department set two theory papers and a problem experiment performed by all the candidates in the practical examination. These problem experiments involved much preliminary work by the laboratory technicians in constructing the requisite number of pieces of specialized apparatus, one set for each candidate. All papers, common or alternative, had to be approved by two External Examiners nominated by the Board of Studies; these Examiners were also required to inspect marked scripts and approve the classifications of the Board of Examiners.

In the 1947-48 session the subsidiary course in Physics was replaced by one and two-year courses in Physics ancillary to a special degree in another subject, these ancillary courses having syllabuses appropriate to the main subject for which they were intended. Physics students had a one-year ancillary course provided by the Department of Mathematics. In this session the labelling of the courses was changed to I for Intermediate, G1 and G2 for first and second-year General, A1 and A2 for first and second-year Ancillary, and S1, S2, S3 for first, second and third-year Special Degree, courses.

The Foster Court laboratory sufficed for all the post-intermediate laboratory work until the erection of an Orlit hut in the courtyard adjacent to the laboratory relieved the inevitable overcrowding. This hut became the third-year laboratory in October 1949, when the third-year courses, under the new regulations, first came into effect.

Resignation

At the Professorial Board meeting on 18 October 1949, Andrade announced his wish to resign the Quain Chair from 31 December 1949 to take up his appointment at the Royal Institution. The minutes of the meeting recorded "The Board appreciated the distinguished services to science and the College which Professor Andrade had performed, and greatly regretted his departure". His offer to assist the College in a part-time capacity until the end of the session was accepted at a fee of £1250, half the then maximum professorial salary. Gibbs was appointed Acting Head of Department for the second and third terms of the session. King and Kennedy resigned at the end of the session to join Andrade at the Royal Institution, King becoming Assistant Director of the Davy Faraday Research Laboratory and Kennedy a R. I. Junior Research Fellow; Walden also accompanied Andrade.

At the Royal Institution and afterwards

On being appointed Director of the Royal Institution, Resident Professor, and Director of the Davy Faraday Research Laboratory, at the invitation of Lord Brabazon, Andrade had opportunities to continue with his researches, an environment appealing to his historical sense, and very pleasant living quarters. He had a long association with the Institution, having been a member since 1924, a Manager on several occasions, Vice-President, Chairman of the Library Committee, and a frequent lecturer there, including two series of Christmas lectures. Andrade entered into his new post with a zeal, but trouble might have been forseen and did in fact soon develop. There were two sides to the work of the Institution and the limits of authority of the Director were uncertain; the possibility of personal conflict existed. Unhappily a series of sharp disputes led him to resign in May, 1952, and it was not until March of the following year that the last of the story was heard, when his application to the Chancery Court for the matter to be remitted to the Arbitrator for reconsideration was rejected.

Out of office, Andrade worked as a research consultant until 1957, when Professor J. G. Ball invited him into his Department of Metallurgy at Imperial College as a Senior Research Fellow. Walden rejoined him on his favourite subject, the creep of metals, and some remarkable discoveries were made, as recorded earlier. This work continued at full stretch until 1971, and he was even trying against great odds to prepare a paper for the Royal Society only three weeks before his death at the age of 83 on 6 June 1971. A full-length obituary, with photograph, dominated the obituary page of 'The Times' on the following day. There is a good pre-war photograph of him reproduced by Harte and North (loc. cit. 387;201).

Andrade: concluded

Before the war the entrance to the department had a notice announcing that Professor Andrade does not see visitors except by appointment. Each Christmas he used to entertain the senior members of his staff to a notable lunch at the Savage Club or in the King Edward VII Room at Pagani's, and he gave a 'rag' lecture in the large theatre, crowded to capacity, and with Walden's assistance confounded the audience with his experimental demonstrations, many apparently defying physical principles. To his research students Andrade was 'The Prof', a somewhat awesome figure, rather brusque and sometimes caustic in his comments; however his forthright manner and his objectivity, combined with his enthusiasm for their work, won their admiration and often their affection. To celebrate his election to the Fellowship of the Royal Society in 1935, there was inaugurated the Carey Foster Laboratory dinners. These were organised by Kenneth Greenland, the first being held in the King's Room at Pagani's Restaurant on 28 February 1935. Andrade was always the guest, but he always insisted on paying for and choosing the wine. The dinners continued to be held at Pagani's until the outbreak of war, but after the war they were held elsewhere, the last one taking place at the Trocadero in 1950 and being reported in an evening paper! On his eightieth birthday a special party was arranged for him, and he was presented with a record player, on which he subsequently played mainly Mozart and Schubert. His letter to the author referred to the "delightful party... the generous and pleasing gift... the greatest pleasure to meet old friends and collaborators in such a spirit of friendship". It was signed, "Affectionate regards, Yours, Old Prof."

Andrade had a flair for collecting old scientific books, his collection being centred on the seventeenth century and especially on the works of Newton, Hooke and Boyle. It included an example of the first and second issues of the first edition of the Principia, as well as many subsequent editions, including the French one prepared by Marat; all the important works of Hooke, published in his lifetime; and examples of the first editions of Boyle's Sceptical Chymist and Gilbert's De Magnete. According to Andrade an inadequate pension forced him to sell most of the collection at Sothebys on 12 and 13 July 1965, thereby realising almost £70,000.

In 1936 he became a member of the Royal Society's Library Committee, succeeding to the Chairmanship on the death of Sir Charles Sherrington in 1944, and in July 1948, in recognition of his services and of his 'unrivalled knowledge of the older scientific literature', the Council created for him the office of Honorary Librarian, a special one-time appointment which was not to constitute a precedent. He was Chairman of the Council's Committee responsible for the publication of the correspondence of Isaac Newton, which had remained hidden for so long; he saw the first four volumes, covering the years 1661 to 1709, published and the fifth volume, taking the letters up to 1713, in an advanced state of preparation before he died. A Brief History of the Royal Society was written at the request of, and published by, the Society to mark its tercentenary in 1960.

Cottrell (loc. cit.) records inter alia "Andrade is seen at his best, as a historian of science, in his book on Newton. Written with all his characteristically elegant prose, this short biography, published in 1954, is still perhaps the best introduction to Newton and his work. Undoubtedly, however, Andrade's most important historical essay is his Wilkins Lecture on Hooke, which historians of science acknowledge as an indispensable starting-point for the study of the subject. Hooke commanded great admiration from Andrade, who perhaps saw some similarities between his own life and that of his subject; and he left no doubt where his sympathies lay in his accounts of Hooke's struggles with colleagues and other scientific personalities of that age. Andrade, a down-to-earth experimental physicist with formidable inventive skills in the design of apparatus and experiments, and with an almost wholly empirical approach to scientific research, recognized just these same abilities, at the level of genius, in Hooke; and it is this above all that gave him such a penetrating understanding of Hooke as a scientist, an understanding from which sprang his warm feeling for Hooke as a man."

As expositor of science at different levels Andrade was editor for physics of the fourteenth edition of Encyclopaedia Britannica; acted for many years as adviser to a firm of publishers; was science correspondent of The Times from 1945 to 1952; introduced speakers in the BBC's programme "Science Survey" in its original form; was a member of the Brains Trust; gave the BBC Television series, 'From Small Beginnings' (in which the author assisted and appeared on screen during the experimental illustrations); on three occasions gave the Christmas Lectures adapted to a juvenile auditory at the Royal Institution; and was a prolific writer of books, several of which had long histories. For example, 'The Atom', first published as a yellow-back "Benn sixpenny" lasted to provide a basis for 'The Atom and its Energy', published some twenty years later; 'An Approach to Modern Physics' is a lineal descendant of 'The Mechanism of Nature', first published in 1930, and translated into six languages. As well as other books of his own, including 'Poems and Songs', he was joint author with Julian Huxley of 'Simple Science', and with his wife, Mona, of 'The Answer is'.

Andrade served on the Council of the Royal Society from 1942-44 and was President of the Physical Society from 1943-45. Immediately after the war as Foreign Secretary of the Physical Society, he launched an appeal to establish a prize in honour of Fernand Holwick, the Director of the Curie Laboratory of the Radium Institute in Paris, and of other French physicists who also met their deaths during the occupation of France in 1940-44. The Holwick Prize was thus created and the Société Francaise de Physique responded by founded a Holwick Medal for presentation to the prizewinner, the two Societies agreeing that the Prize and Medal should be awarded annually, and given alternately to French and British physicists for distinguished work in experimental physics.

Many honours were conferred on Andrade; he received an honorary Ll.D. from the University of Edinburgh in 1950, and honorary D.Sc.s from the Universities of Durham and Manchester in 1952 and 1956 respectively. The award of the Holwick Prize and Medal in 1947 gave him especial pleasure. Other honours included the Grande Medaille Osmond, Société Francaise de Metallurgie, 1951; the Hughes Medal of the Royal Society, 1958; and the Mitchell Medal of the Association of Engineers, 1962. He became a Chevalier de la Légion d'Honneur in 1949; a Membre Correspondant, Académie des Sciences, Institut de France; and a Membre d'Honneur, Société Francaise de Physique. References have already been made to his giving the Guthrie Lecture of the Physical Society in 1941 and the Wilkins Lecture of the Royal Society in 1949; he also gave the Rutherford Memorial Lecture in Australia in 1957.

Two outstanding members of the department, namely Nicholas Eumorfopoulos and Dudley Orson Wood, whose combined memberships of the College total 104 years, clearly deserve some further accounts of their contributions. Furthermore there must be some reference to Leonard Walden, Andrade's right hand assistant on the research side of the department.

Nicholas Eumorfopoulos

'Eumo', as he became to be affectionately called, was a member of a well-to-do Greek family living in the Bayswater area. He was educated at University College School, then housed in the South Wing of the College, and entered the department as a student in 1889 under Carey Foster, taking his B.Sc. degree in 1892. After two years of postgraduate study he was appointed Demonstrator in 1894, Assistant in 1904, and Honorary Research Assistant in 1920, following the resignation of his Assistantship, since he wished to devote more of his time to research and his involvement with the Men's Union Society. He was elected a Fellow of the College in 1900.

According to Wood (in an Appendix), he disliked lecturing, but was an excellent demonstrator and a very skilful and painstaking experimenter. For many years he was in charge of the senior laboratory and wrote nearly all of the manuscripts describing the procedures to be adopted in performing the experiments set up in it. Moreover he provided elaborate tables for each experiment giving correct measurements and even results based on correct evaluation of somewhat erroneous data! All of his research was on heat, his first paper in 1895 dealing with the thermal conductivity and emissivity of metals. In the following year there appeared his paper with Professor Ramsay on the determination of high temperatures with the meldometer; then in 1901 there appeared with Callendar a paper on the expansion of platinum and silica; and this was followed in 1912 by his paper on the expansion of mercury and quartz. Between 1908 and 1914 he published three papers describing his determination of the boiling point of sulphur, one of the fixed points on the International Temperature Scale. In 1909 he started the porous-plug experiments using an alundum disc glazed round a peripheral ring to minimise the error due to radial conduction from the circumference inwards; thermocouples connected in series were used to measure the temperatures and an elaborate mercury pressure gauge, designed by Kamerlingh Onnes, was used for the pressure measurements. In the mechanical part of the work he was assisted by Ackroyd, an engineering graduate, and in the final stage of the experiments he was joined by Rai, a keen and skilful Japanese naval officer attached to the Japanese Embassy. The work was not completed until 1926 by which time other results by the Americans, Hoxton(1919) and Roebuck(1925), using cylindrical plugs, reduced its importance. Rose Innes made an initial contribution of £300 towards the cost of the apparatus, and apparently paid Ackroyd £300 p.a. for his work on it. Only one of his notebooks has survived; it contains observations and calculations in wonderfully neat handwriting made during his use of the Callendar compensated gas thermometer to determine the boiling point of sulphur.

The UCL Annual Report (1942-43) records that having inherited strong business interests, 'Eumo' came into his own in dealing with the complicated affairs of several branches of College life, and the value of his work in securing the smooth conduct of their finances cannot be over-estimated. In 1912 he became Honorary Treasurer of the Union Society and continued in that office until his death. His connection with the Union became very intimate and his interest in its activities deepened. He was one of the most familiar figures at the Annual Athletic Sports, being a keen supporter of that side of student life. The Eumorfopoulos Cup for the Squash Club is one of the many instances of his private generosity, and by invitation he performed the opening ceremony, on 17 October 1935, for the new Squash and Badminton Courts, with adjoining rooms for the Presidents of the two Union Societies. In recording the successful negotiations for the sale of the Perivale Athletic Grounds and the purchase of new grounds at Shenley, the College Committee recorded (Annual Report, p.93, 1939)....'Without his lively interest, his wisdom, his experience, and his untiring devotion it is not likely that such a satisfactory solution of the Athletic Ground problem could have been reached.' 'Eumo' was Honorary Treasurer of the Professors' Dining Club and the Old Students' Association (of which he was a Past President). In 1939, on the completion of fifty years of his connection with the College, the Union Societies, the Old Students' Association and the Hospital combined in raising a fund to commemorate his work for the students by the erection of ornamental gates to the new Athletic Ground, the 'Eumo' Gates. The project was deferred by the war.

Wood (loc. cit.) records that 'Eumo' was a great stickler for the proprieties, amiable and very generous. Before the 1914-18 war he always came to college in a top hat and morning coat and did not wear overalls in the laboratory. He lived with his two sisters in Pembridge Gardens, where he had a billiards room lined with bookcases containing beautifully bound books relating to Napoleon, whom he admired intensely, and a good wine cellar. Although he never went to Greece before 1914, he took a great interest in its politics, and in the Russian ballet which flourished at Covent Garden in those days.

The Annual Report (1930-31) acknowledges his valuable gift of books to form the nucleus of a departmental reading-room; that for 1942-43 records 'Like others whose roots went deep into the past history of the College, its traditions were sacred to him, and its War injuries and enforced evacuation caused him great sorrow. So long as his health permitted, he continued to pay regular visits to the deserted buildings, where he would work on salvaged records and sometimes meet friends.' He died on 9 December 1942, the funeral service being held at the Greek Cathedral, Bayswater and attended by the College representatives - the Acting Provost (Mr.E. L. Tanner), Prof.H. O. Corfiato and members of the Union Society. There is a good photograph of him standing in the quadrangle, with one of the two observatories (built in 1905-6 for the start of practical astronomy) as background. (H & N. 335:171).

Dudley Orson Wood

Although Wood did not retire from the department until 1952, and continued to serve the College in a part-time capacity as its first Careers Adviser until 1961, it is fitting to include him at the end of the Andrade period. The son of a civil servant, Wood was educated at Latymer School, and at the Royal School of Science during Callendar's tenure of the Chair of Physics. He obtained his M.Sc. degree in 1916 by research, his thesis on the vapour pressure of concentrated sugar solutions, contains an addendum on a calorimeter for the measurement of latent heats of dilution at different temperatures, together with some preliminary test results for the specific heat and latent heat of dilution of concentrated sugar solutions. R.C.Brown in An Appreciation (Phys.Bull.17,1966,365) is of the opinion that the degree might well have been a Ph.D. if the University of London had instituted this degree earlier; however he goes on to record that Wood "was only really interested in or sympathetic towards the most important and fundamental physical researches". Joining the staff as an Assistant in October 1910, Wood served under five professors - Trouton, Bragg, Porter, Andrade, and Massey - becoming Senior Lecturer in 1921 and Deputy Director of Laboratories in 1931. He became a Fellow of the Institute of Physics in 1920, and of The Physical Society in 1924; for many years he was a faithful member of the Physical Society Dining Club; his longstanding membership of the UCL Professors' Dining Club was marked by a special retirement dinner on 30 June 1952, the menu being printed on the hand-press in the English Department and contained a characteristic photograph of Wood with pipe in mouth.

As Tutor to Science Students from 1934-52 and Senior Tutor from 1949-52, member of the Professorial Board from 1932-52, and member of the College Committee for two three-year periods from 1934 and 1943 respectively, he played a major part in college administration and policy making. At the university level he served as Secretary of the Board of Studies in Physics from 1928-52 and then as Chairman from 1952-61, and as Dean of the Faculty of Science from 1948-52. During the exile in Bangor he carried out the very demanding duties of the acting-headship of the department and tutorship of science students as well as taking his usual share of the teaching load.

Wood was deeply interested in historical studies and for many years he was a member of the Board of Studies in the History and Philosophy of Science, lecturing to postgraduate students in the UCL Department of the History and Philosophy of Science and supervising their dissertations. As recorded earlier, his research into the history of the UCL Department of Physics (preceded by his lectures thereon to student societies) inspired the present work.

For many years Wood was Joint Editor of Science Progress, but was strangely diffident about writing for publication, his contributions being limited to that journal, and to The Annual Register in which he wrote the pieces on 'The Physical Sciences' from the early twenties until the late thirties. "The lecture bench and the blackboard were his outstandingly successful means of communication, and many generations of students have had their approach to physics moulded and coloured by his courses in classical physics." (loc.cit.)

Wood did more examining than any other member of the department, setting and marking papers in physics from matriculation up to degree level. The author first met him at South Kensington in November 1936 when Wood was his examiner for practical physics in the external intermediate examination. For many years he was Chief Examiner for the Joint Matriculation Board's Higher School Certificate, followed by the Advanced Level, examinations; in that capacity he recruited the author as a member of his team for the 1946 H.S.C. examination. From 1952-62 he was Chairman of the State Scholarships Awarding Committee and from 1952-63 Chairman of the 'Mature Matriculation' Board.

Even after his formal retirement from the department at the end of the 1951-52 session, he lectured to the Intermediate students, continuing to the end of the 1956-57 session when the course was discontinued. Finally he established the first careers service in the College. The UCL Annual Report, 1960-61, reporting his retirement from the post of Careers Adviser refers to his "fifty-one years of notable and unbroken service as a member of the College staff...only a person of Mr. Wood's tireless energy could, after the official age of retirement, have succeeded as he has done in building up a careers organisation which now serves the students of nearly every College department. Many former students now holding interesting and responsible posts up and down the country, and beyond its borders, are indebted to Mr. Wood for his assistance in securing them."

In December 1966 he died suddenly at the age of 78. R. C. Brown concludes his appreciation as follows:- "Wood was an excellent conversationalist and enjoyed intimate social occasions .... but the wider circle of those with whom he worked during the course of his many and varied activities will remember chiefly his penetrating mind, his strong and sincere convictions and his absolute honesty of purpose." On the photograph of the UCL evacuated staff at Bangor (H & N. 350;189), Wood is shown, seated fourth from the right, on the front row.

Leonard Walden

In a letter to Wood, Walden recalls becoming a laboratory boy at the age of thirteen in the Chemistry, Explosives and Metallurgy Department of the Ordnance College at Woolwich. At sixteen he persuaded a drunken recruiting sergeant to enlist him in the Army at 7s per week, twice his previous pay. Nearly eighteen, he was wounded in the second battle of Loos on the Somme and at nineteen he was demobilized with the Cadre of the Regiment and Acting Sergeant Major. He went back to see some friends at his old laboratory, then part of the Artillery College, met Captain Andrade and remained with him until Andrade's death. In 1939 being on the Royal Society national register for scientific work, he was sent to H. M. S. Vernon, the Mining and Torpedo establishment at Portsmouth, as an Experimental Assistant, Grade I. There he was awarded one of the first George Medals for his work on a German Magnetic Sea Mine, a bar to the medal being awarded for later work on mines and the detection of booby traps.

Walden had a comprehensive knowledge of laboratory techniques and great skill in applying them. He rendered invaluable service to most of the research students in the Carey Foster Laboratory and then in the Birkbeck Laboratory and the huts erected on the old Carey Foster site after the war. Incidentally he was involved in the interior design of the huts, in particular the dark room. He was usually involved in the preparation of, and assistance in, the experimental demonstrations, especially those in the 'rag' lectures exhibiting unusual phenomena, that were a feature of Andrade's public lectures. In 1937 he published two papers, one on 'Instrument Suspensions' in the Journal of Scientific Instruments, the other on 'Cements and Waxes' in the School Scientific Review. In 1950 he went to the Royal Institution with Andrade, soon becoming the chief lecture assistant there. Later he followed Andrade to Professor Ball's Department of Metallurgy at South Kensington.

Hoddles Creek, 1908-20

Harrie Stewart Wilson Massey was born on 16 May 1908 in St. Kilda (a suburb of Melbourne), Australia, the only child of Harrie Stewart and Eleanor Wilson Massey. His parents had married in 1907 and, after a year in Tasmania, they returned to Victoria and made their home in La Mascotte, the small country house, built by Massey's maternal grandfather in the settlement of Hoddles Creek, on the Yarra river near Warburton, some fifty miles to the east of Melbourne. One of his earliest memories was being taken outside in his father's arms at 5 am in 1910 to see Halley's comet. He entered the state school at Hoddles Creek in 1913 and was awarded the Merit Certificate only four years later, having progressed through the requisite eight grades at twice the normal rate owing to his ability to learn every lesson as soon as it was given to him. Being so young, Massey had to remain at school, but his attendance was a mere formality since he was taking a correspondence course aimed at winning a scholarship to enter University High School, Melbourne, one of the best known state secondary schools in Victoria. The day on which he learnt he had been successful was one of the most exciting in his life; he ran all the way home from the post office in rapture.

Melbourne, 1920-29

On entering the High School in 1920 the twelve-year old boy informed the headmaster at interview that he wanted to be a university professor of science! Apparently Latin was his best subject in his first year, but afterwards he developed a very considerable interest in mathematics, and it was only after he started to do chemistry that he became really enthusiastic about a branch of science other than the sort of astronomy that had interested him earlier. He was delighted to find that the various materials could be classified in systematic ways, in terms of the properties of relatively few elements. It was during his last year at school that he became interested in physics as well owing to the realisation that light and electricity and magnetism are closely related.

In 1925 Massey entered Melbourne University, having won a scholarship. Academic standards were high, Fellows of the Royal Society being in charge of the Departments of Chemistry, Natural Philosophy and Mathematics. At first Massey leant towards chemistry, but was influenced towards physics by the systematic and thorough first-year course of lectures given by E. O. Hercus. Apparently Professor T. H. Laby, the head of department, who would normally have given the course, was away on leave. Perhaps this absence was fortunate for the development of Massey's career, since in his otherwise affectionate 1980 Laby Memorial Lecture (Aust. Physicist, 17, 181-187) he said "In a fairly wide experience I would rate him the worst lecturer I have heard." He described Laby's third-year lectures on X-rays "as largely consisting of him just reading aloud from Compton's 1926 book on the subject and as being quite unbearable in their tediousness." Massey took the honours courses in chemistry and physics, winning a succession of prizes and scholarships, and graduating with a first-class B.Sc. degree in 1927; he also had time for billiards, tennis, baseball (at which he represented the University), and cricket. He continued with mathematics, gaining a first-class honours B.A. degree in 1929. He attended a course of lectures on the new quantum mechanics in the department of mathematics, and, although he was attracted to organic chemistry, he had now firmly opted for physics. A post in industrial research, brought to his notice by Laby, did not interest him; his goal was a university professorship. The Ph.D. degree was not then available in Australia, so in January 1928, during his B. A. course, he began work for the M. Sc. degree in the Department of Natural Philosophy, this involving an experimental project and a theoretical dissertation. The experimental project was on the reflection of soft X-rays from metal surfaces and was carried out jointly with C. B. O. Mohr - the beginning of a long fruitful partnership. For the dissertation Massey had in mind, The Atomic Nucleus, but on Laby's suggestion elected for Wave Mechanics. In his 1980 lecture (loc. cit.) Massey commented "For me this was an inspired proposal although neither of us had the slightest appreciation of what was involved. I embarked on it with enthusiasm but soon found what a gigantic task it would be. Every issue of the Proceedings of the Royal Society and the major German journals, the Zeitschrift fur Physik, the Annalen der Physik and the Physikalishe Zeitschrift was full of papers applying or developing wave mechanics...I had to glean from the papers in German not only the new results but often the background of a subject in physics of which I was previous unaware. An iterative process in which I used the mathematics to interpret the German and thence the German to discern the physical content began to work after a slow and wearisome beginning. In the course of preparing the dissertation on such a wide range of physics I learnt much that has proved invaluable to me for a career of research in modern physics." The dissertation occupied over 400 pages and still holds an honoured place in the departmental library. To ensure the proper appreciation of the dissertation Laby took the then unusual step of having an external examiner, choosing R. H. Fowler F.R.S. whom he knew was to be Massey's formal supervisor when he went to Cambridge. The effort involved in the preparation of the dissertation was remarkable not only because of Massey's poor linguistic ability but also of his need for extra money, which involved a heavy burden of tutoring at the university and coaching at the local school, since he had married while an undergraduate, and moreover found time to indulge in his enthusiasm for ball games.

Cambridge, 1929-33

Early in 1929 Massey was awarded the second Aitchison Travelling Scholarship, which included a leisurely first-class voyage to Tilbury, and in 1931 he received a 1851 Senior Research Scholarship. Without hesitation he proceeded to the Mecca of all physicists at that time, to the Cavendish Laboratory, Cambridge, to work under Sir Ernest (soon to become Lord) Rutherford, President of the Royal Society. Massey entered Trinity College, which incidentally he thought too big. Before leaving Australia he had already decided that his main field of study would be collisions, but he was undecided between theory and experiment, and L. H. Martin, who had recently returned from Cambridge, had advised delaying the choice as long as possible. Before unpacking his bags Massey went to see Rutherford (without the formality of an appointment) and the great man, who had just returned from South Africa, proceeded to discuss the deck games played during their voyages. Turning to research he expressed grave doubts about Massey's wish to pursue both theoretical and experimental work and advised waiting for a term. This he did to the extent that he confined himself to theory for the first term. Although University regulations required Massey to have a supervisor (R. H. Fowler) he was already an independent researcher. D. R. Bates in his 'H. S. W. Massey, life, work, personality and characteristics' (Fundamental processes in atomic collision physics; ed. H. Kleinpoppen; Proc. NATO Summer School 1984; New York:Plenum Press) reckons that Massey did enough work at Cambridge for six Ph.D.s and one D.Sc. on problems, with two exceptions, found for himself in largely unchartered territory, his only computational aid being a cylindrical slide rule.

In October 1929 E. C. Bullard, at the suggestion of P. M. S. Blackett, began an experimental investigation of the angular distribution of electrons scattered by argon atoms to see what light this threw on the Ramsauer effect - the total cross-section for electrons scattered by gases decreased as the energy was reduced below about 30 eV. In February 1930 after Bullard had started to set up the apparatus Massey asked if he might join him; Bullard was delighted since the work would proceed much quicker with an extra pair of hands. Previously reliable angular distribution measurements had been made only up to scattering angles of 60 deg and had merely shown the scattered intensity falling off monotonically with increase of scattering angle. Bullard and Massey rather more than doubled the maximum scattering angle and thereby obtained unmistakable evidence for the wave behaviour of electrons scattered by argon atoms, the monotonic fall off giving way to a rise to a maximum. Bates in Massey's Royal Society Obituary (B.B.D.) records Bullard's account of the collaboration including "I remember very clearly the day when we found the critical result. I was moving the collector round in 5 deg steps and Massey was reading the electrometer (a venerable relic) which measured the collected current. The current, as always, fell rapidly as we went away from the main beam; then, suddenly, Massey said 'You've turned it the wrong way, the current has gone up'. I said 'I haven't' and we repeated the measurement. We had found a peak in the scattered current at an angle around 90 deg from the main beam. It is rare to be able to recognise a significant new observation as it is made, in fact I can only think of one other example in my experience. It was not difficult to see the analogy of our peak with the diffraction rings around a street lamp in a fog and the explanation of Ramsauer's results as diffraction around a spherical atom. We had a phenomenon that was clearly wave mechanical and quite inexplicable by the classical theory of collisions. Now (1978) it all seems rather trivial and obvious, but at the time it was a nice thing for two young men to find. We wrote it up quickly." By integrating the angular distribution curve at different energies to obtain the total cross-section good agreement with Ramsauer was shown by Massey. Bullard and Massey then extended the measurements to helium, neon, nitrogen, hydrogen and methane, and explained their results on the quantal theory of scattering. Later, with E. C. Childs, Massey extended the measurements to include cadmium and zinc atoms after emergence from a hot oven; once again results in agreement with quantal scattering theory was obtained. Bates (loc. cit.) takes pains to avoid the impression that Massey was primarily a theorist who early in his career did enough experimental work to determine where his preference lay. He ascribes the greater part of his personal theoretical research at least to some extent by force of circumstances: his first two university posts were in mathematics departments, and when in 1950 he became Quain Professor there were such heavy demands on his time that it was impossible for him to engage in the experimental research he loved. To help redress the balance slightly he quotes Massey's account of his glass-blowing experience with Pyrex, when it was first used in 1932 instead of soda glass for vacuum envelopes and associated equipment.

With Bullard, Massey applied the Born approximation and Thomas-Fermi field to calculate the angular distribution and total cross-section for fast electrons scattered by a heavy atom, obtaining results capable of representation by two curves. Then, with Mohr, there followed a long complicated analysis to obtain closed expressions for the excitation of the 1s to nlm transitions of hydrogen by electron impact. In a companion paper they also worked through the lengthy and difficult algebra required for the corresponding ionization transitions. Adapting their cross-section formulae to helium (and to molecular hydrogen in the case of ionization), they made a detailed comparison with measured excitation and ionization cross-sections, thereby obtaining a timely assessment of the reliability of the Born approximation. Massey had already applied the Born approximation to collisions between electrons and polar molecules, showing that it gives the correct J = 1 cross-sections provided that the dipole moment is not too large; he recognised that these cross-sections are likely to exceed the elastic cross-section.

When Oppenheimer introduced electron exchange in 1928 he did not extend the theory beyond the stage of general results, but suggested that its neglect was responsible for the failure of Faxen and Holtsmark to reproduce the Ramsauer effect in their 1927 calculations. However by allowing for the polarisability of the target atom, Holtsmark satisfactorily explained the effect and also gave a good representation of the measurements of Bullard and Massey on the angular distribution of the scattered electrons. Massey and Mohr first treated exchange quantitatively; their calculations on the excitation of the 2³S, 2³P, 3³P and 3³D terms of helium, and on the dissociation of hydrogen in the X¹_ to b³_u transition established that exchange allows multiplicity change transitions to be strong, a result of prime importance. As they noted, the success of Holtsmark, while ignoring exchange, now seemed puzzling. To resolve the problem they considered the effect of exchange and the replacement of the plane wave of the Born-Oppenheimer approximation by a wave distorted by the static potential of the target atom, showing that Holtsmark's success was due to the cancellation of the effects of exchange and distortion in elastic scattering. The problem of including both exchange and distortion in calculations of inelastic collisions remained. Massey and Mohr made progress at high energies, where the effect of exchange is slight, and at moderate energies, where the exchanged and directly scattered waves are of comparable intensity and interfere strongly. They succeeded in obtaining numerical results for the excitation of the 2¹P and 2³P terms of helium. They also showed that the theory is adequate to account for the maxima and minima found experimentally in the angular distribution of electrons inelastically scattered by heavy atoms.

Massey applied the Born approximation to the elastic scattering of electrons by molecular hydrogen. He showed that the differential cross-section, averaged over all molecular orientations, is a function of vsin(J/2), where v is the velocity and J is the scattering angle, and he did computations which revealed diffraction effects. Massey obtained similar diffraction effects in the scattering of short X-rays by molecular hydrogen. With Mohr, he established that there is a close relation between X-ray and electron scattering and gave a simple formula expressing this relation. They also greatly extended the range of Massey's Born approximation calculations on the elastic scattering of electrons by molecular hydrogen, the final formula showing the scattering by the two atoms separately, the relatively unimportant scattering by the concentration of charge between the nuclei (which produces the molecular binding), and a straightforward diffraction factor due to the two scattering centres; it lead to satisfactory agreement with the experimental results of Bullard and Massey at energies above 80 eV. In the case of the elastic scattering by nitrogen Bullard and Massey went further, treating the scattering by the two atoms considered separately by the Faxen-Holtsmark method, while neglecting the scattering by the concentration of charge between the nuclei; the agreement obtained with their own measurements was good, except at small scattering angles, above 60 eV.

Massey, with R. A. Smith, studied collisions between atomic systems applying the wave version of Mott's perturbed stationary state method in its original form. They obtained the correct formula for the cross-section of the symmetrical charge transfer process, being the first to treat the symmetry properties of the system correctly. Their computation of the cross-section for 1 keV He⁺ ions in He was the forerunner in this field. Massey and Mohr recognising that the mobility of He⁺ ions in He is largely controlled by symmetrical resonance charge transfer, calculated this mobility.

The consideration of quantal effects in the elastic scattering of atoms and in transport phenomena in gases was pioneered by Massey and Mohr. In the first instance they represented the atoms by rigid spheres and discovered that the quantal elastic cross-section was twice the corresponding classical value as the wave length associated with the relative motion tends to zero owing to diffraction effects at unobservably small scattering angles. On the basis of the rigid sphere model they calculated the viscosity of helium as a function of temperature down to 15K, finding much better agreement with experiment than on the classical basis. The application of an interaction potential calculated by Slater produced no more improvement in accuracy.

Massey's third and fourth papers were on the effect of nuclear magnetic moments on the nuclei scattering of fast electrons, and on the anomalous scattering of alpha particles from the wave mechanical point of view; later he returned to alpha-particle scattering by atomic nuclei. Cockcroft and Walton having shown that lithium is disintegrated by fast protons, then reported similar disintegrations of heavier elements. Bates (loc. cit.) recalls a conversation with Massey in which he was told that R. H. Fowler asked him to investigate if a heavy element could react to the apparently observed extent with protons using a simplified model including resonance levels. He was able to avoid a tedious unrewarding calculation because a formula of Mott enabled a limit to be set to the contribution from a resonance level, this limit being far less than the observed result for heavy elements. Apparently this result was not published, and in 1933 Oliphant and Rutherford found that contamination of the target by boron from the Pyrex glass was responsible for the spurious results. Chadwick's discovery of the neutron prompted Massey to do further work at the frontier of nuclear physics. His account given to Bates runs as follows:- "...Rutherford (1920) had speculated on the possible existence of an atom of zero nuclear charge arising from very tight binding of an electron to a proton and their role in the building up of heavy nuclei. In the period immediately after the discovery of the neutron all that was known of the mass was that it was nearly equal to that of the proton. Rutherford's picture which would have required that the neutron should have a smaller mass than the proton was not ruled out as it was later on. Even though according to non-relativistic quantum mechanics the lowest state of an electron in the field of a charge of +e is the 1s state, at the time one could not be sure that a fully relativistic two-body theory might yield a much lower state. In default of any other basis I applied atomic collision theory to discuss the passage through matter of the neutrons envisaged by Rutherford." Bates points out that the section entitled 'Collisions of neutrons with atomic nuclei' in Chadwick's Bakerian Lecture (1933) is based largely on Massey's exploratory work. (B.B.D.)

Bates concludes his account of Massey's investigations while a research student with three miscellaneous papers, namely, 'The theory of the extraction of electrons from metals by positive ions and metastable atoms', 'The triatomic hydrogen H', and 'The theory of the extraction of electrons from metals by metastable atoms'.

Bates reserves the D.Sc. for Massey's contribution to the first edition of 'The Theory of Atomic Collisions'. Massey told him "that one day in 1931 Mott ('One of the most original people in Cambridge') strolled into the laboratory where he was working with Bullard: 'He asked me whether I'd be interested in joining him in a book he was going to write on collisions. I knew at once I would do it.' The invitation was a signal tribute to the standing that Massey already had at the age of 23. It offered him a marvellous opportunity and his response was marvellous." (B.B.D.). The first edition, published in 1933, ran to 283 pages; Mott wrote chapters 1-6 and 14 & 15, and Massey wrote chapters 7-13.

According to Bates "Massey's four years at Cambridge were blissful. Never again during his active life would he be able to indulge his enthusiasm for science free from the heavy pressure of teaching, administration or policy making. He regarded it as one of the greater privileges that could have befallen him to be there during that period, and in particular to have been there in 1932, the miracle year of Chadwick and the discovery of the neutron, of Cockcroft and Walton and the first artificial disintegration, and of Blackett and Occhialini and their confirmation of Anderson's identification of positive electrons among the secondary products of cosmic rays by their counter-controlled cloud chamber. Every detail of events he witnessed was securely stored in his superb memory, enabling him to recreate the scene perfectly....The excitements of science did not prevent Massey from indulging his passion for ball games. With Cockcroft he formed a mixed hockey team. He played for the Cavendish Cricket Club, becoming captain in his last year and leading his team to win the Inter-Laboratory Cup. Some of the score cards have survived. They prove that his legendary prowess at cricket was real: for instance in a match against Mr. Hoar's XI played on Parker's Piece, Massey retired on reaching his century (the next most successful batsman making only 19 runs) and then in six overs took four wickets for 24 runs, easily the best bowling performance on either side. Moving on a few years, when Massey lived in Belfast he played regularly for Collegians, one of the leading cricket clubs in Northern Ireland. A friend, J. J. Unwin, who was a keen follower of the game, opined to me that he was good enough to be a professional. On my mentioning this to Massey during our last meeting he brightened and said that the Australian Test wicket-keeper, B. A. Barnett, a fellow Victorian who knew him well, also thought this. He attributed his adeptness mainly to having an exceptionally fast reaction time." For several years after going to London, he played for the Chislehurst Club at weekends, and it was during this period that J. B. Hobbs presented him with the Hobbs bat for his prowess. Later, of course, he captained the U.C.L. physics staff side in the annual staff-student cricket match.

Queen's, Belfast, 1933-38

Massey finished at Cambridge in the middle of the great depression, when it was really a matter of luck what suitable job turned up first. In June 1933 he was appointed Independent Lecturer in Mathematical Physics at The Queen's University of Belfast, the head and only member of the Department of Mathematical Physics! This meant the end of any experimental work for some time. Starting in October with about ninety students in one way or another, he gave all the lectures and dealt with everything, examinations, marking papers etc. When in 1934 R. A. Buckingham was appointed as his assistant, Massey added another honours course and introduced a postgraduate course, choosing a new topic (or topics) each year, covering relativistic quantum theory of matter, quantum theory and chemistry, theory of atomic nuclei, mathematical biology and theory of metals during his stay at Queen's. Bates recalls that "Massey continued to do much of the undergraduate teaching himself. His superb lectures attracted students to mathematical physics. The ease with which he could master a subject did not lead him to expect too much of his classes. Massey had the uncommon knack of being able to stretch the brighter students by part of a lecture and yet not to lose the weaker students. He set numerous problems and wrote out solutions to them, which those who wished could consult the following week. His handwriting, then as later, was neat but tiny. Consequently it was not always easy to recognise the 12 squat letters (a, c, e, i, m, n, o, r, s, u, v, w): in his handwriting a word like 'recover' might have the semblance of being merely a sinuous line." Massey managed to maintain his research output. Having carried out his numerical work with a cylindrical slide rule and inadequate tables of functions, "he applied on March 20 1934 to the Royal Society for '£50 to be expended in paying an assistant to perform arithmetical calculations' on an investigation 'to determine how the internal (anomalous) nuclear field depends on the charge of the interacting particle, the experimental phenomena considered to include anomalous scattering of ???-particles, collisions of neutrons with nuclei and artificial disintegration by various nuclear projectiles.'... At his instigation Mr. John Wylie the Physics Workshop Superintendent, constructed a small scale differential analyser, the cost of the materials being borne by another grant of £50 (which Massey obtained from the Queen's Better Equipment Fund)". The differential analyser enabled the radial equation (with electron exchange) to be solved. Its output, in the form of a light pencil line drawn on graph paper, made it rather tiresome to use. However Massey and his associates made extensive use of it in calculations on, for example, the properties of helium at low temperatures and the photo-ionization cross-section of atomic oxygen. (Bates, op. cit.). In 1938 the first edition of his Negative Ions was published. His interest in this field was responsible for his start in 1937 in the well-known series of investigations on recombination in the ionosphere. In the middle of June, when the university year was over at Queen's, Massey took his wife and daughter to Cambridge in order to keep in touch with everybody at the Cavendish Laboratory until they dispersed for their own summer vacations, usually near the end of August.

Mathematics Department, U.C.L., 1938-39

Massey succeeded L. N. G. Filon F.R.S. as Goldsmid Professor of Applied Mathematics at U.C.L. in the autumn of 1938. At his invitation Buckingham, an Exhibition of 1851 Senior Scholar, accompanied him as did David Bates, a research student. The differential analyser was transferred to Gower Street, only to be destroyed in the war damage suffered by the College. It may be wondered why Massey moved to an applied mathematics chair, further away from experimental science. However it will be recalled that the department had assumed responsibility for the teaching of astronomy in 1865; moreover Filon's title included the Directorship of the Observatories, and there was a senior lectureship assigned to astronomy, held by C. C. L. Gregory, who also was Wilson Observer; and of course Filon, together with E. G. Coker, had pioneered the study of photoelasticity. Thus the department had been interested in experimental work and even had a small workshop, which Massey was able to build up after the war.

The War Years, 1939-45

In December 1939 Massey joined the Admiralty Research Laboratory at Teddington to work on the magnetic mine problem. During the previous September and October German aircraft had laid magnetic mines at harbour entrances causing the loss of nearly a dozen merchant ships. Defensive measures consisted of the degaussing of ships and sweeping the mines by various measures. In 1940 Massey was joined by Bates, Buckingham, Crick and J. C. Gunn. A happy event of that year was Massey's election as a Fellow of the Royal Society at the unusually early age of 32. He learnt of the good news in a note from C. G. Darwin, Director of the National Physical Laboratory, which adjoined A.R.L. The note in a grubby envelope, marked Confidential, was handed to him by a messenger as he left work for home on 29 February; apparently the formal election was to take place in a fortnight's time! By early 1941 the problems of defence against the German magnetic mines were largely resolved and Massey, with his team, moved to the Scientific Section of Mine Design Department (attached to H.M.S. Vernon) at West Leigh House, near Havant in Hampshire, Massey becoming Deputy Chief Scientist. J. C. (later Sir John) Gunn, who was Massey's closest associate from 1940 to 1943, has given an account of the contribution to the war effort made by Massey and his group during that period. "The first task was to perfect the British magnetic mine which used a robust but highly sensitive galvanometer as its triggering unit. Massey used the skills of his team in this programme. Bates worked on the design of packing to protect the units in the mine from the shock of aircraft drops. Buckingham and Gunn worked on the theoretical effectiveness of the mine, greatly helped by the knowledge of ship's fields gained at A.R.L. Crick was already devising alternative triggering circuits for the A.R.L. Experience had shown how rapidly a given weapon could be countered once its characteristics were established. Through the Admiralty Massey established contact with the Operations and Intelligence divisions concerned with mining and, in this way, information on German sweeping methods and convoy procedures was conveyed to West Leigh. The idea soon arose that variations in the circuitry of the British mine could be devised, aimed at particular enemy practice. What amounted to operational research was carried out on the selection of the best strategy. Ideas for tailor-made mines had to be converted into reality. These were required only in small numbers, and, in any case, the normal manufacturing process would have been much too slow. Massey succeeded in persuading the Admiralty to set up a small unit, code-named MX, for the production of these custom built mines. Crick was put in charge of the unit and, very quickly, it began successfully to produce mines aimed at such targets as sweepers or U-boats emerging from the Channel ports. MX was, undoubtedly, a great success for Massey's skill in breaking through the compartmentalization, which in deference to secrecy, was the usual pattern of weapon development. Work went on, involving many other members of Scientific Section on other types of non-contact mine - like the acoustic or the pressure mine. These all involved interesting problems of classical physics in which Massey was engaged. For example the pressure field of a ship posed mathematical problems very like those of the magnetic field. For a mine working on this field it was important to establish the background effect of ocean waves and this opened up a new area of study. Massey's period of service with the Admiralty came to an end in the summer of 1943 shortly after, on the retirement of A. B. Wood, he took over as Chief Scientist at West Leigh. In two years he had established a highly successful mining programme. He had also won from those who worked with him a respect and devotion that was to remain with them through subsequently very diverse careers." (B.B.D.)

After the Quebec Agreement of 19 August 1943 Massey was reluctantly released by the Admiralty to lead the theorists working at Berkeley, California, on the large-scale separation of U-235 from natural uranium by the electromagnetic method. The design of the plant had been finalized with the parameters optimized by empirical methods. Massey was in charge of a basic physics group set up to address the many problems that had been left unresolved. He was not confined to theoretical work and, having the use of the 37-inch cyclotron laboratory with all its resources of equipment and technical assistance at his disposal, in a remarkably short time, with the British group of scientists and technicians, he was able to accomplish much which, while of importance to the project, was of considerable interest for pure scientific work in the future. His later direction of experimental research as Quain professor benefited from this experience. Much of the work done by Massey's group at Berkeley is described in 'The characteristics of electrical discharges in magnetic fields' (eds A. Gunfire & R. K. Wakering). Professor David Bohm, a member of the group, has written: "Although it probably had very little affect on the goals of the Manhattan Project itself, the understanding that arouse out of our work proved of crucial importance in thermo-nuclear fusion. In particular our work disclosed that the plasma in the magnetic field has much more diffusion than one would expect. This diffusion is, indeed, one of the principal difficulties that got in the way of producing thermo-nuclear reaction in the magnetic field, as it caused ions to be lost to the containers of the plasma." (B.B.D.). Massey was one the six British scientists who met in Washington in 1944-45 to discuss the future organization of nuclear research in the U.K.

Mathematics Department, 1945-50

Soon after his return to the Mathematics department, Massey appointed E. H. S. Burhop, R. A. Buckingham, J. C. Gunn and D. R. Bates to the staff as lecturers. He obtained a grant allowing R. L. F. Boyd, an Imperial College graduate in electrical engineering, who had worked at West Leigh from 1943-46, and J. B. Hasted, an Oxford postgraduate whose training had been in physics with an orientation towards chemistry, to become research assistants working on experimental atomic physics. Burhop, who had first met Massey in Melbourne in 1928 when he stood in for the regular demonstrator to the first-year, practical physics class, and had joined Massey's group at Berkeley in May 1944, took a close interest in this work and at the same time began to use the nuclear emulsion technique to get back into research in nuclear physics. He was soon on very good terms with C. F. Powell, who had developed the technique in the first instant. Owing to the chronic shortage of space, experiments had to be set up in two small rooms and in a landing on a stairway. With Bates, Massey resumed their search for the mechanism of the loss of charged particles in the ionosphere. As Chairman of the Gassiot Committee of the Royal Society he instigated the first postwar international conference on the upper atmosphere. covering 'The emission spectra of the night sky and aurorae'. He also returned to problems of non-relativistic collision theory, and the theory of nuclear forces, and he completed the 388-page, second edition of the 'Theory of Atomic Collisions'. It was during this period that he became particularly interested in the teaching of mathematics to physics and chemistry students; this resulted in the publication of the comprehensive textbook, 'Ancillary Mathematics', with H. Kestelman, in 1959. With Burhop, he prepared the work on the physics of electronic and ionic collisions, which on publication in 1952, as Electronic and Ionic Impact Phenomena, helped to rekindle the interest in those topics and stimulate the postwar growth of work in the field. Although very busy, as always his readiness to help a friend or colleague is illustrated by Crick, who has written appreciatively: "Massey helped me after the war. When I told him I wanted to go into biology at the molecular level, he introduced me to Maurice Wilkins, whom he had known at Berkeley and also, with his blessing to A. V. Hill, who in turn persuaded the Medical Research Council to support me." (B.B.D.).

Massey was the unanimous choice to succeed Andrade in the Quain chair. Before accepting the offer, he satisfied himself on two counts, namely the possibility of co-operation with A.E.R.E., Harwell, whose Director was Sir John Cockcroft, involving its accelerator facilities, and the recruitment of H. S. Tomlinson to develop the technical services and to look after the equipment and use of the research space to be provided in the New Block, the first stage of the College's plan for development of the department. Tomlinson had worked with him and Burhop at Berkeley and was then at A.E.R.E., Harwell. To avoid any problems with the existing senior technical staff, a position of the right seniority for Tomlinson was found by the creation of a new post on the academic staff with the title of Assistant. Burhop, Buckingham and Bates came over with Massey as Readers, Burhop filling the established readership vacated by King, and two more established readerships being created for the other two. Gunn had resigned from the Mathematics department in February 1948 on his appointment as Professor of Theoretical Physics at Glasgow University. L. Castillejo, T. C. Griffith, and M. J. Seaton became Assistant Lecturers, Castillejo and Seaton having been research students, and Griffith an experimental assistant in the Mathematics department; incidentally Seaton having served as a navigator in the Pathfinder Force of Bomber Command, joined the Physics Department in 1946, graduated with first-class honours in 1948, only to transfer to the Mathematics Department as a postgraduate student working on certain reaction rates applicable to astrophysical and geophysical problems under Bates. Another appointment as Assistant Lecturer was F. F. Heymann, a South African electrical engineer, who had been working on the development of an experimental 22 MeV Betatron at Metropolitan-Vickers Electrical Co. Ltd., Manchester. Boyd and Hasted having been awarded I.C.I. Fellowships, transferred to the department in these roles, and M. J. Bernal and P. Swan were appointed as D.S.I.R. research assistants to Massey. Two of the research students changing departments were A. Dalgarno and B. L. Moiseiwitsch, who were completing their Ph. D. courses. Mr. J. Baserga, who had run the workshop in the Mathematics Department, also came over to set up another workshop in the Department. Massey's friendly reception of the old departmental staff can be illustrated by the author's experience; having received an invitation to go to the R. I. with Andrade, financed by the British Rayon Research Association, Massey made it quite clear that he would welcome his staying on in the department.

Massey and his accompanying staff soon settled down in the makeshift accommodation of the department. A vigorous programme was initiated of theoretical and experimental research on many aspects of the physics of collisions both at low and high energies. This involved collision processes in gas discharges, slow collisions of atoms and ions, basic optical excitation processes, and the measurement of concentrations of atomic hydrogen by micro-calorimetry with the view to its application in the determination of cross-sections operative in certain electron-atom collisions. A 20 MeV electron synchrotron was generously loaned by Sir John Crockcroft and erected in the department. Construction began on a 4.5 MeV microton, two high-pressure cloud chambers to operate at 100 atm., and a magnetic lens to focus electrons of energy up to 4 MeV. In the first session there was a marked increase in the number of postgraduate students, there being 29 reading for higher degrees. Special lecture courses for these students were given in radiation theory, theory of spectra, nuclear physics, and atomic collision phenomena. In addition seminars in nuclear physics, and electronic and ionic physics were held regularly throughout the session. A very successful conference on the Dynamics of Ionized Media was held in the department during March, it being attended by 100 people from England and the Continent. Massey gave three lectures per week throughout the session on modern physics to the third-year students and several members of the old departmental staff, including the author, attended them. An alternative Part II course on Mathematical Physics was introduced and students opting for this course sat a Part II special, six-hour, theoretical problem paper. In addition to Massey's lectures, third-year students attended three lectures per week on selected topics in either experimental or mathematical physics according to their specialized Part II option. David Bates resigned at the end of the session on his appointment to the Chair of Applied Mathematics in Queen's University, Belfast. 1951-52 saw progress on all fronts; the laboratory was chosen as one of the four to receive support from the Warren Research Fund of the Royal Society in connection with research in the physics of electrical discharges; and a special meeting of the Physical Society on nuclear physics was held in the large theatre, all the papers being contributed by members of the department.

The 1952-57 quinquennium saw the start of work, in collaboration with Dr. G. R. Evans of the University of Edinburgh, on the nature of particles produced by cosmic rays interacting in the earth's atmosphere, observations being taken in a high-pressure cloud chamber on Mt. Marmolada in the Dolomites: grants to assist this work were made by the D.S.I.R. and the Central London Research Fund. Progress in ionic physics was reported at a three-day conference, held in the department in April 1953, for the university physics teams, whose research in this field was financed by the Warren Research Fund. May 1953 brought the offer of rockets from the Ministry of Supply for scientific research, and in June 1953 the deuterium filled, high-pressure cloud chamber was operated continuously in connection with the 150 Mev proton source available from the A.E.R.E., Harwell synchrotron. The new Physics Wing, the first stage in the provision of permanent facilities for the department, was occupied before the end of the 1953-54 session, and despite the disorganization associated with the transfer of complicated apparatus from one site to another, research continued to develop on existing lines. A grant was made by the U. G. C. for Dr. A. D. Booth of Birkbeck College to make a copy of his electronic computer for installation in the department.

On 4 May 1955 the formal opening of the new Wing by Sir James Chadwick took place in the presence of some 450 guests from industrial firms, scientific institutions, colleges and schools. The guests were received by the Provost, and, after tea in the Housman and Haldane Rooms, Sir James delivered an address in the North Cloisters. They were conducted in parties round the new wing during the course of the afternoon and evening. To mark the occasion, there appeared, in Nature, Vol. 175, p. 1069, 1955, a description of the new Wing, including its facilities for teaching and research, and some account of the research being carried out in the department. The Wing, which had six floors, was designed by Prof. A. E. Richardson and built by Messrs. Dove Bros. Ltd. Three of the six floors were devoted to teaching laboratories, each of which occupied a floor space of 4,600 sq. ft., containing some sixty or seventy student benches and including dark rooms for optical experiments, apparatus stores and technicians' rooms; in addition there were photographic dark rooms, a balance room, and workshop facilities for undergraduate use. The research facilities were housed on the lower ground, the ground and fourth floors. The lower ground floor had a ceiling 16.5 ft. high, the greater part of the floor being occupied by the electron accelerator laboratory, which extended along the whole length of the floor and over about two-thirds of the width. An overhead travelling crane ran the full length of the laboratory. This floor also housed a store, glass-blowing shop, dark rooms, a spectroscopy laboratory, and a room for storing and handling small quantities of radioactive isotopes. The ground floor contained a number of staff rooms and offices, but research laboratories comprised its greater part. The top floor contained rooms for staff and for research students working in theoretical physics, the departmental library, the computing laboratory, and a small lecture theatre.

During the 1955-56 session the development of instruments for use in rockets for upper atmospheric research proceeded intensively and preliminary launching trials were carried out at the artillery range at Shoeburyness. The bubble chamber group took off after Cyril Dodd returned from his five-month visit to leading U.S.A. laboratories working in the field. A new project involving co-operation with the University of Bristol was the study of nuclear emulsions exposed to the meson beam from the Bevatron at Berkeley, California. The Booth computer was installed in the department and operated to good effect. W. E. Duncanson left in 1956 to become Principal of the Kumasi College of Technology in the Gold Coast.

The 1957-62 quinquennium saw the department participating in a special Royal Society soiree to celebrate the opening of the International Geophysical Year, 1957-58, by exhibiting instruments for use in the programme of upper atmospheric research and demonstrating the techniques. Arrangements were made for a collaboration between A.E.R.E., Harwell and the department to send a joint team to C.E.R.N., Geneva to work on two experiments involving the first C.E.R.N. accelerator, the 600 MeV synchrocyclotron. This enabled departmental staff to participate in experimental work overseas in addition to carrying out their share of undergraduate teaching. A large D.S.I.R. grant of £22,000 for three years from August 1957 allowed the recruitment of technical staff and a research assistant, who were able to be based at C.E.R.N. "This, together with the developments in Space Research, was the beginning of the era of 'big physics' at U.C.L. The pattern of research became atomic and theoretical physics 'in house' and space research and high-energy physics split between planning, instrument development and data analysis at home, and experiments carried out with major facilities outside the college, largely abroad." (B.B.D.). The first experiments in the programme of upper atmospheric research, using equipment in the Ministry of Supply's rocket, 'Skylark', were carried out at Woomera, Australia, in November 1957. The College allowed staff to be absent on projects in term time provided satisfactory arrangements were made for their teaching duties. In fact Massey had an arrangement with the Provost, Sir Ifor Evans, that certain areas of the world were designated as parts of the College so that staff going there for their research were not regarded as requiring leave. A new microton started to operate, providing electrons of energy 28 MeV, and a 500 keV van der Graaf accelerator was largely constructed and awaiting installation in the new laboratories to be provided in the former Seamen's Hospital at 25 Gordon Street. Plans were made to work on the 50 Mev proton linear accelerator, which was destined to be the first piece of equipment operated by the new National Institute for Research in Nuclear Science. 1958 saw the award of Royal Medal of the Royal Society to Massey to accompany the Hughes Medal awarded to him in 1955. In 1959 the conversion of the Seamen's Hospital was completed, providing sufficient accommodation for the department to relinquish most of its territory in the central block of the College; this year also saw the start of a major design study of a large propane bubble chamber with N.I.R.N.S. support, the engineering team being led by Tomlinson and the physicists by Henderson. In 1957 R. A. Buckingham was made Director of the University of London Computational Unit; and L. Castillejo joined Prof. R. E. Peierls in the Theoretical Physics Department at Birmingham University, being replaced by S. Zienau, formerly an honorary research assistant. 1960 saw Massey created a Knight Bachelor in the Queen's Birthday Honours. A second chair of physics was established in that year and filled by a former Queen's University student of Massey's, namely J. Hamilton, an expert in theoretical high-energy physics, and at the same time the title of professor was conferred on Eric Burhop.

In 1962 planning began on an extension of the Physics Wing, the second stage of the building programme envisaged for the department in the College rebuilding plans. D. G. Davis, an old student, who had been appointed in 1960 as a lecturer with special responsibilities for administration instead of teaching, was concerned with the detailed plans. On asking Massey how he wanted the planning carried out, he recalls Massey remarking "that all the postwar developments of the department could not have been forseen more than a couple of years before they occurred and that the prime requirement of the new building was flexibility". No big research laboratory was required, since large equipment would be used in shared national or international centres. A 'loose-fit' philosophy was to be adopted, with laboratories planned roughly right for a variety of possible users, a well equipped workshop forming a central part of the development. "Massey's approach to the building was like his organization of the Department essentially pragmatic. There was no grand plan, rather a series of steps building on existing strengths, with a bias towards the more fundamental, and a strong technical base for development of new experimental techniques". (B.B.D.).

On 26 April 1962 the first British satellite, named Ariel 1 on its establishment in orbit, was launched by a Thor-Delta rocket from Cape Canaveral; five of the seven experiments aboard were the responsibility of the U.C.L. group, four being successful and continuing to provide results up to November 1964. A discussion meeting on the results then obtained was held at the Royal Society on 2 and 3 May 1963 under Massey's chairmanship. There being no opportunity to expand its space research on the College rectangle, the department sought external benefactions for the provision of an additional laboratory outside London. The Mullard Company made provision for a gift of £65,000 in 1964 and this accounted for some three-quarters of the cost of buying and adapting Holmbury House, a country mansion at Holmbury St. Mary, near Dorking. About one-fifth of the academic staff of the department, together with their technical support staff, equipment, etc., was moved to the so-called Mullard Space Science Laboratory (M.S.S.L.), which came into full use in October 1966 and was formally opened on 3 May 1967 under Boyd's directorship. The group, the largest space science research group in Britain, had embarked on a major programme involving experiments on eight satellites and over thirty sounding rockets, the main fields of investigation being in ultra-violet and X-ray astronomy of the sun and other celestial objects, and the study of the ionosphere, the magnetoshere and the interplanetary medium.

Burhop spent the 1962-63 session at C.E.R.N., serving as secretary of the Amaldi Committee appointed to study and report on the future policy for accelerators in Europe. Its report was adopted by the European Committee for Future Accelerators as providing the policy for accelerator developments during the next 15 years; both the recommended machines, the Intersecting Storage Rings and the Super Proton Synchrotron, were subsequently built and formed the backbone of high energy physics in Europe until the eighties. In 1963 he was elected to the Fellowship of the Royal Society for his work in atomic and particle physics. It was in that year that he proposed that by combining spark chamber and emulsion techniques it would be possible to locate rare neutrino interactions in an emulsion enabling very short-lived particles to be detected. The U.C.L. Spark Chamber and Emulsion Groups were involved in establishing the viability of the method in 1964. However it aroused little interest for almost ten years until the discovery of weak neutral currents and the possibility of unified theories gave a renewed impetus to the search for new quark flavours, in particular, charm. As a consequence Burhop and others suggested the experiment, E247, which was supported by the Director of Fermilab and ran during 1975-76 in the wide band neutrino beam there, successfully locating 37 neutrino interactions in emulsion, from one of which a very good candidate for a charged charmed particle was seen to emerge.

The academic staff numbered 28 at the start of the 1962-63 session; there were 3 Professors, Massey, Burhop and Hamilton; 7 Readers, Gibbs, Boyd, G. B. Brown, Dodd, Hasted, Heymann and Seaton; 2 Senior Lecturers, R. C. Brown and Jennings; 15 lecturers, Aitken, Davis, M. J. B. Duff, Fox, Gilbody, Griffith, Groves, Heddle, Henderson, Heyland, Rand, Stannard, Willmore, Zienau and P. W. Roberts, an old student, who was also the College Adviser on Protection against Radiation Hazards; and 1 Assistant, Tomlinson. The Calendar for the 1962-63 Session also listed on the research side 12 Temporary Research Assistants, 5 Honorary Research Associates and 19 Honorary Research Assistants. Senior promotions soon followed, namely, Boyd and Seaton, Professors by conferment of title in 1963; Groves and Willmore, established Readerships, Heddle, Henderson and Jennings, Readerships by conferment of title in 1964; and Griffith and Zienau, Readerships by conferment of title in 1965. In October 1965 R. F. Stebbings returned from America to fill an established readership specially created for someone of experience and distinction in the field of experimental physics. Hamilton left in 1964 for a Professorship at the Nordic Institute for Theoretical Physics, Copenhagen, and Heddle went to a Readership at the new University of York. Castillejo returned from Oxford (where he had gone with Peierls in 1963) in January 1967 to fill the established Chair, which had remained vacant since Hamilton's departure. Meanwhile Heymann had been appointed Professor by conferment of title. The first appointments of Visiting Professors to the College was made in the 1967-68 session to establish a close academic association with persons of distinction working in research institutions and elsewhere outside the College. Dr. J. A. Saxton, Director of the Radio and Space Research Station, S.R.C., Slough, became the first such Professor in the Department. 1967 saw the election of Seaton to the Fellowship of the Royal Society for his contributions to atomic physics and astrophysics, and the departure of Henderson for a Senior Lectureship in the Department of Natural Philosophy, University of Aberdeen; in 1968 Hasted took up the Chair of Experimental Physics and the Headship of the Department at Birkbeck College, but retained his leadership of that part of his Ionic and Electronic Physics Research Group remaining behind; and Willmore and Groves were appointed Professors by conferment of title in 1968 and 1969 respectively. Boyd was made a Fellow of the Royal Society in 1969 for his contributions to ionospheric physics, and X-ray and ultra-violet astronomy, and to the exploitation of space science techniques in these fields. Then in 1972 both D. H. Davis and A. C. H. Smith were appointed Readers by conferment of title.

After the acceptance of the Robbins Report by the Government in late 1963, some expansion of the Department was planned to increase the maximum intake of undergraduates from 48 to 60 and the academic staff was increased by four lecturers. The first Departmental Tutor was appointed in 1963, Dodd assuming that office. In January 1965 the Secretary of State for Education and Science set up a Council for Science Policy, with Massey as Chairman, to advise him on the exercise of his responsibilities for civil science policy.

Gibbs retired at the end of September 1965, fifty years after his entry to the College as a potential engineer; he transferred to physics one year later. His studies were interrupted in May 1917 when he went to the Admiralty Experimental Station at Harwich to work on anti-submarine measures with Rankine and Bragg. Returning to the College in the second term of the 1918-19 session, he graduated with first-class honours in 1920, and was awarded the M.Sc. degree in 1923 for his research work. When Sir William Bragg went to the Royal Institution in 1923, Gibbs and other members of his research team accompanied him. Gibbs worked on X-ray crystallography, carrying out an investigation of the lower members of the fatty acid series, and becoming an authority on the structure and properties of quartz. He returned to College as a Research Assistant in 1927, became a Lecturer in 1931, and a Reader in 1936. From 1939-45 he worked at the Royal Aircraft Establishment, Farnborough, one project involving collaboration with Uffa Fox on the airborne lifeboat. He was responsible for Harold Billet joining the College after the war, Billet later becoming Professor of Mechanical Engineering, Vice-Provost, and then Acting Provost in the 1978-79 session between the departure of Lord Annan and the arrival of Sir James Lighthill. Gibbs was Acting Head of the Department during the second and third terms of 1950; then from 1950-65 he was in charge of the undergraduate laboratories, formerly as Superintendent and latterly as Deputy Director. During this period he lectured on modern physics to the second-year special physics students. In 1952 he succeeded Orson Wood as Sub-Dean of the Faculty of Science and Tutor to Science Students, carrying out those arduous duties for thirteen years with his characteristic quiet efficiency, giving his time and attention unsparingly to a countless number of students, many of whom remember his help most gratefully. He served on the Professorial Board from 1935-39 and 1957-65, and on the College Committee from 1949-54. At the University his services included membership of the Senate, Academic Council, Finance and General Purposes Committee, Vice-Deanship of the Faculty of Science, and Chairmanship of the Board of Studies in Physics. He was made a Fellow of the College in 1962. Gibbs was succeeded by Dodd as Sub-Dean and Faculty Tutor, the author taking over the Departmental Tutorship. G. B. Brown retired at the end of September, 1966, having been a member of the Department for forty years. He joined the Department as an Assistant, having graduated at Manchester University in 1924, and worked as a Research Assistant to Professor W. L. Bragg on the structure of certain silicates, gaining the M.Sc. degree in 1925. He became a Lecturer in 1931 and Reader in 1946. His fine experimental work in acoustics on sensitive flames and edge tones received general recognition, being extensively cited in modern text books, e.g., Acoustics by Alexander Wood. His book on "Science; its Method and its Philosophy", published by Allen and Unwin in 1950, and his later writings on the historical and philosophical aspects of science attracted considerable interest. 'G. B.' gave regular courses of lectures to general and special students, in particular the special lectures on classical electricity and magnetism, and finally those on properties of matter; he regularly demonstrated in the undergraduate laboratories. In 1982 he had published his "Retarded Action-at-a-Distance: The Change of Force with Motion" by Cortney Publications Luton.

The following year saw the retirements of E. C. Rowe and R. J. Fisher. Rowe joined the department in April 1922 to take over Byron's duties in the laboratories, having previously spent five years in the instrument shop of Johnson and Phillips and three years with the Dictograph Telephone Co. In 1935 he was awarded the Diploma in Laboratory Arts, then introduced by the Institute of Physics, and in 1947 he became a Founder Member of the Institute of Science Technology. Rowe's work during the Bangor evacuation, including the establishment of the laboratory in the High Street, has been described earlier; however reference is again made to the photograph of him standing at the door of his partitioned room in the corner of that laboratory, (H. & N. 349:188). He became a Chief Technician in 1950 and a Principal Technician in 1960. When the College decided in 1962 that one senior member of the laboratory staff in each department should be appointed as Head, Rowe became the first Laboratory Superintendent in the Department. Countless students remember gratefully the help given to them in the laboratory by Ted Rowe.

Fisher joined the workshop of the department in October 1923, filling a vacancy left when Jenkinson went to the R. I. with Sir William Bragg. He served under W. Fox, who succeeded Jenkinson as Chief Mechanic in May 1924, until Fox's retirement in July, 1937; and under E. J. Faulkener, Fox's successor, from September 1937 until 1957, with the exception of the war years, when both of them were seconded to the Ministry of Supply Inspectorate. In 1957 Fisher succeeded Faulkener as Technical Officer in charge of the large workshop, then housed in the old basement laboratory, employing some dozen skilled technicians engaged on the construction of apparatus and instruments required by the research groups working in atomic, nuclear and space physics. Fisher was a skilled craftsman and he took a great interest in the work of the Physical Society to encourage apprentice instrument makers, becoming the Senior Judge in the Class 1 (Instrument) competition held for them at the time of the Annual Exhibition. His long distinguished service was greatly valued by the department. Fisher was succeeded by J. E. Pitcher from A. W. R. E., Aldermaston, who was responsible for equipment of the new workshop housed in the old electron accelerator laboratory.

In 1966 the University introduced a new B.Sc. degree structure enabling certain Colleges of the University to offer College-based courses extending over three years. This was particularly welcomed by the Biological Science Departments since it enabled their students to select suitable combinations of courses and to defer their choice of specialist subject or combination of subjects until the end of their first year of study. The Department rather reluctantly had to adopt the course-unit system, but insisted upon its main-stream physics students following a common course structure directed towards their becoming professional physicists. The introduction of the new structure made heavy demands on the Faculty with the result of Dodd becoming employed full-time therein. Burhop assumed his three-year Deanship of the Faculty in 1967, so the Department played a prominent part in the administration of the new-degree structure. A new joint degree course in Chemistry and Physics was introduced in 1969 for a small entry of well qualified candidates and this was followed by the introduction of an Applied Physics degree course in 1970.

In the mid-sixties Massey realised that developments in the manufacture of plastic film for balloons were making it possible to carry instruments to altitudes where the absorbing effect of water vapour was negligible. Thus in 1966 he started an Infra-Red Astronomy Group to make observations in the far infra-red, the only part of the spectrum in which modern astronomical observations were not being made. Jennings and Aitken were turning their interests from high-energy physics towards infra-red astronomy, and Tomlinson and some of his bubble chamber design team were becoming available for a new project - a stabilized balloon-borne gondola carrying a 40cm. telescope, which was first flown at Mildura, Australia in 1970; hence it was a propitious time for the formation of the new group. Towards the end of the decade there was another development in astronomy, this time in the optical region, when Boksenberg conceived a new approach to astronomical detection, namely, the Image Photon Counting System for the observation of very faint extragalactic objects; this was developed with S.R.C. funding and used on the Palomar 200-inch telescope with great success towards the end of 1973.

In 1967 Burhop had taken over the leadership of the Bubble Chamber Group and soon realized the advantage of large heavy liquid chambers in studying neutrino interactions. He directed the activities of the Group towards participation in a research programme set up in conjunction with a number of European Bubble Chamber Laboratories using the Gargamelle Chamber at C.E.R.N. This proved very successful establishing in particular the existence of weak neutral currents which was of great significance for the development of unified electromagnetic and weak interactions.

Massey had an abiding interest in positrons and positronium and for some years had been anxious to develop an experimental programme on positrons in gases. Following his attendance at the first conference on positron annihilation, organized by Stewart and Roellig at Detroit in July 1965, he began to look around for colleagues to realise his objective. The experimental research programme involving the 50 MeV Proton Linear Accelerator at Harwell with measurements of the polarization parameters in double and triple scattering of nucleons by protons was being completed. This, together with the availability of radioactive positron sources, led Massey to suggest to Griffith that he should turn his attention to experiments with slow positrons. Moreover he persuaded Heyland, an electronics expert, who had devoted his time in running the third-year undergraduate laboratory, to join Griffith in forming the Positron Physics Group in 1968. The Group got off to a good start with Roellig spending a sabbatical year with it and Canter, who had worked with Roellig on positron annihilation in helium at low temperatures, joining it the following year.

To mark Massey's 60th birthday in 1968 some 120 of his friends, colleagues and former students contributed to the commissioning of his portrait by Claude Rogers, and some 20 of them also contributed to a Festschrift volume of 'Advances in Atomic and Molecular Physics', and donated the royalties to the portrait fund. The presentation of the portrait to Sir Harrie by Prof. P. M. S. Blackett, P.R.S. was witnessed by some 160 diners assembled on 3 December 1968 for the Physics Department Dinner, presided over by the Provost, Lord Annan. In 1969 Massey's term of office as Chairman of the Council for Science Policy ceased, but he took on new responsibilities, namely Physical Secretary and Vice-President of the Royal Society, and Vice-Provost of the College, and in 1970 he became the Royal Society assessor on both the Astronomy and Space Policy and Grants Committees of the S.R.C. Astronomy, Space and Radio Board.

At the beginning of the quinquennium in 1962 ten former D.S.I.R. supported research projects, mainly in atomic and nuclear physics, were taken over by the University Grants Committee, an earmarked sum of £30,555 p.a. being added by the U.G.C. to the University Court grant to the College in the financial year 1962/63 for that purpose. In August 1967 the earmarking ceased and was assimilated into the normal College budget at the rate of £47,500 p.a., providing posts for 22 of the research staff involved, 10 being tenured lectureships; there was also approximately half the cost of another lectureship, and £5000 was added to the departmental grant. In 1967 a second transfer of support for research work from the Research Councils to the U.G.C. was agreed; this time the arrangements were very closely scrutinised by all parties as the Treasury insisted on reducing the budgets of the Research Councils by exactly the amount by which the U.G.C. budget was increased. Four of the department's big science programmes were taken over, two in high energy physics and two in space research; the transfer funds were again earmarked for the five years of the quinquennium, 1967-72, after which they were to be assimilated in the normal College block grant of U.G.C. support from the University Court. In August 1972 the assimilation provided for 38 posts, including 8 lectureships, with £20,562 added to the departmental grant, at a cost of £106,000 p.a.

The Department suffered a great loss in the death of Harry Tomlinson on 5 February 1971; the College Report for 1970-71 described him as "one of the most effective and original designers of scientific instruments in the country" and acknowledged "the outstanding value of his work in the Department". It recalled that "For a number of years he was fully engaged in the development by the Department of a Heavy Liquid Bubble Chamber for the National Institute for Research in Nuclear Science. Recently he had been responsible for the design and construction of a controllable telescope to be carried on balloons for infra-red astronomy". The Department issued its own Harry Tomlinson obituary booklet, with contributions from Massey, Towlson and Venis, covering the man and his work for the Department on Cloud Chambers, The Bubble Chamber and Balloon Platforms.

August 1972 saw the resignation of Willmore to take up the Chair and the Headship of Space Research in the University of Birmingham. After rejoining the Department from A.E.R.E., Harwell in 1957, he played a prominent part in the space science programme, becoming deputy leader of the largest research group in the Department. The Copernicus satellite, launched on 27 August 1972, four days before Willmore's departure, carried the group's grazing incidence parabolic reflectors, with proportional counters at the foci, as an auxiliary experiment to the main ultra-violet observing system. The design of the system had been undertaken before the existence of observable cosmic X-ray sources had been established and the proposal to include it in the payload of this, the third U.S. orbiting, satellite had been accepted in 1963. By good fortune the long delay of the launch of the satellite took place at a most opportune time, as will be made clear later.

In the 1967-72 quinquennium the U.G.C. for the first time had asked the College specifically to spend extra in certain indicated areas, of which physics was one. However the quinquennial grant, finally announced in January 1968, was too small even to cover existing commitments. It heralded a gloomy policy of general economy, the College being forced carefully to scrutinise all its expenditure. In October 1969 the Provost, Lord Annan, actually wrote to Massey about the possibility of achieving a 6% reduction in staff numbers and in July 1971 he met the Professors of Physics and Chemistry to explain why enquiry should be made into the expenditures of two of the largest and most expensive departments in College. Then in 1973 five Committees were set up to look into the level of resources of these two Departments, the School of Environmental Studies, the Slade School, and the Library.

A Department of Astronomy was formed in College in 1951 when C. W. Allen was appointed to the newly-created Perren Chair of Astronomy, provided by an endowment under the will of Mr. F. Perren. The Court of the University having decided that responsibility for the direction of the University Observatory at Mill Hill should be transferred to the College from 1st. August 1951, the new Professor also became Director of the Observatory, and responsibility for the Observatory was formally transferred to the College at the beginning of the 1952-57 quinquennium. Previously Allen had been the Principal Assistant at the Commonwealth Observatory, Canberra (now the Mount Stromlo Observatory). At College he began the task of building up a first degree course in Astronomy - at that time the only one in England and Wales. Allen played a leading part in British astronomy and continued his researches in solar and laboratory astrophysics. His best known work was his volume of critical astrophysical data, 'Astrophysical Quantities', first published in 1955 and about to appear in a third edition on his retirement in 1972.

In the summer of 1972 the Committee appointed by the Professorial Board to consider the steps to be taken on the retirement of Professor Allen reported and recommended that the two Departments of Physics and Astronomy be amalgamated from 1 October 1972; the Perren Chair be filled; and Professor Sir Harrie Massey be Head of the combined Department. Dr. R. Wilson, formerly Head of the Astrophysical Research Unit of the Science Research Council, Culham, was appointed Perren Professor of Astronomy and Director of the Observatory; he joined the new Department in January 1973, the old Astronomy academic staff - Drs. D. McNally (Assistant Director of the Observatory), W. B. Somerville (Tutor to Astronomy Students), J. E. Guest and D. R. Fawell, and Mr. E. W. Foster - having transferred in the previous October. Wilson was well known in the old department from the early sixties onwards firstly through his involvement in a programme of ultra-violet spectroscopy of the solar corona and the stars by rocket-bourne equipment, and then in the development of satellite ultra-violet astronomy, leading up to the realisation of the International Ultra-Violet Explorer satellite (I.U.E.). He had been the second Visiting Professor appointed in 1968.

The amalgamation of the two departments was very timely and even necessary in that Wilson was only prepared to accept the Perren chair on that basis; moreover it was fortunate to have occurred under the wise leadership of Massey. On the research side it brought together active groups in X-ray, ultra-violet, optical and infra-red astronomy, as well as in astrophysics and geophysics. On the teaching side it brought welcome relief to the management of the astronomy undergraduate entry which had leapt from 9 in 1969 to 23 in 1970 and was to reach 30 in 1975 owing to the popularity of the subject generated by the space programme.

R. C. Brown retired in 1973 having served the College for forty-seven years. He joined the Department of Physics as a Demonstrator in 1926, became an Assistant in 1928, a Lecturer in 1930 and a Senior Lecturer in 1945; in 1961 he succeeded Orson Wood as Careers Adviser, retaining his Senior Lectureship on a part-time basis. 'R. C'. was a valuable member of the department, being a very good teacher both in the lecture theatre and the laboratory. For many years he taught physics to 1st M. B. students and properties of matter at all levels; latterly he taught optics. His research was in the field of surface tension and he was an acknowledged authority on the subject. He wrote an excellent text-book of physics for Intermediate and 1st. M. B. (later A-level) students, and served as a Chief Examiner and Moderator for Advanced and Scholarship Level Physics for the London Board. He also served as Secretary of the Board of Studies in Physics. In College his membership of Committees included the Vice-Chairmanship of the Student Health Association Committee. His work as Careers Adviser extended over a period of rapid growth in student numbers and of incredible complications in the employment situation. Successive generations of students have had cause to be grateful to him for his humanity and understanding and for the range of knowledge and experience he brought to their careers problems. Departmental Tutors were also grateful to him for the confidential notes on their third-year students which he issued to them.

E. W. Foster also retired in 1973, having joined the Department of Astronomy in 1953 after various research appointments elsewhere. His experience and high standards in spectroscopy and experimental physics enabled him to make considerable contributions to the measurement of fundamental spectroscopic quantities of astrophysical importance. His teaching in astrophysics and molecular spectroscopy was greatly valued.

The titles of Reader were conferred on Wilkin and Bullock in 1973 and 1974 respectively. On 30 September 1974 the first students were admitted for the new joint Astronomy and Physics degree. In 1975 Wilson was elected to the Fellowship of the Royal Society for his contributions to solar and general astronomy in the ultra-violet through the use of space vehicles.

C. A. R. Tayler retired at the end of July 1975, having joined the Department of Physics direct from school on 9 March 1925. On Friday, 7 March 1975, Massey had a luncheon party in the Whistler Room to mark the fiftieth anniversary of Tayler's appointment; Gibbs, R. C. Brown, and Brinsden from Botany (and Microbiology) also attended the luncheon. After some experience in the teaching and research laboratories, Tayler became Lecture Assistant in 1929; 1953 saw him assume the new grade of Senior Technician, with two assistants, and in 1958 he was promoted to become Chief Technician. When Rowe retired he was made Laboratory Superintendent, still being based in the theatres, but with many additional duties and responsibilities. In 1935 he was awarded the Institute of Physics Diploma in Laboratory Arts and in 1960 he was elected to the Fellowship of the Institute of Science Technology, becoming a Council Member for the next three years. Tayler was a skilled glass blower and an expert photographer, and was always ready to help members of staff or research student; his preparation of, and help with, lecture demonstrations were invaluable.

October 1974 was a significant month for the department. A new half course-unit structure for the degree courses offering greater flexibility was introduced. Massey started his last series of lectures, giving the ¹/₂ c.u. on Modern Physics and Astronomy to the Astronomy and joint Astronomy and Physics students, and Wilson started his first series, giving the ¹/₂ c.u. on Foundations of Modern Astronomy to the same students. The fifth U.K. satellite, the first to carry a cosmic X-ray scientific payload, was launched on 15 October 1974 as Ariel 5. It carried two M.S.S.L. instruments, a rotation collimator for the accurate positing of new sources and a multi-anode gas proportional counter for X-ray spectral measurements.

The 1974-75 Calendar listed the academic staff of the new department as follows:- Sir Harrie Massey, Quain Professor of Physics and Director of Laboratories; R. Wilson, Perren Professor of Astronomy; R. L. F. Boyd, E. H. S. Burhop, L. Castillejo, G. V. Groves, F. F. Heymann and M. J. Seaton, Professors of Physics; L. R. B. Elton, M. O. Robins and J. A. Saxton, Visiting Professors; F. W. Bullock, D. H. Davis, C. Dodd, T. C. Griffith, R. E. Jennings, A. C. H. Smith, C. Wilkin and S. Zienau, Readers in Physics; J. W. Fox, Senior Lecturer and Tutor; D. McNally, Senior Lecturer and Assistant Director of Observatory; D. G. Davis, E. B. Dorling and M. J. Esten, Senior Lecturers; W. B. Somerville, Lecturer and Tutor to Astronomy Students; J. McKenzie, Lecturer and Tutor to Physics students; D. K. Aitken, J. H. Bartley, A. Boksenberg, P. J. Bowen, J. A. Bowles, S. J. B. Corrigan, J. L. Culhane, B. G. Duff, M. J. B. Duff, M. M. Dworetsky, D. R. Fawell, W. M. Glencross, J. E. Guest, G. R. Heyland, J. W. Humberston, D. C. Imrie, T. W. Jones, G. J. Lush, B. R. C. Martin, A. J. Metheringham, D. J. Miller, D. L. Moores, W. R. Newell, K. Norman, J. H. Parkinson, T. J. Patrick, Gillian Peach, W. J. Raitt, D. Rees, P. W. Sandford, S. J. Sharrock, W. A. Towlson, T. E. Venis, D. A. Wray and G. L. Wrenn, Lecturers; P. W. Roberts, Lecturer and Adviser on Protection against Radiation Hazards; A. F. D. Scott, J. J. Todd and D. N. Tovee, Research Assistants; S. M. Fisher, Demonstrator; R. F. Berthelsdorf, P. J. N. Davison, A. D. Johnstone, A. C. Newton, F. D. Rosenberg and P. H. Sheather, Associate Research Fellows; K. G. R. Allen, W. Allison, K. Birkinshaw, J. C. Blades, D. J. Carnochan, D. H. Clark, C. I. Coleman, P. G. Coleman, A. M. Cruise, J. S. Dolby, I. Furniss, F. J. Hawkins, J. C. Ives, Barbara Jones, B. Kirkham, A. R. Malvern, Helen Mason, S. D. Pepper, M. K. Pidcock, C. G. Rapley, M.Salem, I. R. Tuohy, D. M. Watson and J. Zarnecki, Associate Research Assistants; A. H. Gabriel, Carole Jordan, R. P. W. McWhirter, H. Rishbeth and L. Thomas, Hon. Lecturers; Prof. P. H. Bodenheimer, Prof. R. A. Buckingham, J.-F. Germond, Prof. J. B. Hasted, D. G. Obsorne and Prof. F. R. Stannard, Hon. Research Fellows; J. D. Argyros, D. C. Black, J. A. R. Dubau, A. G. Michette, Hon. Research Assistants - a total of 111, the largest departmental academic staff in the College.

Departmental Resources

The College Report for 1973-74 was headed "Living in Deficit" and recorded that, anticipating trouble to come, five committees were set up in 1973 to look into the level of resources which should be allocated to the Departments of Physics and Astronomy, and Chemistry, the School of Environmental Studies, the Slade School, and the Library. The effect on College finances of successive cuts made by the Government in December 1973 and January 1974 was such that by October 1974 it was clear that if the College received no supplementation for inflation it could be running an annual deficit of over £400,000 at the end of the current financial year. This led the College Committee to take immediate measures to restrict expenditure in 1974-75 and outline policies to alleviate the worst effect of the shortfall in funds. These involved economies in administration, reduction of expenditure on academic staff by about 5% during 1975-77, and short-term provision for maintenance of buildings. Each Faculty set about identifying which posts and what expenditure could in the immediate future be curtailed in each Department. After intensive work the Deans were able to report that they could contemplate a target of £365,000 p.a. at October 1974 rates for reductions in staff establishments to be achieved by 1 August 1977. Departments were then asked to define their contributions to the overall target which would involve the least damage to academic commitments; they responded by indicating the suppression or down-grading of posts that were expected to fall vacant through retirement or resignation up to 1977. The Deans were required to monitor the agreed economies, flexibility being preserved by allowing equivalent substitutions; requests to fill vacant posts were to be referred to the Provost, who would consult the Vacancies Committee, the final arbiter, if necessary. In March 1975, while arrangements for the economy programme were being completed, it was announced that a Supplementary Grant of £548,000 had been allocated to the College, this sum being additional to earlier relief grants. The U.G.C. claimed that the total additional grants for 1974-75 approached 50% of the full cost of inflation, assuming that rate were to be about 20%; it warned that the revised grants for 1975-77 would be unlikely to enable making good any accumulated deficit at the end of 1974-75. Although the previously anticipated deficit was made good and £148,000 was allocated to academic departments, it was inevitable that the economies had to stand, no provision being made for additional posts.

Resources Survey of the Department

The ad hoc Committee, under the Chairmanship of Professor G. C. Drew, Dean of the Faculty of Science, was set up by the Professorial Board Executive Committee in November 1973 to review the resources in staff, space, equipment and finance available to the Department of Physics and Astronomy in relation to its academic activities; to report upon the extent of the current research activity supported by external grants, its relationship to the teaching programme, and the interdependence of the research groups concerned, together with an assessment of future continued external support for such activities; and to consider the situation arising from the retirement in 1975 of Sir Harrie Massey, and to make proposals. Members of the Committee were Professors H. Billet (Mechanical Engineering), A. L. Cullen (Electronic & Electrical Engineering), S. P. Datta (Biochemistry), A. G. Davies (Chemistry), C. A. Rogers (Mathematics), and D. M. Wilson ( Scandinavian Studies & Dean of the Faculty of Arts); Professors Boyd and Seaton, Dr. Davis and the author from the department.

Professor Massey presented the Committee with a comprehensive survey of the Department covering its history, geography, research, teaching, resources and problems. In his introductory section the Department was described as "a loosely integrated group of staff and students carrying out a variety of research and teaching activities in many areas of physics and astronomy... The objective ever since 1950 has been to encourage both research and teaching to the maximum extent possible within the limits of national policy on the provision of resources." The research was classified under four main groups, namely, Atomic and Molecular Physics, High Energy Physics, Astronomy and Space Research, and Image Processing, with a varying number of experimental and theoretical sub-groups in the first three, as follows:-

Atomic and Molecular Physics
Experimental:	Leader:
Ionic & Electronic Physics	Prof. J. B. Hasted
Atomic Physics	Dr. A. C. H. Smith
Positron Physics	Prof. H. S. W. Massey
Molecular Physics	Dr. S. J. B. Corrigan
Theoretical:
Atomic Physics & Astrophysics	Prof. M. J. Seaton
General Physics	Prof. H. S. W. Massey
High Energy Physics
Bubble Chamber & Emulsion	Prof. E. H. S. Burhop
Spark Chamber	Prof. F. F. Heymann
Theoretical	Prof. L. Castillejo
Astronomy and Space Research
Engineering & Balloon Platform Projects	Mr. T. E. Venis & Dr. W. A Towlson
University Observatory	Prof. R. Wilson
Infra-red Astronomy	Dr. R. E. Jennings
Ultra-violet Astronomy	Dr. A. Boksenberg
Mullard Space Science Laboratory	Prof. R. L. F. Boyd
Space Science & Atmospheric Structure	Prof. G. V. Groves
Image Processing	Dr. M. J. B. Duff

All groups provided statements summarizing their work in hand. The staff involved in the groups were 57 academic; 36 associate and honorary; 94 technical, 46 being grant paid; and 12 clerical, making a total of 199; in addition there were 65 research students. The Service Groups listed were:- Stores, Workshop, Graphics, Mechanical Design, Photographic and Glass Laboratory; these employed 28 technical staff, 5 being grant paid.

High Energy Physics and Astronomy and Space Research are in the big science area, requiring facilities beyond the capacity of any university or indeed, in many cases, of any country, to provide. It is national policy, described in detail by the Council for Scientific Policy in its "Report of a Study on the Support of Scientific Research in the Universities" (1971) that big science should be supported jointly by the U.G.C. and the Research Councils, the so-called dual support system. The Department's budget in 1973-74 was c. £1.29m of which some £822k came from U.G.C. funds and some £468k from outside grants, mainly from the Science Research Council. As indicated earlier, the high level of support from the College Block Grant is explicable in part by takeovers and transfers during the two quinquennia, 1962-67 and 1967-72. Thus in 1972-73 the Department estimated that £183,330 of the College block grant for that year was derived from the two quinquennial take-overs, resulting in an increase of staff paid from College funds of 18 full-time and half part-time lecturers, 2 research fellows, 7 research assistants of various grades, 29 technicians ranging from higher technical officers to machine operators, and 1 M3 secretary - 57 posts in all. The total departmental expenditure for academic purposes in that year was £1,158,568, the Research Councils and other non-UGC sources providing £477,160 and the College block grant from the University Court and from the earmarked provision for scientific equipment accounting for the remaining £681,408.

On investigation the departmental costs were found to be not badly out of line, in absolute terms, with those of five big science Physics Departments. However the swing from the physical sciences among candidates seeking admission to universities during the past decade had hit the department badly on the physics side; the entry to read physics dropped from 54 in 1968 to 24 in 1973, with a further 4 to read applied physics and 7 to read joint chemistry and physics; fortunately 22 were entered for the astronomy degree. The short-fall of the undergraduate entries for physics courses meant that the department in 1973-74 was significantly more expensive in terms of weighted per capita undergraduate student cost than the majority of other science-based subjects in College, and other comparable Physics Departments. It was however recognised by the Committee that per capita student cost was a quite inadequate criterion on which to base a judgement of the Department. The economies programme adopted by the Faculty of Science was based on a system of allocating to each Department a savings target based on the ratio of that Department's annual expenditure to that of the Faculty as a whole, modified by the ratio of the Departmental student unit cost to the Faculty mean unit cost; it therefore took account both of the absolute cost of a Department and its relative success in attracting students. Since the Department was expensive and relatively unsuccessful in attracting undergraduates, having a staff/student load ratio of 1/4.83, it was given a very high savings target; it accepted having to reduce its annual expenditure from College sources by £92,511 by the end of the 1977-78 session, an enormous saving, amounting to some 25% of the total savings required from all the Faculties in College. The Department's response to this challenge was magnificent, its projected annual savings exceeding the target by almost £6000; none of the savings were detrimental to teaching; on the contrary, re-deployment of staff and some re-allocation of duties provided some increase of resources for teaching.

Members of the Committee visited many of the groups in Gower Street, at the Mill Hill Observatory, at M.S.S.L., at C.E.R.N., Geneva, and at Flaxman Terrace. The Committee was impressed by the very high standard of the research, both theoretical and experimental, throughout the Department. As was to be expected, attention was concentrated on those areas of high expenditure, namely the High Energy Physics, and the Space and Astronomy Groups.

High Energy Physics

The Bubble Chamber Group's two main collaborative projects, neutrino interactions in the Gargamelle Heavy Liquid Chamber at C.E.R.N. and low energy K^- meson interactions in a track-sensitive target in the British National Bubble Chamber at the Rutherford Laboratory, were examined. The Group's contribution to the C.E.R.N. experiment, singled out by the Director-General as being the most important one in the almost twenty years' existence of the Centre, was acknowledged by all as being of crucial importance to the exciting discovery of neutral currents, confirming a unified field theory which linked the weak and electromagnetic interactions as different aspects of the same force law. It was recommended that the Group should be encouraged to restrict itself to one project requiring technical effort in the Department at one time as soon as the Rutherford Laboratory experiment was completed.

The Spark Chamber Group's involvement in four collaborative experiments, three at the Intersecting Storage Rings and one at the Proton-Synchrotron, at C.E.R.N., was also examined. It was appreciated that these experiments demanding continuous interaction by those involved, meant that members of the Group had to be away from College more frequently and for longer periods than those in the Bubble Chamber Group. However the S.R.C. covered almost all of the cost of work apart from academic and technical staff salaries. The Committee concluded that, as long as it was national policy for the United Kingdom to join in collaborative work in high energy physics, it was manifestly to the advantage of the College for staff and postgraduate students of the Department to be involved in the work of C.E.R.N., since it brought great credit to the College at relatively little expense.

Astronomy and Space Research

The Committee noted that the amalgamation of the Departments of Physics and Astronomy had brought together theoretical and experimental groups working in infra-red, optical, ultra-violet and X-ray astronomy, as well as in geophysics and astrophysics. The groups involved in astronomical and space research made use of global facilities such as telescopes at Herstmonceux, South Africa, Teneriffe, Australia and California; balloon launch and recovery facilities in Australia, Texas and Argentina; rocket and satellite launch facilities in the Hebrides, Norway, Sweden, Pakistan, India, Australia, and U.S.A. The fact that the groups were so successful in obtaining use of these eagerly sought-after facilities was a tribute to the excellence of their work. As an illustration, in 1977 the I.U.E. satellite was due to be placed in orbit as an international space observatory for ultra-violet astronomy. Its development was being undertaken jointly by the U.S.A., E.S.A. and the U.K. One of the Department's groups was responsible for the overall scientific definition of the project, the evaluation and calibration of the sophisticated television detector system and the optical design of the telescope sun-baffle system needed to observe faint stars and galaxies in the orbital condition of full sunlight. Similarly the U.C.L. Photon Counting System was proving highly successful on the Mount Palomar 200-inch telescope.

The Mullard Space Science Laboratory was the largest single group in the Department, having a complement of staff and research students of 76 at 1 November 1973. It was the senior and substantially the major U.K. university space research centre. Its main areas of research were X-ray astronomy, solar physics and geophysics involving orbital satellites and sounding rockets. Satellite experiments averaged four to five years preparation before launching and provided data perhaps for another four to five years. About two opportunities to participate in such experiments were being taken up each year. Sounding-rocket experiments averaged about half the corresponding time for preparation and provided data requiring a year or so for analysis. M.S.S.L. was heavily supported by S.R.C.; out of its total budget of c.£384k in 1973-74, rather more than £205k came from S.R.C. It was the only space science group in the country to be financed by S.R.C. in the same way as Jodrell Bank and Sir Martin Ryle's team at Cambridge, i.e., by means of a rolling block grant with annually updated four-year look ahead. Although M.S.S.L. was expensive, it was playing its full part in the Departmental economies programme; over the two-year period 1975-77 it planned to have reduced the annual College expenditure on its staff and other costs by an amount in excess of £43,000. The Committee concluded that the work at M.S.S.L. was of the highest standard; it expressed its conviction that the College would lose greatly in academic distinction if M.S.S.L. ceased to be part of it; and therefore it recommended that the Laboratory should continue to be part of the Department.

In considering the situation at the Mill Hill Observatory, it was appreciated that, although the Observatory was of little use for research, it was of great value for undergraduate teaching, as evidenced by the large amount of observing time logged by undergraduates. A proposal to move the Observatory to a better site, e.g., Holmbury St. Mary, was rejected on the grounds of expense and relative inaccessibility for undergraduate teaching. However the desirability of moving the staff then occupying the Observatory Annexe at 33-35 Daws Lane to Gower Street as soon as possible was stressed. The need soon to replace much of the telescope equipment in the Observatory was underlined, and at the Committee's request the funds for the then-current replacement of the Wilson telescope by one specially designed for teaching were obtained from the Perren Fund, the balance being provided by the Department.

Image Processing

Members of the Committee who visited the Image Processing Group were very impressed by the high standard of the work in progress, namely the development of very sophisticated special purpose computers for the automatic processing of images and recognition of patterns, which had multi-disciplinary implications and very practical significance. The Committee was convinced that the Group should remain in the Department, but that it should be re-housed in Gower Street, preferably near to both the Department and the Department of Statistics and Computer Science when the Flaxman Terrace lease expired.

General Comments on the Research Work

The Committee had recorded its appreciation of the very high academic standard of the research throughout the Department. However it wished to direct attention to some aspects of research in big science areas relevant to its recommendations. Experiments in these areas often had a considerable time-span; for example, ten years or more could elapse between agreement to include a particular experiment in a space vehicle and the completion of the analysis of data. Some experiments under development at M.S.S.L. would be launched in the 1980s; any cancellation or curtailment of such an agreed project would have both national and international repercussions. Once a project, which involved either national or international facilities, had been agreed its timing was out of the control of the U.C.L. group. N.A.S.A. determined the date and timing of the launch of an American space vehicle; if a U.C.L. project was to be included in that vehicle, the equipment had to be tested under simulated and sterile space conditions before being incorporated in the vehicle, and the timing of such tests was again decided by N.A.S.A. Optical and ultra-violet astronomers had to be in South Africa, Teneriffe or California when and for as long as they were allocated access to the respective telescopes; similarly infra-red astronomers, operating from ground sites or balloon platforms in the Argentine, Australia or Texas, had to conform to the conditions imposed upon them. The C.E.R.N. programme determined the work of the high energy physics groups; staff could be required to be absent from College during term time, as well as in vacations, the duration of such absences varying considerably from several days to many months in the case of the spark chamber group. The Committee considered that, as long as it was national policy for such research to be undertaken by universities, it was of the paramount importance that the Department should be encouraged to continue in big science and that it should not be unduly penalised for so doing.

Teaching

On the postgraduate side the Committee noted that there was an increase of postgraduate students from 65 in 1973 to 70 in 1976 when its final report was issued. Although the capacity was 100 there was little chance of this figure being realized owing to the numbers of studentships and suitably qualified candidates then available. Postgraduate training was an integral part of the activities of all research groups, and in many of them students were afforded unique opportunities to participate in research programmes of national importance, using equipment and facilities not available elsewhere. The students in their submissions to the Committee expressed their awareness of this and, with very few exceptions, were highly appreciative of the opportunities available to them. The Committee made no specific recommendations for changes in postgraduate teaching.

The Committee noted the swing away from the physical sciences among candidates seeking admission to Universities during the past decade, affecting physics much more than astronomy. Furthermore in the 1973-74 Session some 28% of the first-year physics students in the Department had failed to qualify for entry to the second-year courses at the end of the Session, compared with 5% of the astronomy students. On the other hand, the more able students derived great benefit from the courses, as evidenced by the number of University prizes and other distinctions gained by them. A questionnaire distributed to the teachers attending the 1973-74 Schools Conference revealed that many of the teachers thought that the Department was only interested in "high-flyers", actively discouraging the less able from applying for entry. At that time the Department had an extremely favourable staff/student load ratio of 1/4.8 based on total staff number or 1/5.4 if effective staff number was used. As with the economies programme, the Committee was impressed by the Department's response to this situation. Active recruitment was showing gratifying results; undergraduate entry had risen from 53 in 1973 to 69 in 1974, with the introduction of a joint astronomy and physics degree course, and 79 in 1975. Extensive changes had been made to the course-unit degree structure, the introduction of half-unit courses allowing a degree of flexibility, reducing the work-load of some students by some 15%, and enabling the less-able student to select less demanding courses, but not retarding the "high-flyers". More staff were involved in the teaching, each half-course unit in the first and second years including separately scheduled discussion periods, to allow teachers to revise difficult topics, to solve specific problems that had arisen, and generally to assess progress. These changes produced an immediate reduction in the drop-out rate of first-year students, namely from the foregoing 28% in 1973-74 to 17% in 1974-75, and of these only, 7% were due to academic failure. The combination of increased entry, reduced drop-out, and the reduction of staff in the economies programme meant that by 1980-81 the staff/student load ratio should be approximately 1/8. The Committee believed this to be a major achievement by the Department.

Effective Staff-Numbers

It being recognised that some members of the Department occupied posts in which they were wholly, or for a significant part of their time, engaged on College rather than Departmental duties; nevertheless they continued to be counted as full-time members of the Department in determining staff/student ratios. Such ratios had become, and were likely to continue to be, important variables in the allocation of resources. The Committee considered it unreasonable to expect departments to be placed in double jeopardy by losing all or a significant part of the services of a member of staff, who accepted an invitation to perform essential College duties, and thereby endangered its claim on any additional resources. The problem affected other departments in College and the Committee believed that such staff should have their College-based time discounted in calculating staff/student ratios. This was already recognized in the cases of the full-time College Safety Officer and the Audio-Visual Aids Co-ordinator. Examples in the Department of Physics and Astronomy were the Tutor to Science Students (whole-time) and the Schools Liaison Officer (part-time). Consideration of unavoidable absences in term-time for internationally based research and the time spent on College duties in the posts cited above, led the Committee to recommend that in the calculation of staff/student ratios an effective staff number of eight less than the absolute number should be assigned to the Department on the understanding that this number should be reviewed periodically.

Quain Professor

The Committee considered that an appointment to the Quain Chair of Physics and Headship of the Department was closely linked with the future development and resources of the Department; consequently it proposed that eight members of the Committee should serve on the Chair Sub-Committee together with two co-opted members. This proposal was endorsed by the Executive Committee. The Sub-Committee was dissolved when its recommendation was accepted that Professor F. F. Heymann should be appointed to succeed Professor Massey in the Quain Chair.

Gas Discharge Studies

On entering the Physics Department Boyd continued the study of gas discharges by means of his screened Langmuir and radio-frequency mass-spectrometric probes, which he had begun in the Mathematics Department. With D. Morris a 12-stage instrument using a series of distributed r. f. fields was developed and applied to study the ions present in helium discharges. The operation of Langmuir probes in electro-negative plasmas was studied with J. B. Thompson, who went on to determine the concentration of negative ions in the positive column of an oxygen discharge. The theory of the collection of positive ions in a low pressure plasma was extended with J. E. Allen and P. Reynolds. With N. D. Twiddy there was developed an electronic method for the Druyvesteyn analysis of the electron energy distribution in plasmas, which was then applied to study the mechanism of striation structure in hydrogen discharges under certain pressure and current ranges; it was to form the basis of many subsequent ionospheric studies.

Optical Techniques

D. W. O. Heddle joined the Department in 1952 as an Experimental Research Assistant to initiate work on the measurement of optical excitation functions and polarization; he had worked with Professor R. W. Ditchburn at Reading on absorption cross-sections in the vacuum ultra-violet. With A. H. Gabriel there was studied the radiation emitted by helium under controlled electron impact to obtain the excitation functions of S, P and D states; the dependence of apparent excitation cross-sections on pressure was also investigated. Heddle and C. B. Lucas carried out a systematic study of the excitation and polarization of electron impact radiation as a function of helium pressure in order to determine the conditions for which secondary processes do not cause significant depolarization of the observed radiation; optical excitation functions and polarization as a function of electron energy were determined for a number of transitions. Then the threshold behaviour of electron excitation and polarization functions in helium was investigated by Heddle with R. G. W. Keesing. Heddle played a leading part in the first observations of ultra-violet radiation from stars in the Southern hemisphere made by two 'telescopes' flown in an unstabilised Skylark rocket launched from Woomera on 1 May 1961 (see p.90). He was primarily involved in the determination of the refractive indices of gases in the vacuum ultra-violet by the Cerenkov method, with Jennings and A. S. L. Parsons (see p.77), and the Rayleigh scattering method, with P. Gill. Heddle's departure to York in 1964 brought the work to an end.

Atomic Physics

The determination of the concentration of atomic hydrogen in mixtures of atomic and molecular hydrogen by continuous flow calorimetry and microcalorimetry formed one of the first projects undertaken in the early fifties, with the view to developing a microcalorimetric probe for measuring the concentration of atomic hydrogen in collision chambers during the determination of various electron impact cross-sections. Dr. A. W. Tickner, a Canadian National Research Council, Overseas Fellow, joined Boyd and Fox for a year on the work, and just before he returned to Canada in 1952, Dr. E. J. Smith, a physical chemist from Newcastle University, joined them as a Warren Research Research Fellow. The microcalorimetry proved extremely troublesome owing to the variability of the recombination of hydrogen atoms on the inside of a small platinum box, situated behind an orifice system through which atoms and molecules of hydrogen effused. This led E. J. Smith, A. C. H. Smith and Fox to make a study of the variability of recombination of hydrogen atoms on metallic surfaces, but eventually the microcalorimetry had to be abandoned.

A. C. H. Smith and Fox determined the viscosity of partially dissociated moist hydrogen, containing up to c. 45% atomic hydrogen, by measuring the rate of decay of the oscillations of a small, bifilarly suspended, hollow glass sphere at pressures in the intermediate region between viscous and free-molecular flow. It was discovered that the viscosity of molecular hydrogen containing 2.5% by volume of water vapour at 20 C was about 7% greater than that of the dry gas, and this was confirmed by computation of the viscosity of mixtures of hydrogen and water vapour over the complete range of water vapour content. This result and the fact that Amour's 1936 values of the viscosity of atomic hydrogen, derived from the 1928 flow experiments of Harteck, based on the dissociation of moist hydrogen, were about 20% greater than the theoretical values calculated by Buckingham, Fox and Gal, led R. Browning and Fox to repeat the flow experiments, but using effectively dry molecular hydrogen. From the viscosities of mixtures of atomic and molecular hydrogen containing up to 70% atomic hydrogen, the mean values obtained for the viscosity of atomic hydrogen at 190, 274 and 373 K were in good agreement with the aforementioned theoretical values. An alternative analysis of the experimental results gave values of the mutual diffusion coefficient for atomic and molecular hydrogen at the foregoing temperatures.

Boyd and G. W. Green developed a modulated crossed beam method for the measurement of the ionization and other cross-sections of unstable atomic gases such as atomic hydrogen. The principle underlying the method was similar to that used by Branscomb and Fite in their measurements of photodetachment of electrons from negative ions. Dr. Wade Fite collaborated in the early part of the work during his sabbatical visit to the department. Ionization cross-sections for molecular hydrogen and for helium up to electron energies of 200 volts justified application of the method to the more difficult case of atomic hydrogen for which preliminary results were obtained. The work was resumed by Boyd and A. Boksenberg, who used an r.f. discharge source and a trochoidal mass spectrometer, having a 100% collection efficiency, for the analysis of the ions. Ionization cross-sections of atomic hydrogen, atomic and molecular oxygen, and molecular nitrogen for electron energies up to 300 volts were obtained and compared with the results of Fite and Brackmann for the first three species.

A notable piece of work on gaseous and surface reactions involving He metastable atoms and resonance photons was carried out by R. F. Stebbings for his Ph.D. degree under the supervision of Hasted; this included the measurement of the absolute yield for He (2³S) metastable atoms incident on a gold surface, and the total cross-sections for collisions between metastable He atoms and He, Ne, Ar and Kr.

Atomic Physics Group

By the early sixties the low energy, experimental work on atomic physics had ceased owing to the dispersal of the personnel. This led Massey to secure an additional established Readership with the special aim of appointing someone of experience and distinction in the field of experimental atomic physics. Stebbings, who had been at the Atomic Physics Laboratory of General Atomic Division, General Dynamics Corporation, San Diego, California since 1958, first as a Staff Physicist and then from 1963 as Scientist-in-Charge, was just the man, and he was appointed to this Readership in October, 1965. He was joined by A. C. H. Smith, who returned to the Department as a Lecturer in 1966, having been working on atomic physics at the General Dynamics Corporation from 1959 to 1962, and thereafter at the A. E. A. Culham Laboratory. Hence the formation of this integral group in atomic physics.

In the initial programme of the Group, mapped out by Stebbings, there were three major experimental projects. The first involved studies of the differential elastic and inelastic scattering of monoenergetic electrons from atoms of the alkali metals, helium and atomic hydrogen using modulated crossed beam techniques. The second was devoted to metastable atom studies, involving the measurement of electron emission coefficients for thermal energy rare gas metastable atoms incident on reproducible controlled surfaces, with the view to making absolute metastable detectors permitting absolute cross-section determinations for a variety of atomic collision cross-section processes.

The third was for atomic hydrogen studies, initially to measure the total and differential cross-sections for excitation from the 1s to the 2s state by electron impact with increasing degrees of refinement, surface detection of the metastables being used throughout. It was planned to install a PDP8 computer in the laboratory to collect, process and display data and to provide some degree of experimental control.

By 1968 the Group included nine additional members, namely three postdoctorals and six research students. Unfortunately Stebbings then returned to America to take up a Professorship at Rice University, Houston, Texas, leaving Smith in charge of the Group. W. R. Newell, a post-doctoral Research Fellow with experience in the determination of excitation and ionization cross-sections at the University of Southampton, joined the Group on his appointment as a probationary Lecturer in January, 1974.

D. E. Burgess, M. A. Hender and T. Shuttleworth obtained their Ph.D. degrees for their contributions in the studies of zero-angle, energy-loss spectra of electrons scattered from sodium and lithium. The first measurements were made of the differential (0-20 deg) cross-sections for the sodium resonance transition (3²S - 3²P) at 54.4, 100, 150 and 250 eV, the results being expressed as absolute differential cross-sections and generalised oscillator strengths by Shuttleworth, Newell and Smith. Further measurements of the differential inelastic scattering of electrons by sodium at zero angle were reported by these authors, absolute generalised oscillator strengths being given for excitation to the 4S, 3D, 4P, 5S and 5P doublet states, and values of reduced matrix elements, optical oscillator strengths and quadrupole transition probabilities deduced for S - S, S - P, and S - D transitions respectively. Shuttleworth, Burgess, Hender and Smith reported the measurement of zero-angle, energy-loss spectra for lithium with incident electron energies from 15 - 190 eV and their analysis to give generalised oscillator strengths for transitions between the 2S doublet ground state and the 2P, 3S, 3P, 3D, 4S, and 4P+4D+4F (unresolved) excited doublet states. The quadrupole transition probability for the 2S - 3D doublet transition, the Racah reduced matrix elements for the 2S - 3S and 2S - 4S doublet transitions were also given.

B. F. Dunning and Smith applied two different methods to determine the secondary electron emission coefficients for rare gas metastable atoms incident with thermal energies on metal surfaces. The crossed beam method with helium, neon and argon metastable atoms incident on atomically clean cadmium surfaces gave values of the coefficient less than 0.5 in all cases, and values in excess of 0.5 for contaminated stainless steel surfaces. The gas cell method was applied for measurements on electrodeposited gold, chemically cleaned stainless steel and copper surfaces, and atomically cleaned cadmium and tungsten surfaces; the results indicated that rather larger coefficients than those previously used should be applied for gold surfaces. The investigations led to the development of an absolute detector for rare gas metastable atoms. Measurements of the ratio of cross-sections for Penning ionization by helium singlet and triplet metastable atoms were made by a beam - gas cell method; the results with Ar, Kr, Xe, O₂, N₂, CO, NO and H₂ showed good agreement with previous gas cell measurements, but disagreement with results obtained in afterglow studies.

Some measurements were made of the total cross-section for excitation of atomic hydrogen to the metastable 2S state and of the distribution of recoil angles of the 2S atoms by means of a modulated crossed beam technique; they indicated that the differences between earlier experimental and calculated values of the cross-sections may have been due to the absence of thermal equilibrium in the beam sources. Research students, M. W. Evans and M. I. Gillespie were involved in this work.

The international reputation of the group was underlined by its attraction of overseas visitors for long and short periods from U.S.A., Canada, France, Germany and Australia.

Ionic and Electronic Physics Group

On entering the Department, Hasted continued with a systematic experimental study of charge exchange for ions with energies between 25 and 900 eV., his first paper reporting agreement with near-adiabatic theory for processes involving only atomic ions and atoms with quite definite energy discrepancies. Then he proceeded to measure charge exchange cross-sections for a large number of singly charged positive, ions in argon, krypton and xenon at energies up to 4000 eV, finding agreement with the 'adiabatic maximum rule'. Electron detachment cross-sections for a number of singly charged negative, ions in collisions with rare gas atoms, measured with the same apparatus, showed unexpectedly high values at low energies with O^-, Cl^- and F^-, possibly due to the presence of excited states of these ions, of low electron affinities, in the beams. However a further investigation of these collisions discounted this explanation.

Hasted then started a collaboration with research students to form a large experimental research team studying the collision of atoms and ions in gases, which was to bring international recognition for him and the work of his group. Measurements were made to establish the region of validity of the adiabatic criterion; to investigate the role of pseudo-crossing of potential energy curves in inelastic heavy particle collisions; to study ion-atom interchange using both drift-tube and afterglow techniques; to investigate 'resonances' or short lifetime, compound negative ion, states in molecules by electron spectroscopy; and to study the further ionization of multiply-charged ions by means of the hollow-beam ion trap. In parallel with these collisional studies, he carried out a programme involving the microwave absorption properties of liquids. His book on the 'Physics of Atomic Collisions' was first published in 1964, a second edition appearing in 1972. On taking up the Headship of the Department of Physics at Birkbeck College on 1st. October 1968, part of his Group went with him, the remainder staying behind under his leadership in the basement of 25 Gordon Street. The latter involved the injected ion drift tube, the curve-crossing spectroscopy, and the hollow electron beam projects.

The first measurements for charge transfer and ionization of gases by heavy ions in the kilovolt region were made by Ph. D. research student, H. B. Gilbody, in collaboration with Hasted. 17 charge transfer cross-sections measured in the 3-40 keV range could in most cases be explained on the 'near-adiabatic' theory, but Ar⁺ in Kr, Ne⁺ in Ar and C⁺ in Kr showed anomalies varying slowly with energies in the 'near-adiabatic' range, possibly due to pseudo-crossing of the potential energy curves; and 23 cases of ionization cross-sections of atoms by positive ions did not appear to conform to the simple adiabatic theory, the value of the cross-section in the adiabatic region appearing to depend upon the reduced mass of the system. Measurements of charge exchange cross-sections for protons, molecular hydrogen and helium ions in hydrogen and the rare gases, and electron detachment cross-sections for negative atomic hydrogen ions in the rare gases were carried out by Hasted in the 100-4000 eV range and by J. B. H. Stedeford in the 3-40 keV range. R. A. Smith collaborated with Hasted in measurements of collisional detachment cross-sections for O^- in O₂, N₂, H₂O; H^- in H₂; O₂^- in O₂; and Cl^- in Cl₂ between 10 and 2500 eV: in all cases, except O₂^- in O₂, charge transfer was found to be negligible. Measurements were also made of partial charge transfer cross-sections for C⁺⁺, N⁺⁺, Ar⁺⁺ in He, Ne, Ar and the results were discussed in terms of divergence from near-adiabatic conditions caused by the crossing of potential energy curves; the single endothermic C⁺⁺ in H₂ behaved adiabatically, but the others, exothermic, showed large cross-sections at low energies; contributions from double charge transfer could not be distinguished in Ar⁺⁺ in Ar.

Hasted and A. Y. J. Chong determined electron capture cross-sections for doubly, triply, and quadruply, positively charged, krypton ions in neon and helium in the energy range, 100-3000 eV. These and the previously measured cross-sections of Hasted and Smith were interpreted in terms of the pseudo-crossing of potential energy curves. On the assumption that for each capture process, the transition only occurred at a certain nuclear separation, an attempt was made to relate the potential energy curve separation at that point with the reciprocal of the separation. Total cross-section measurements of these processes were superseded by differential measurements, e.g., Hasted, S. M. Iqbal and M. M. Yousaf measuring the probabilities of single-electron capture by doubly positive charged, carbon, nitrogen, and oxygen ions, colliding with helium, neon, and argon atoms, as a function of laboratory angle of scattering at energies between 1 and 3 keV. The oscillatory variation of the probabilities with scattering angle was interpreted in terms of the pseudo-crossing of potential energy curves for the initial and final states.

Static-afterglow studies were carried out by G. F. O. Langstroth and Hasted; they used an r.f. mass spectrometer of the Boyd-Morris type, which was inserted as a probe into the afterglow, generated in a glass tube, 90 cm long and 10 cm diameter; they used exciting pulses of 2 ms duration, with a repetition rate of 10 per second, and carried out all observations, including mass-spectrometric adjustments, in less than 2 min. to minimize the 'clean up' of oxygen that occurs through successive pulses of discharge operation. They measured the rate constants for the reactions:

O⁺ + O₂ -> O₂⁺ + O
O⁺ + N₂ -> NO⁺ + N the latter being important in the interpretation of the behaviour of the ionosphere at altitudes up to a few 100 km. M. M. Nakshbandi and Hasted repeated the experiment in a vessel designed to permit variation of the gas temperature, obtaining values of the rate constants at 77, 200, 300 and 375 K. These showed discrepancies with the group's drift tube measurements, which agreed with flowing afterglow measurements at N.B.S. Boulder, Colorado. Since it was becoming increasingly clear that the excited species inevitably present in time-dependent afterglows put this technique at serious disadvantage in comparison with the flowing afterglow technique, it was abandoned in favour of the latter. A 12-inch diameter afterglow tube was developed, excited by pulsed, hollow-graphite cathode, discharge, with approximately laminar gas flow in the range, 10-100 m/s, measured by probe detection of an electric pulse applied across filter-grid wires upstream; electron density and temperature were monitored by floating double probe, and ion density by quadrupole mass spectrometer, both instruments being traversable 30 cm along the axis of the tube. M. R. Mahdavi, M. M. Nakshbandi and Hasted made the first measurements with the tube, namely, to study the dissociative recombination processes following excitation of CO₂ and also CO₂ - He discharges. The temperature of the gas and electrons was of the order of 1000 K, comparison of the rate with that at room temperature suggesting an inverse three-halves power dependence. Further high temperature studies of recombination, including spectroscopic investigations were planned, the programme being supported by the Chemistry Division of U.K.A.E.A., Harwell. In an investigation of two-photon transition in helium, the time-dependent afterglow proved incapable of supporting the requisite He 2¹S populations. Therefore a small flowing afterglow, with microwave cavity excitation was installed; the transition 2¹S -> 6¹S was achieved by the absorption of two photons of red ruby laser light; and pulses of radiation were detected from the upper level.

Advances were made in the application of the drift-tube method, the foremost method for bridging the energy gap between thermal energies and those involved in ion beam-experiments. Measurements were undertaken of rate constants for charge transfer, ion-atom interchange and other collision processes at mean impact energies of c. 0.05-10 eV. C. H. Bloomfield and Hasted were the first to carry out experiments involving the mass analysis of ions entering a drift tube; they relied upon mobility measurements to discriminate between ions arriving at the end of the tube, but it proved difficult to interpret the mobility spectrum unless it had a simple double-peaked form. To overcome this difficulty Y. Kakapo, L. R. Megill and Hasted added a second mass spectrometer, of the Boyd-Morris type, at the exit end. The apparatus was then improved by the addition of an ion source of controllable electron energy to yield only ground-state ions, and the replacement of the Boyd-Morris r.f. mass spectrometer by a quadrupole mass filter of resolution better than 1/120. A 'merged-drift' apparatus was then designed, providing facilities for the simultaneous injection into the drift tube of two separate beams, positively or negatively charged, or neutralized; for the variation of the length of the tube in vacuo; and the control of the temperature of the tube. As illustrative of the measurements made in this field, D. K. Bohme, P. P. Ong and Hasted determined the rate constants for O⁺ in O₂ and N₂ using ground state O⁺ ions; P. P. Ong and Hasted measured the rate constants for charge-transfer processes, Ar⁺ in N₂, O₂, CO and NO; for dissociative charge transfer for He⁺ in N₂; and for the three-body process,

He⁺ + 2He -> He₂⁺ + He.
K. Birkenshaw and Hasted improved both the experimental technique and the calculations of the cross-sections (by Bohme, Ong, Moore and Hasted) based on the nearest resonance method, achieving better agreement between the measured and calculated values for the foregoing reactions involving Ar⁺. M. J. W. Boness and Hasted, designed one of the first four, very low energy (0.1 - 20 eV.), electron spectrometers ever built, and with it observed resonances or short life-time, compound negative ion states in N₂, NO, CO, O₂, and CO₂. The spectrometer used a relatively large 127 deg. electrostatic analyser to produce an incident electron beam, with an energy spread of the order 50 meV, directed into a gas collision chamber so designed that only those electrons scattered through less than 1 deg. emerged from the chamber to be collected, the gas pressure in the chamber being adjusted to produce 20% absorption. They made corrections for the electro-optical focussing effect in their experiments to obtain the true variation of the transmission with electron energy. With I. W. Larkin, compound negative ion states of molecules, N₂, NO, N₂O, NO₂, O₂, CO, and CO₂, detected as structure in the electron total cross-section functions, were interpreted in terms of the Beutler-Fano equation and partially identified by comparison with certain isoelectronic species. L. Moore joined the trio in observing resonances in C₆H₆, C₂H₄, and CH₄; he was involved in the data analysis, devising a convenient numerical method of deconvolution of physical data, based on a Fourier series expansion A second transmission spectrometer, with both monochromator and analyzer, having an energy resolution in the range 15-30 meV, was used in studies of the decay of diatomic molecular resonances into vibrational channels, enabling potential energy curves for the appropriate negative ion states to be calculated; A. M. Awan and I. W. Larkin collaborated with Hasted in these studies. The old transmission spectrometer was phased out in favour of a scattering spectrometer being developed with a view to inferring the azimuthal quantum numbers of the molecular resonances previously studied. The monochromated electron beam was to be crossed with a molecular beam, the post-collision electron momentum analyzer being traversable through polar scattering angles 0 - 120 deg. The development continued with a view to possible commercial exploitation, as envisaged in a S.R.C. Co-operative Award.

In the mid-sixties, Hasted on leave of absence at the Institut Battelle, Geneva, collaborated with F. A. Baker in the use of a Nier source operated as an ion trap to study ionization potentials for step ionization processes of positive ions and the behaviour of the cross-sections for such processes near threshold. This so-called 'sequential spectrometry' was then taken up by several groups. Back at College a more sophisticated experiment was developed in which a toroidal cathode produced an electron beam of annular cross-section, through which a molecular beam was passed, the ions formed being trapped for periods of c. 1s, oscillating radially, and passing through a second, axial, electron beam of variable energy; ions of different charged states were extracted axially through an orifice into a quadrupole mass spectrometer and channeltron detector. In this way, with G. L. Awad, cross-section functions for ionization of multiply charged ions were obtained between threshold and 500 eV., namely for singly, doubly and triply charged argon ions, and doubly and triply charged neon ions.

In the microwave field, Hasted in collaboration with G. W. Roderick made measurements of dielectic constant and loss on a range of aqueous and alcoholic electrolytic solutions at wavelengths from 1.25 - 51.5 cm at temperatures in the range from 3 - 25 C, providing information on the behaviour of the water molecules in the neighbourhood of the ions. Then, with M. A. Shah and P. R. Mason, observations were made of a Stark shift in the microwave relaxation of nitrobenzene. In a microwave absorption study of dielectic mixtures with relaxing components, extensive studies were undertaken of the microwave properties of water absorbed physically in brick and aerated concrete, and chemically in cement, computer calculations of the dielectric theory of mixtures, applied to complex dielectric constants, successfully interpreting the physical absorption data (with L. Moore and M. A. Shah); and a phase change technique was applied to the problem of classifying absorption as physical or chemical (with P. Firth and S. P. Lovell). These studies were followed by 10 cm. wavelength cavity resonator measurements of water complex permittivity at 0.5 C intervals in the range, 15 - 75 C, and then at 0.1 C intervals; the repeatability of the structure in the temperature function, particularly of the dielectric loss, demonstrated that these intervals were sufficiently small to reveal most of the 'thermal anomalies'. Further work was planned with capillaries of different diameters to establish whether the anomalies were surface or volume effects. Filled cavity resonator measurements at 10 cm. wavelength of the dielectric properties of liquid ammonia and sodium-ammonia solutions were carried out with S. H. Tirmazi, the results being consistent with the existence of ionic plasma resonance. The microwave studies of aqueous and ammoniacal solutions were complemented by measurements in the submillimetre band. Hasted and M. S. Zafar collaborated in measurements on water at laboratory temperatures using the new double modulation Fourier spectroscopy technique developed at the National Physical Laboratory under the supervision of Dr. J. Chamberlain; temperature variation, D₂O studies and ionic solution measurements were planned to follow.

High Energy Atomic Collisions Group

After obtaining his Ph.D. degree in 1956, H. B. Gilbody worked as a Research Assistant in Hasted's group until November 1959, playing a leading part in the design of the van de Graaff accelerator. He then joined the General Atomic Division of the General Dynamics Corporation, San Diego, Calfornia as a Research Physicist. This group was formed under his leadership on his return to the Department as a Lecturer in 1961. It studied inelastic ion-atom collision processes at energies ranging up to 500 keV, the van de Graaff accelerator providing mass-analysed beams of the required ionic species. Collisions involving charge rearrangement and excitation were studied, the methods applied including total collection, charge or mass analysis, of the collision products; spectroscopic study of radiation induced in collisions under carefully controlled conditions; and the modulated crossed beam technique.

Collisions involving rare gas ions included the measurement of total cross-sections for slow ion production and electron production and the total apparent charge transfer cross-sections in collisions of rare gas ions with rare gas atoms in the energy range 60 to 450 keV by Gilbody with Hasted, J. B. Ireland, E. W. Thomas and A. S. Whiteman; a study of excitation in rare gas ion-atom collisions in the energy range 100 to 400 keV, including the determination of cross-sections for the emission of some of the more intense lines in the spectral range from 3900 to 6000 Å by Gilbody and Thomas; a study of small angle scattering in charge transfer collisions when beams of protons, singly charged He, Ne, Ar and Kr ions at energies within the 60-250 keV. range were passed through thin targets of H₂, He, Ne, Ar and Kr gases by Gilbody and A. B. Wittkower; and the study of charge neutralization of 60 to 450 keV., singly charged Ne, Ar and Kr ions during passage through both thin and thick targets of the previously mentioned gases by Gilbody and Wittkower. The total cross-sections for slow ion production and for ionization were determined for protons, of energies between 100 and 450 keV, in H, He, Ne, Ar and Kr by Gilbody and A. R. Lee. Proton collisions with atomic hydrogen were studied by Gilbody and G. Ryding, cross-sections for the charge transfer process

H⁺ + H(1s) -> H(n,l) + H⁺ involving capture into all states (n,l) of atomic hydrogen being determined by means of a modulated crossed beam technique in the energy range from 40 to 250 keV. The apparatus was then modified to permit study of the 2s capture process in targets of atomic and molecular hydrogen and helium, the yield of fast metastable atoms being determined by recording the Lyman alpha radiation produced by electric field quenching; Wittkower joined Gilbody and Ryding in this later work. On 1 January 1967 the personnel and associated equipment, including the van de Graaff accelerator, of the Group was transferred to the Department of Physics, Queen's University, Belfast, on Gilbody taking up his appointment to the second Chair of Physics at Belfast.

The Microtron Group

One of the first projects undertaken in the Department was the design and construction of a 4.5 MeV electron accelerator (microtron) for electron scattering studies by Henderson and Jennings under the leadership of Heymann, who had been involved with electron accelerators at Metropolitan Vickers. This, the second such machine constructed, operated at a wavelength of 10 cm, the diameter of the final orbit being c. 30 cm in a magnetic field of 1000 gauss; and a circulating current of c. 2 mA mean was observed at a duty cycle of 0.0004, with a 500 kW peak microwave source. The stability of the machine was studied, the limits of phase and energy within which electrons could be stably accelerated being calculated for a number of voltages by two different methods; generally speaking, the energy and phase of a stable electron could not vary from that of the ideal electron by more than ± 0.1 rest masses and ± 10 deg, the stable regions being independent of the energy of the electrons with the result that the beam from a microtron becomes relatively more monoenergetic as the final energy is increased. The beam had an energy spread of about ±50 keV, and by using a double focusing magnetic spectrometer a 'monoenergetic' beam with a spread of only ±4 keV could be obtained; its sea-angular spread was 1.5 deg horizontally and 0.3 deg vertically. A method of measuring absolutely the energy of the beam itself was developed using a variable pressure gas Cerenkov counter detector; then a Jamin interferometer was incorporated into the pressure system to enable the refractive index of the gas to be determined directly, M. R. Bhiday and P. I. P. Kalmus being involved with Jennings in this work. As mentioned on p. 71, Heddle collaborated with Jennings and A. S. Parsons in applying the Cerenkov radiation method to determine the refractive indices of gases in the vacuum ultra-violet. Heddle working next door to the microtron group, realised that this could be done by comparing the threshold pressures for Cerenkov radiation in the ultra-violet and visible regions for electrons of the same velocity.

Heymann and Jennings carried out experiments on the multiple scattering of 4.5 MeV electrons by Al, Cu, Mo, Ag and Pt foils applying the photographic method to measure the variation of scattered electron intensity with angle; the results were in good agreement with the theory of Moliere into the region of plural scattering, this being the upper limit of angles covered by the observations. Later Bhiday collaborated with Jennings in measurements of the radiative correction for scattering of 4.5 MeV. electrons at different angles from high and low Z foils, with results in reasonable agreement with theory. The facilities of the group enabled K. K. Damodaran and R. M. Curr to establish that the single scattering of 4.33 MeV electrons by heavy nuclei such as Ag, Pt and Ur agreed with Mott's theory, within their experimental accuracy of a few percent, for angles from 45 to 90 deg.

Following the successful operation of this microtron, Heymann and Jennings were joined by D. K. Aitken and P. I. P. Kalmus in the development of a larger machine, based on a 20 ton magnet of pole diameter 7.5 ft. It was brought into operation in the Summer of 1958, the extracted beam being of c. 10^-8 A mean at an energy of 29 MeV; pulsed at a repetition rate of 100 pulses per sec., it had an electron pulse duration c. 2 ms; and by means of a quadrupole lens system, the extracted beam was focused to a spot of c. 2 mm in diameter, corresponding to an angular spread less than 1 deg.

During the development a null method for the measurement of small energy losses in gases at 29 MeV by Aitken, Jennings and R. N. F. Walker, it was noticed that the threshold was not as sharp as had been anticipated from the 4.5 MeV data. This could not be explained until it was realised as being due to transition radiation, which occurs when the environment of a constantly moving electron changes. It was found possible to photograph this radiation, emitted below threshold, using very long exposures. Parsons joined the aforementioned trio in measuring the angular distribution, the variation with pressure, and also the intensity and polarization of this transition radiation.

An experiment to measure Bremsstrahlung spectra emitted at large angles to the incident beam was performed at an energy of 27.6 MeV by Jennings, J. F. Hague and R. E. Rand; the target used was aluminium and the results indicated a cross-section about two standard deviations greater than given by the Bethe-Heitler formula for a point nucleus, the discrepancy being larger when allowance was made for finite size effects. A total absorption spectrometer, which had previously been calibrated by measurement of the 'Bremsstrahlung electron' by Hague and Rand, was used in the experiment. The intensity of the incident beam was measured with a small Faraday cup, the efficiency of which had been determined by a null method applying a toroidal transformer.

Energy loss distributions for 28 MeV electrons after passage through tungsten foils were measured by Jennings and G. R. Davies. Good agreement with theory was obtained for the variation of the most probable energy loss with thickness (maximum c. 2 gm/cm²), but the widths of the distributions were slightly narrower than predicted. The group completed its experimental programme on the machines in 1963.

Double Magnetic Lens Spectrometer

Another of the first projects undertaken in the Department was the design and construction of a beta-ray spectrometer for investigating the nuclear scattering of electrons and positrons, of energies up to 4 MeV, by thin metallic foils. In such an experiment an intense beam of nearly monoenergetic particles is required to be incident on the scatterer in accurately determined directions. G. P. Rundle was awarded the Aithison Travelling Scholarship by the University of Melbourne to join the Department in 1950 as a Ph.D. student and he was assigned to the project; also involved was another Ph.D. student, J. Ellis, together with Griffith and Tomlinson. Both coils of the spectrometer were capable of very fine adjustment in five degrees of freedom; these fine adjustments enabled a detailed study to be made of the effect of coil alignment and separation on the resolution and transmission of the instrument, the incorporation of ring focus notably improving the resolution. The extensive testing of the instrument also included a study of the variation of spherical aberration with coil separation, and the use of a quick and accurate experimental method of plotting trajectories.

The first scattering experiments with the spectrometer were carried out by Henderson and Ellis. Electrons and positrons from a radioactive source were scattered under identical conditions at 0.7 and 1.4 MeV by Al, Ag and Au foils, the incident and scattered particles being counted by means of scintillation counting equipment developed by Heyland and Roberts. The incident beam was a divergent hollow cone of semi-vertical angle of c. 10 deg, the effective angles of scattering being 22.8, 34.5 and 47.5 deg. The results within experimental accuracy of ±5% were in accordance with the predictions of the Dirac theory. Further experiments were performed by Henderson and A. Scott on the multiple scattering of electrons and positrons of energy 0.4 MeV on foils of the same elements using a more strongly collimated, converging hollow beam. The difference between the distribution width for electrons and that for positrons after scattering was found to be smaller than previous measurements had indicated; it was given approximately by the calculations of Mohr. Further work with electrons only using silver and Ilford G5 emulsion as scattering foil materials showed good agreement with the theory of Moliere.

The Emulsion Group

In the Mathematics Department, Burhop had begun to use the nuclear emulsion technique as a means of resuming research in nuclear physics, and was soon on very good terms with C. F. Powell of Bristol who had initially developed the technique. However on moving over to the Physics Department, he became heavily involved in the high pressure cloud chamber, cosmic ray programme, one of the first projects in particle physics to be undertaken by the Department. With the closure of this programme, he turned his attention back to the emulsion technique and in 1956 formed the Emulsion Group, the other members being Drs. W. B. Lasich and F. R. Stannard, research assistants, and D. H. Davis, R. C. Kumar and M. A. Shaukat, research students. The work of the Group was to involve participation in the design, preparation and operation of particle beams for emulsion exposures, followed by the location, measurement, and computer analysis of events occurring inside the emulsion, a team of scanners helping with the more routine of these tasks. As a consequence of the Collaboration (referred to later), frequent meetings were necessary to formulate standard experimental procedures, assemble data and discuss results.

Work began with the examination of a stack of emulsions, which had been exposed to a negative unseparated beam from the Bevatron at Berkeley, in order to study the interaction of K^- mesons with nuclei. However, with this work hardly begun, separated beams of low energy K^- mesons became available and, in February 1957, it was learned at a conference in Bristol that the University of Bristol had just obtained an emulsion stack exposed to such a beam. At a meeting between Powell, G. P. S. Occhialini and Burhop, it was decided to share this new stack of emulsions with other laboratories; thus began the European K^- Collaboration by groups from Bristol, Brussels, Dublin, Milan, Padua and U. C. L., the first large international collaboration of its kind.

The first investigation of the collaboration was a systematic study of the interactions at rest of K^- mesons with nuclei, which established the peripheral nature of the nuclear absorption process and revealed the then surprising result that about 20% of K^- meson capture occurred on more than one nucleon, confirming the importance of nuclear correlations in the nuclear surface, first suggested by D. Wilkinson. The group's involvement with the collaboration was published in three Nuovo Cim. papers (1959-60) dealing with the general characteristics of K^- interactions and analyses of events in which a charged pion is emitted; the emission of hyperons from K^- interactions at rest; and on the observations of fast sigma hyperons emitted from the interaction of K^- mesons with emulsion nuclei. In 1961 the Italian groups left the collaboration, but later it was extended to include groups from Warsaw, Westfield College, Prague, East Berlin and Belgrade, thus becoming the first to include physicists from both sides of the Iron curtain, a step towards an East-West rapprochement so welcomed by Burhop.

After gaining his Ph.D. in 1959, Davis continued to work in the group as a research assistant. He spent 1961-62 as a Fulbright Travel Scholar and Research Associate, working with Prof. Levi Setti at the Fermi Institute in the University of Chicago, and developing his interest in the study of hypernuclei, a field in which he was to become a leading world authority. On returning to UCL he became a lecturer in 1963 and assumed increasing responsibility for the organisation of the work of the group, Burhop maintaining an avuncular interest in the activities of the group and of the collaboration as a whole.

During the period 1962-74 many papers were published on hypernuclei binding energies, spins, decay modes, lifetimes and production mechanisms, and on low energy K^-p scattering and production processes. As highlights, there are selected the study of hyperfragment production by K^- mesons in emulsion stacks irradiated in the separated K^- beam at CERN, Geneva, leading to the discovery in 1963 of the production and subsequent cascade decay of a double hyperfragment, i.e. a nuclear structure containing two bound lambda hyperons, by J. E. Allen, M.J. Beniston, D. A. Garbutt with Davis et al; this led to a determination of the binding energy of the two hyperons in a double hypernucleus. In 1965 a determination was made of the lambda-nuclear potential well-depth from the observed energy releases in the p^--mesonic decays of the heavy spallation products of silver and bromine by P. Allen, Elizabeth Fletcher, D. A. Garbutt, M. A. Shaukat, Davis et al. Burhop's insistence that the anomalies in p⁺ and p^- meson absorption rates following K^- meson capture in nuclei, which had been apparent in the earlier work, could be explained by a 'neutron skin' in heavy nuclei led to a more selective study in 1967 of K^- meson captures in emulsion nuclei by Susan Lovell, Davis et al, which was aimed to ascribe captures involving specific proton and neutron absorption processes to either light (C, N, O) or heavy (Ag, Br) muclei. The result of the study, namely that K^- meson captures on neutrons are about five times more likely in heavy, than in light, nuclei, confirmed Burhop's insistence. Similar, later studies by several workers, including Bethe and Teller, endorsed the result that the extreme periphery of a heavy nucleus was rich in neutrons.

Evidence for the existence of particle-unstable states of the L¹²C and L¹⁴N hypernuclei produced by the absorption at rest of K^- mesons in light emulsion nuclei in 1969 and the subsequent confirmation of the existence of a particle-unstable state of the L¹²C hypernucleus by Davis et al - the so-called discovery of analogue resonance states, which initiated the growth of a thriving hypernuclear spectroscopy 'industry' at CERN, Brookhaven National Laboratory and KEK, Japan. In 1971 an experiment was performed in a six litre stack of Ilford K5 emulsion exposed to stopping K^- mesons at the Brookhaven A.G.S. machine by D. N. Tovee, Davis et al. During the course of an extensive study of the properties of hypernuclei produced by c. three million stopping K^- mesons, a sample of some 7500 meson interactions at rest on hydrogen giving rise to charged S hyperons were recorded, and the interactions were used as a source of monoenergetic hyperons to determine their properties in conditions different from those existing in a hydrogen bubble chamber. The decay branching ratio of the S⁺ hyperon, the ratio of S^- to S⁺ hyperon production, the lifetime of the S^- hyperon, the mean orbital capture time of S^- hyperons in emulsion, and the masses of the charged hyperons were determined.

In 1963 Burhop made what was to become a very important proposal, namely, that the combination of spark chamber and emulsion techniques would permit the location of rare neutrino interactions in a large emulsion stack. Once located the high spatial resolution of the emulsion technique, shorter than 10^-3mm, would allow the direct resolution of the production and decay vertices of any particles, with lifetimes as short as 10^-14s, to be detected. The experiment was carried out at CERN in 1965 by a combined UCL spark chamber and emulsion team, together with the University of Brussels group and the European K^- collaboration representative, demonstrating the viability of the method even though only a few low-energy neutrino interactions were found. The experiment aroused little interest since at that time there was little expectation that such short lifetime particles existed.

The 1966-67 departmental research report records the concentration of the work of the Bubble Chamber and Emulsion Groups into a single group having three sections, (i) Gargamelle, (ii) RHEL-UCL chamber, (iii) Emulsion, under the leadership of Burhop. It states that "The nuclear emulsion section is gradually being run down although it still has an interesting physics programme for the immediate future." Fortunately Davis refused to believe that the technique had become obsolete with the advent of bubble chambers. His persistence received its reward with the resurgence of the hybrid techniques in the seventies.

The discovery of weak neutral currents in 1973, supporting the unification of the electromagnetic and weak interactions and theoretical predictions of new quark flavours, particularly charm, reawakened interest in such hybrid techniques. Consequently Burhop and others suggested an experiment in which neutrino interaction vertices were to be located by estimating the points of convergence in the emulsion stacks of tracks seen in external wide-gap spark chambers. The experiment, E247, was accepted for running in the wide-band neutrino beam at Fermilab in 1975, Burhop, Davis and Tovee taking part. It was successful in locating 37 neutrino interactions in the emulsion, each within a search volume of c. 1 cm³. From one of these a very good candidate for a charged charmed particle was seen to emerge and decay after a path length of 182 x 10^-3mm and a flight time of a few multiples of 10^-13s.

Then in 1979 a second experiment, WA17, similar in concept was performed in the wide-band neutrino beam of the Super Proton Synchrotron at CERN, some 30 litres of emulsion being placed in front of the entrance window of the large hydrogen bubble chamber, BEBC. A total of 169 charged current neutrino interactions were located in this work and from these 5 positively charged, and 3 neutral, charmed particles were seen to emerge and subsequently decay. Their life times were shown to be in the region of 10^-13s as expected from theoretical models. One of the events was uniquely identified as the decay of a L_c⁺ baryon via the mode pK^-p⁺ after a time of flight of (7.3 ± 0.1) x 10^-13s. This was the first observation of this mode of decay of the L_c⁺ baryon and the first unambiguous determination of the true time of flight of any observed particle. Mention is also made of the Group's participation in the WA75 experiment, using a combination of electronic and emulsion techniques at CERN in 1985, which revealed the first example of the hadronic production of a pair of beauty particles, together with their decays into charmed particles, both of which also decayed in the emulsion.

Cloud Chambers

During the 1951-52 Session Tomlinson, at Massey's suggestion, began work on the construction of two high pressure cloud chambers, based on a design of the late Professor E. J. Williams and subsequently operated by Dr. G. R. Evans at Aberystwyth, where Massey had been an external examiner in physics. It was planned to use one alongside the synchrocyclotron at AERE Harwell to study the scattering of protons and deuterons in light gases, and the other for cosmic ray research at high altitudes when Helmholtz coils, producing a magnetic field of about 7,000 G, had been constructed. In November 1952 he and Massey visited cosmic ray research stations in Switzerland and Italy to select a site for such research. This led to acceptance of the hospitality offered by the Physics Department of the University of Padua at its laboratory on La Marmolada in the Dolomites at an altitude of 2,020 m. A joint programme of research on elementary particles in cosmic radiation was initiated in 1953 with Dr. Evans, then at the University of Edinburgh, and his chamber was installed on La Marmolada in the summer of 1953. Operations continued for nearly three years until it became apparent that accelerators were becoming capable of achieving energies adequate for the production of at least some strange particles. Some 8000 photographs were taken of local penetrating showers produced by the cosmic radiation. This was the most systematic work then carried out using such a chamber and it enabled a thorough evaluation to be made of its usefulness as a research tool; provided valuable experience in the study of analysis techniques; and information about the production of V particles, interactions in the chamber gas, and electron pairs accompanying local penetrating showers. It led to some dozen papers, six of which appeared in the Report of the Conference on Recent Developments in Cloud Chamber and Associated Techniques held under the joint auspices of the Physical Society and UCL in March 1955. Departmental members involved in the project included J. P. Astbury, P. Baxter, F. W. Bullock, E. H. S. Burhop, H. S. W. Massey, A. J. Metheringham, N. Morris, F. R. Stannard and H. S. Tomlinson.

The long recycling time of the high pressure cloud chamber imposed serious limitations to its applications with cosmic rays or particle accelerators. In its original form this time was 15-20 minutes between expansions, M. J. B. Duff and N. Morris showing that the magnitude of the temperature gradient established in the gas during the cycle was the determining factor. As a result of the difficulties found by A. P. Banford, W. E. Duncanson, T. C. Griffith and W. S. C. Williams in finding suitable operating conditions for the investigation of the scattering of 144 MeV protons by deuterons at Harwell, Tomlinson introduced a more elaborate cycle requiring the use of sophisticated high pressure techniques involving either fast recompression or overcompression, thereby reducing the recycling time to 1 minute. However this improvement alone was not sufficient to permit efficient use of the Harwell proton beam. D. J. Cairns, T. C. Griffith, G. J. Lush, A. J. Metheringham and R. H. Thomas established that satisfactory efficiency could be attained by using a selection system of scintillation counters to trigger the expansion only when specific interactions occurred in the gas, thereby allowing up to 30 useful events per hour to be photographed.

Nuclear Physics Group

This group under the leadership of Griffith exploited the counter-controlled, high pressure, cloud chamber for investigations of nuclear reactions involving the measurement of low energy particles. The photographs, usually gathered at c. 40 per hour, were analysed using a semi-automatic measuring table, the data being punched on tape and then processed by the University of London Atlas computer.

In an investigation of p-He⁴ scattering, the afore-mentioned quintet determined the differential cross-section for elastic scattering and for the pick-up process, He⁴(p,d)He³ at 53 ± 4 MeV, the 147 MeV, 46% polarised, proton beam from the Harwell synchrocyclotron being degraded by an aluminium absorber to give that mean energy at the centre of the cloud chamber. The total cross-section for inelastic p-He⁴ reactions, with no fast particles at laboratory angles less than 10 deg, was found to be 107.7 ± 4.4 mb at that energy. The ratio of inelastic to total cross-sections was found to be 0.40. J. E. Nicholls and A. Craig joined Messrs. Griffith, Imrie, Lush and Metheringham in an extension of p-He⁴ scattering to 141 ± 2 MeV at Harwell. Some 3000 interactions were analysed, the results including the differential cross-section for elastic scattering and the total cross-sections for all the interactions energetically possible at 141 MeV. The former were in good agreement with other results at that energy, the latter being the then only available data. The total cross-section of each reaction channel was observed, that for the afore-mentioned pick-up process being very small; the ratio of inelastic to total cross-section at 141 MeV was found to be 0.49. The differential cross-section for the neutral spectrum for the He⁴(p,pn)He³ reaction was also determined. Messrs. Esten, Griffith, Lush and Metheringham investigated the inelastic scattering of 135 MeV protons by deuterium. The differential cross-section and energy spectra for both the fast neutron and for the low energy spectator protons emitted in the d(p,n)2p reaction were measured. The results were compared with impulse approximation calculations and, in the case of the energy spectrum of the spectator protons, the ratio of the theoretical to experimental cross-section was extrapolated to the pole at -1.113 MeV.

The group also undertook a series of scintillation counter experiments using 50 MeV protons from the Proton Linear Accelerator at the Rutherford Laboratory. For the investigation of polarisation parameters in p-p scattering at low energies, G. J. Lush, D. C. Imrie and T. C. Griffith developed a proton polarisation analyser for a measurement of the triple scattering parameter 'D' in p-p scattering at 50 MeV. A. J. Metheringham then joined them in the use of the analyser to measure the depolarisation parameter for 50 MeV p-p scattering at 70 deg (c. m.). This enabled the magnitude of the 3P_o phase shift to be determined with higher accuracy than theretofore and hence improved the phase-shift analysis of the 50 MeV data. This work was followed by a measurement of the spin rotation parameter, beta, for p-He⁴ elastic scattering at 48 MeV. The parameter was measured at 9 laboratory scattering angles between 11 and 90 deg, the results helping to minimise the number of acceptable phase-shift solutions in such elastic scattering; L. A. Robbins replaced Metheringham in the quartet of experimenters involved in this work. With C. J. Batty of the Rutherford Laboratory, the differential cross-section for p-p elastic scattering at 49.41 MeV was measured at 30 angles between 13 and 90 deg (c. m.) with an absolute precision of 0.5 to 0.7 % over most of the angular range, the results being included in a phase-shift analysis of all the then available 50 MeV p-p scattering data.

The Bubble Chamber Group

The bubble chamber was invented by D. A. Glaser at the University of Michigan, U.S.A. in 1952, for which he was awarded a Nobel Prize in 1960. Shortly afterwards, Dodd, who had been in charge of the work on the electron synchrotron, entered the field, building one of the first small chambers in Europe. In June 1955 he was awarded an Astor Foundation Fellowship as a Visiting Professor to spend five months in the U.S.A. at the Brookhaven National Laboratory and Glaser's Laboratory. On his return the Group was formed, first exploring 'clean' chambers, but soon concentrating on heavy liquids. In 1959 the Department was commissioned with the design and construction of a large, heavy liquid, bubble chamber in conjunction with the Rutherford High Energy Laboratory, Tomlinson being the project leader. The chamber costing nearly £400k was built at the Rutherford laboratory. Its internal dimensions were 145 x 55 x 46 cm and it was capable of operation at pressures in the range, 15 - 35 atmos. and temperatures between 30 - 80 C in a magnetic field of c. 21.5 T. The chamber could be used with a wide variety of liquids ranging from the hydrogen rich propane, C₃H₈, to such liquids as trifluorobromomethane, CF₃Br, whose chief virtue is the high conversion rate of gamma rays to electron-positron pairs. It was operated for the first time on 29 October 1965. The UCL group involved in the project numbered at times fourteen, the bulk of the design work being carried out by a team of six, namely Tomlinson, W.A. Towlson, T. E. Venis and three draughtsmen. During the six years of the project this team produced over 650 drawings and the manufacturing specifications besides vetting numerous tenders and contract drawings, close liaison being maintained with the National Institute for Research in Nuclear Science, which handled the services and placed the contracts. Among the physicists involved in the project were Henderson, Stannard, Bullock and Esten.

Before the first experiments were carried out with the chamber, the group were involved in the analysis of film obtained from Berkeley and CERN. In the Berkeley experiment (23), 230,000 pictures were taken involving stopped K^- mesons from the Bevatron in a 30" chamber containing a mixture of equal parts of C₃H₈ and CF₃Br, the Group receiving a third of the film. In the CERN experiment (T8), 250,000 pictures were taken involving 1.5 GeV/c K^- mesons from the proton synchrotron entering the 1m Ecole Polytechnic chamber containing C₂F₅Cl; the Group took one quarter of the film, the remainder being shared equally between the Ecole, CERN, Bergen, and the Rutherford Laboratory. The CERN experiment (T11) yielded 150,000 pictures, 3.4 GeV/c K^- mesons from the proton synchrotron entering the 1m CERN chamber containing CF₃Br; the collaboration was similar to that in T8.

Beta-decay of L^o-hyperon: the short radiation lengths characteristic of heavy liquids, typically between 11 and 25 cm in the foregoing experiments, are particularly suited to the detection of electrons; hence much of the Group's work concentrated on the leptonic decays of hyperons. The first investigation was into the decay:

L^o -> p + e^- + n

The decays were recognised by the characteristic spiralling of the secondary electron. One of the more difficult aspects of the work was the correct evaluation of the probability of the electron stopping in the chamber. Bremsstrahlung and ionization energy loss, scattering, and magnetic curvature had to be taken into account. The problem was solved by D. J. Miller's Monte Carlo programme, which formed the basis of the analysis used in the 23 and T8 experimental results. The two experiments yielded values of (0.82 ± 0.13) x 10^-3 and (0.78 ± 0.12) x 10^-3 for the branching ratio into the modes:

L^o -> (p + e^- + n) / L -> (n + p), the most accurate determination then available. The investigations of the form of the interaction in the beta-decay of the lambda hyperon were the first of their kind. Henderson and Stannard were the other members of the Group involved in these investigations.

Muonic-decay of the L^o-hyperon: the other leptonic decay mode of the lambda hyperon, namely:

L^o -> (p + m^- + n) was looked for in experiments 23 and T8, the event being recognised by observation of the muon coming to rest and decaying into an electron. The background arising from the chain of events: L^o -> p + p^- : p^- -> m^- + n presented difficulties. With the negative pion decaying in flight, it was often impossible to distinguish the negative pion-negative muon decay from a scattering of a negative muon. The background events were about fifty times more numerous than the genuine muonic decays. However the UCL group involving Knight and Stannard were able to show that some genuine lambda-mu decays would have configurations that could not be simulated by the background chain of events, and based on four events of this type, the combined result of the two collaborations was: L^o -> (p + m^- + n) / L^o -> (h + p) = (0.13 ± 0.07) x 10^-3.

This value was consistent with that from phase space considerations, namely that it should be a factor of 6.2 less abundant than the lambda-beta mode.

Beta-decay of the charged S-hyperons: the T8 collaboration was one of the first groups to publish a value for the decay rate:

S^- -> n + e^- + n The analysis made extensive use of the UCL Monte Carlo method developed in connection with the Lb experiment. A value of (1.15 ± 0.4) x 10^-3 was found for the branching ratio: S^- -> (n + e^- + n) / S^- -> (n + p^-) by Miller, Stannard et al. No examples of the leptonic decay of the S⁺ hyperon were found in a sample of 11,000 normal-mode decays of S⁺ particles. A search was made in the T8 film for the decay:

w^o -> e⁺ + e^- Only one probable event was found by B. S. Luetchford, Stannard et al; this allowed an upper limit of 2.8 x 10^-3 to be placed on the ratio of the decays: w^o -> (e⁺ + e^-) / w^o -> (p⁺ + p^- + p^o). Investigations into X-hyperon properties: although the heavy liquid bubble chamber has no particular advantages over the hydrogen chamber in the study of the decays of X^--particles:

X^- -> L^o + p^- the detection of g-rays from p^o by conversion into electron pairs is an ideal technique for studying X^o-decays: X^o -> L^o + p^o

Film from the T8 and T11 experiments was used for investigations into the properties of X hyperons. These included determinations of the masses of X^- and X^o, giving a mass difference of (6.8 ± 1.6) MeV/c² in excellent agreement with the value of (6.7 ± 0.4) MeV/c² deduced from the SU₃ model; the lifetimes of these hyperons, including the first determination of that of X^o ; and the asymmetry parameters in the X^- decay. Low energy p - p interaction: study from Ke₄ decays:
In the autumn of 1965 the Group initiated and organized an experiment at CERN involving collaborating groups from Berkeley and Wisconsin to study the rare K⁺ decay mode:

K⁺ -> p⁺ + p^- + n + e⁺ 530,000 pictures were taken at the CERN proton synchrotron in the CERN heavy liquid bubble chamber, the exposure yielding 13 x 10⁶ stopping K⁺. The chamber was filled with C₂F₅Cl which has a radiation length of 25 cm. The film was equally divided between the three collaborating teams and yielded 269 events of interest, a significant increase on the previous world total of 69. The branching ratio for the rare decay mode was found to be (3.25 ± 0.35) x 10^-5 and the values of four form factors were determined, the importance of two of them being established for the first time. Perhaps the most important result to emerge from this work was an estimate of the low energy p - p S-wave phase shift. No evidence was found for the existence of a s-meson. The study provided further weight to the principle of time reversal invariance and the locality of lepton production.

No example was found of the mode:

K⁺ -> p⁺ + p⁺ + n + e^- giving an upper limit of 7 x 10^-7 at the 95% confidence limit. The absence of such a decay provided evidence in favour of the DQ = DS rule for axial-vector currents in weak interactions. Messrs. Billing, Bullock, Esten, Govan, Henderson, Knight, Miller, Tovee and Treutler took part in the work.

Search for evidence of C-violation:

On returning to England the Group became involved with what started as an engineering run of the newly commissioned UCL-RHEL heavy liquid chamber at the Rutherford laboratory. A 930 MeV/c p⁺ beam from Nimrod was directed in the chamber containing CF₃Br, its short radiation length of 11 cm making possible the search for the suggested C-violating decay mode:

h -> p^o + e⁺ + e^-

where the decay gammas from the p^o are detected by their conversion to e⁺e^- pairs in the liquid. In the experiment, which was carried out in collaboration with Oxford, 600,000 pictures being taken. It resulted in no example of the decay mode being found, leading to an upper limit to the branching ratio of 3.7 x 10^-4 at the 90% confidence level, a value smaller than any previous result by a factor better than two. The aforementioned team members, except Treutler, were joined by Owen, Stannard and Miss E. Tompa in the search. The decay modes of the eta meson were also studied in the experiment, a measurement of the ratio: h -> 3p^o / h -> p⁺ + p^- + p^o being made. 170,000 pictures from the run yielded 260 events with five gammas and 70 events in which all six from the 3p^o mode converted, the events being selected by means of a template which excluded subjective assessment of background arising from bremsstrahlung gamma-rays. The final evaluation of the ratio was R = 1.47 (+0.20, -0.17), an estimate in satisfactory agreement with theory. The Group members involved in this measurement were Bullock, Esten, Miss Tompa, Govan, Henderson, Owen and Stannard. The experiment also led to the observation for the first time of electron pairs of high invariant mass in 830 MeV/c p⁺-nucleus interactions by Esten, Govan, Knight, Miller and Tovee. This was one of the first manifestations of vector meson dominance of the coupling of the photon to strongly interacting particles. The second major experimental investigation with the UCL-RHEL chamber was a study of the lifetime and decay parameters of the X hyperons, which started in the autumn of 1968. The chamber, filled with a propane-freon mixture of radiation length 30 cm, was exposed to a 2.1 GeV/c separated K^- meson beam from Nimrod. 640,000 pictures were taken with a mean of 2.8 interacting K^- per picture. Workers from CERN, Brussels University and Tufts University, USA joined the Group in the investigation. The X^o and X^- lifetimes and parameters were measured to be (3.04: +0.26,-0.23) x 10^-10 and (1.73: +0.08,-0.07) x 10^-10 sec respectively; and (- 0.84 ± 0.27) and (-0.42 ± 0.11) respectively. These values agreed with measurements using different techniques and were consistent with predictions of the I = ¹/₂ rule. The experiment also permitted a direct determination of the X^o and X^- masses, namely (1315.2 ± 0.9) MeV/c² and (1312.12 ± 0.41) MeV/c² respectively. Messrs. Azemoon, Bartley, Miller and Stannard joined in the investigation.

During the 1966-67 Session the Group became actively concerned with the CERN project, initiated by the French under Prof. A. Lagarrigue, for building a very large, heavy liquid chamber, called Gargamelle. The following Session saw the combination of the Bubble Chamber and Emulsion Groups under the general leadership of Burhop, the work of the former being split into two sections, Gargamelle, headed by Esten, and UCL-RHEL, headed by Stannard, Davis remaining in charge of the Emulsion Section. The sections were not exclusive, members of the combined group assisting in machine exposures for a particular section and some work involving different sections. In the 1968-69 Session a grant of £201,000 was received from the SRC for setting up a Gargamelle film analysis unit. This enabled the recruitment of technical staff and the purchase of a Honeywell DDP516 computer for the on-line analysis of Gargamelle film when the chamber became operational. Thus the team became the only British one involved in the European Gargamelle collaboration, consisting of laboratories from Aachen, Brussels, CERN, Ecole Polytechnique, Milan, Orsay and UCL. The UCL team consisting of Bullock, Esten, Jones, McKenzie, A. G. Michette, R. H. Schafer and R. G. Worthington, were involved in obtaining a 'double first' from Gargamelle in 1972, namely the first observation of hyperon production by antineutrinos in the first experimental results from the chamber. The production of L^o and X^o- hyperons by the CERN antineutrino beam traversing the chamber was used to estimate the production cross-section on protons, the result being compared with predictions of the Cabibbo theory for the process. However this was completely overshadowed by the discovery of the existence of neutral currents in the summer of 1973, an event acclaimed by the Director-General of CERN as the most important and significant discovery made in fifteen years of experimentation at CERN. A search was carried out for neutrino-like interactions without muons or electrons among their secondaries, the motivation being the lack of experimental data on semi-leptonic interactions induced by neutral currents. Interest in the subject had been revived by the development of renormalizable theories which unified the weak and electromagnetic interactions and required the existence of neutral currents.

In the experiment, the Gargamelle chamber, of length 4.8 m, diameter 1.8 m, was filled with heavy freon, CF₃Br of density 1.5 x 10³ kg m^-3, providing a total detector mass of about 10 tons, situated in a magnetic field of 2 T; and it was exposed to the CERN neutrino and antineutrino beams. In the analysis based on 83,000 neutrino and 207,000 antineutrino pictures, the former pictures yielded 102 events not containing a muon or electron, and 428 containing only one muon, among the interaction products, whereas in the latter pictures the corresponding numbers were 64 and 148. The UCL team involved consisted of the aforementioned members, with the exceptions of Messrs. Schafer and Worthington being replaced by Messrs. G. Myatt and W. G. Scott. The personal contribution of Bullock, the leader of the UCL team, was so outstanding that he was selected by the European collaboration to make the first presentation of the discovery at the International Symposium on Electron and Photon Interactions at High Energies held in Bonn, August 1973.

Other experiments of the collaboration in the Massey period included (1) a search for elastic muon neutrino electron scattering which revealed for the first time one event in which a muon antineutrino scattered off an electron; (2) a measurement of high energy, total cross-sections for electron neutrino and antineutrino scattering by nucleons, including a test of the muon number conservation law, and the placing of a limit of 2.4 GeV/c² for the mass of the 'Georgi-Glashow' type heavy lepton; (3) a measurement of total cross-sections for muon neutrino and antineutrino scattering by nucleons as a function of energy, the results being compared with predictions of scaling and charge symmetric hypotheses; and (4) a determination of the differential cross sections in freon of inclusive charge-changing neutrino and antineutrino interactions on nucleons in the energy range 1-11 GeV with respect to Bjorken scaling variables, the observed quark and antiquark momentum distributions being compatible with the predictions of quark-parton models fitted to electron scattering data. The common members of the UCL team, namely Bullock, Esten, Jones, McKenzie and Michette, were joined by Myatt, J. Pinfold and Scott in (1); by Myatt and Pinfold in (2); by M. Derrick, Myatt and Scott in (3); and by Myatt and Scott in (4).

In the spring of 1969 the UCL-RHEL section of the Group was associated with physicists from CERN and RHEAS in testing a new technique, involving a track-sensitive target (TST) of liquid hydrogen in a hydrogen-neon chamber, in the 1.5 m cryogenic bubble chamber at RHEL. It was demonstrated that adequate measurement accuracy on tracks within the hydrogen target could be obtained whilst recognising the characteristic spiral of electron tracks in the heavy hydrogen-neon mixture outside. In 1973 the UCL group collaborated with groups from the universities of Durham and Warsaw in a TST experiment which was to become the most complete study to date of the low energy K^-p interaction. The liquid outside the target was a molar mixture of 0.78 neon and 0.22 hydrogen, chosen to give enhanced conversion of gamma rays to electron pairs with a radiation length of c. 45 cm compared with c. 10 m in hydrogen. A negative kaon beam, produced at 0 C from a copper target in a proton beam extracted from the RHEL, NIMROD accelerator, was transported at 620 MeV/c to the chamber, where it was degraded to c. 250 MeV/c by a block of aluminium inside the chamber in order to stop most of the kaons inside the hydrogen. 225,000 pictures were taken and analysed, the results being presented in a series of five papers. These were entitled 'Charged sigma hyperon production by negative kaon meson interactions at rest' (R. J. Nowak, J. Armstrong, D. H. Davis, D. J. Miller and D. N. Tovee et al); 'The Kbar-N channels at low energies' (D. J. Miller); 'Kaon scattering and charged sigma hyperon production in K^-p interactions below 300 MeV/c' (J. H. Bartley, D. H. Davis, D. J. Miller, D. N. Tovee and T. Tymieniecka et al); 'Charge-exchange scattering in K^-p interactions below 300 MeV/c' (J. E. Conboy, D. J. Miller and T. Tymieniecka et al); and 'Neutral hyperon production in K^-p interactions at low momentum' (J. E. Conboy, D. J. Miller and T. Tymieniecka et al). The results of this TST comprehensive study of the low energy K^-p interactions corrected previous measurements of the ratios of the charged sigma hyperons produced at rest, and measured the difference between the I-spin 1 and I-spin 0 scattering lengths with great precision. They also demonstrated the persistence of p-waves in the lambda-final state down to the lowest accessible energy.

Spark Chamber/High Energy Physics Counter Group

Before establishing this group Heymann and his collaborators, namely D. G. Davis, R. C. Hanna and C. Whitehead, took part in an international successful experiment with the CERN synchrocyclotron to test the conservation of parity in strong interaction processes. Later, in a co-operative project with AERE, Harwell, he led the UCL team, including Messrs. Davis and Ghani, who were joined by R. C. Hanna, A. L Read and G. Heymann, in a study of the polarization of protons recoiling from collisions with neutral pions at 265 MeV. This was a difficult experiment because of the poor quality of the available meson beams, but Heymann devised a new polarimeter, the 'Venetian blind counter', to overcome these difficulties.

It was early in 1961 that Heymann began work on the development of spark chambers when they were still in the initial development stage. Rapid progress was made and in 1963, in collaboration with the Westfield College Spark Chamber Group, spark chambers and scintillation counters were used to study the production of neutral pions in collisions between ingoing 600 MeV protons and stationary protons in a liquid hydrogen target at CERN, enabling a comparison to be made between experiment and Selleri & Ferrari theory. The collaboration then undertook a study of the elastic scattering of positive and negative pions by protons at a range of energies near 2 GeV to investigate the spins and parities of two pion-nucleon excited states, N*_1/2(2190) and N*_3/2(2420), then recently discovered in that energy range. The experiments were carried out at RHEL using pion beams produced by bombarding an internal target with protons in NIMROD, the 7 GeV proton synchrotron. Ten differential cross-sections were measured in the range 1.72-2.80 GeV/c pion laboratory momentum for both positive and negative pion-proton collisions. The results were analysed on the bases of optical models and Legendre polynomial expansions, and the interpretation of the structure of differential cross-sections in terms of interference between resonant and background amplitudes was critically examined. The data provided by this group of experiments continued to be used in new and improved phase-shift analyses of the pion-nucleon system. Members of the group involved in this work were W. Busza, B. G. Duff, D.A. Garbutt, F. F. Heymann, C. C. Nimmon, K. M. Potter and T. W. Swetman.

Then in 1965 a combined UCL spark chamber and nuclear emulsion group, together with the University of Brussels group and the European K^- collaboration representative, demonstrated at CERN the viability of the combined techniques to locate rare neutrino interactions in a large emulsion stack.

Following the development of a PDP-8 computer-controlled, system of scintillation counters and core-readout wire spark chambers, the group collaborated with RHEL in a series of experiments on kaon-proton elastic scattering to advance the understanding of the kaon-nucleon interactions. Firstly the differential cross-section for K⁺p elastic scattering was measured at 26 incident laboratory momenta between 1.4 and 2.3 GeV/c in an experiment using an unseparated beam from NIMROD at RHEL. Diffractive behaviour was found at the lowest measured momentum, becoming more prominent with increasing momentum. An expansion of the angular distributions in terms of Legendre polynomials showed no marked structure of the expansion coefficients as functions of the incident momentum. The measurements could be adequately described by a number of existing phase-shift solutions within 5% of their published values; also Regge-pole extrapolations represented the data satisfactorily. This was followed by measurements of the differential cross-sections of K^-p elastic scattering at 13 incident laboratory momenta between 1.094 and 1.377 MeV/c, a region where there had been few previous measurements, and thereafter at 19 momenta between 1.732 and 2.466 GeV/c. The former data showed the characteristic forward diffraction-like peak and backward dip, and were adequately described in shape by certain published partial-wave analyses of the KN system. Strong diffractive peaks, followed by dips, were exhibited by the latter data. The differential cross-sections were fitted to a linear superposition of Legendre polynomials, there being some structure in the coefficients at c. m. energies near 2180, 2270, 3214 and 2370 MeV, but it was not possible to extract possible resonance parameters without a full partial-wave analysis.

The UCL-RHEL collaboration also used the computer-controlled system of scintillation counters and spark chambers to measure the differential cross-sections for elastic scattering of negative pions by protons at 16 momenta between 996 and 1342 MeV/c corresponding to a centre of mass energy range of 1670 to 1850 MeV, where there was some confusion about the existence and properties of nucleon resonances with masses near 1700 MeV. Some of the data and previously published cross-sections were in excellent agreement. The cross-sections were compared with the predictions from two recent phase-shift analyses of the energy-independent type, from which it was possible to obtain good fits over the entire momentum range. Messrs. P.A. Barber, T. A. Broome, B. G. Duff, F.F. Heymann, D. C. Imrie, G. J. Lush, E. N. Mgbenu. K. M. Potter, L. A. Robbins, R. A. Rosner, S. J. Sharrock and A. D. Smith comprised the UCL team involved in these collaborative investigations. When the International Storage Rings (ISR) became operational at CERN in 1971, the Group became involved in an international collaboration between British and Scandinavian universities, RHEL and CERN to carry out ISR experiments. B. G. Duff, who was attached to CERN as a Visiting Scientist from 1971-72, played a leading role in these experiments. In the first experiment a large solid angle, muon detector was used to measure the high energy, transverse momentum, muon spectra to provide evidence for the existence of the intermediate vector boson, a carrier of the weak electroforce. A study of selected events from c. 500,000 pictures showed agreement with muon spectra predicted by Monte Carlo calculations, but no evidence for the production of the boson. However the upper confidence limit for the production cross-section of single muons with momentum greater than 6 GeV/c implied a new, very much higher, minimum mass limit for the existence of the boson. Another experiment involved measurements on massive particle production at 62.5 deg to the bisector plane of the ISR for 53 GeV c. m. energy, including a search for quarks. Although no quarks were seen among the 7 x 10⁷ charged particles entering the detector, a remarkably large number of antideuterons were observed, the relative rate of production of antideuterons to negative pions being (5 ± 1) x 10^-5 at transverse momentum 0.7 GeV/c, the deuteron to antideuteron rate being 3.7 ± 1.2. In a series of experiments, single-particle inclusive spectra were obtained for charged pions, kaons and protons in proton-proton collisions at c. m. energies from 23 to 63 GeV at angles from 30 to 90 deg and for the transverse momentum range 0.1 to 4.8 GeV/c. Over ten million events were recorded on magnetic tape and analysed using the RHEL 370/195 computer. The observed charged-particle, production spectra indicated the existence of two domains, a low and a high transverse momentum domain, with a transition region at 1.0 to 1.5 GeV/c. The domains were different with respect to the form of the transverse momentum distributions, the dependence of the production cross-sections on the collision energy, and the composition of the charged-particle flux. The low transverse momentum data in the central region did not show a constant energy-independent particle production as suggested by the Feynman scaling laws. The profusion of particles produced with high transverse momentum provided strong indications of an inner structure of the proton. Finally, the particle ratios provided an important test for the various models of the strong interaction at high energies. Messrs. B. G. Duff, F. F. Heymann, M. N. Prentice, K. M. Potter, D. R. Quarrie and S. J. Sharrock were involved in these ISR experiments.

In the last collaboration undertaken in the Massey period, elastic scattering and coherent single, and double, pion production in proton-helium interactions at 18.6 GeV/c were investigated with groups from Uppsala and CERN. The elastic t-distribution was found to have a somewhat steeper slope than predicted by the Glauber approximation, and the inelastic angular distributions involving single-pion production were consistent with several spin-parity states contributing at all nucleon-pion masses. The main aim of the double-pion production experiment was to look for features in the distributions of mass and angles of the p^+- system, which could originate from the fact that the system was produced only by isospin-zero exchange. Two enhancements in the p^+- mass spectrum were found at 1.49 and 1.71 GeV/c², both well fitted by Breit-Wigner resonances. The decay angular analysis indicated the presence of several interfering states in the 1.5 GeV/c² mass region and one state of spin, possibly ⁵/₂, in the 1.7 GeV/c² mass region. Some preference was shown for t-channel helicity conservation. The similarity of the data to proton-target results provided independent support for the hypothesis that vacuum exchange was dominant in the production of low-mass double pion states in pp interactions around 20 GeV/c. Members of the group involved in the collaboration were P. C. Bruton, J. K. Davies, S. M. Fisher, F. F. Heymann, D. C. Imrie, G. J. Lush and J. Nassalski.

As already mentioned the Group participated in the WA75 experiment, using a combination of electronic and emulsion techniques at CERN in 1985, which revealed the first example of the hadronic production of a pair of beauty particles, together with their decays into charmed particles, both of which also decayed in the emulsion.

Space Science

The Gassiot Committee of the Royal Society had taken the lead in developing a research programme in atmospheric, including upper atmospheric, physics through its three sub-committes since 1941. The possibility of the exploration of atmospheric structure and the direct observation of solar ultra-violet and X-radiation by means of rocket-propelled vehicles greatly interested British research workers. Following a proposal by Prof. S. Chapman in 1951, the Committee invited the American Upper Atmosphere Rocket Panel to participate in a conference on rocket exploration of the upper atmosphere. Massey, who had become Chairman of the Gassiot Committee in 1951, chaired the small sub-committe appointed to organise the conference. Rather surprisingly, it was left to F. Singer, the American liaison officer in London who was involved in both the scientific and technological aspects of space exploration, to suggest that certain key personnel in the Ministry of Supply, concerned with rocket development, should be invited to attend the conference. This was done immediately and the conference was held in Queen's College, Oxford from 26 to 29 August 1953.

Meanwhile, on the morning of 13 May 1953 when Massey was just preparing to leave his room at UCL for the annual departmental cricket match between staff and students at Shenley, he received a telephone call from a Ministry of Supply official asking whether he would be interested in using rockets from the Ministry for scientific research. Immediately he replied "Yes" and went in search of Boyd and repeated the question! Naturally Boyd welcomed the prospect of the direct application of his probes in the exploration of the ionosphere. He spent two months of the 1953 summer vacation at the Royal Aircraft Establishment, Farnborough gaining experience on the technical side of rocketry. During this period he first met M. O. Robins, who was later seconded to assist Massey in all matters relating to rocket and satellite research. Initially Robins was based in the department, but in the early part of 1963, the small team which had grown up under him, moved to office premises in Chester Gate, Regent's Park, becoming the Space Research Management Unit. In March 1954 Massey was awarded a grant for the employment of G. V. Groves, for one year in the first instance, to undertake preliminary work on rocket instrumentation in the department; Groves had been a Scientific Officer at the Royal Aircraft Establishment and the Headquarters of the Ministry Aviation since graduating at Cambridge in 1948. His experience of rocketry, combined with his ability in theory and practice, proved invaluable, and he was appointed to a lectureship in 1956.

The first experiment, selected by Boyd and Groves, was designed to measure the temperature, density and wind distribution in the atmosphere up to c. 80 km by application of a sound-ranging method, based on a series of 18 explosions from grenades ejected at regular intervals during the upward trajectory of a Skylark rocket. After much experimentation at various locations in the UK, including Shoeburyness, the first successful experiment was carried out at the Woomera range in Australia on the night of 13 November 1957, using ballistic cameras, photoelectric flash detectors and an array of microphones on the ground. The cameras photographed the flashes against the star background enabling them to be located accurately in position; the flash detectors recorded the arrival of light from each grenade flash thereby enabling the times of each explosion to be determined; and the array of microphones recorded the time of arrival of the sound pulse from each explosion at a number of known locations - an array rather than a single microphone being necessary owing to the tilting of the wave front of the sound by horizontal winds and refraction. These data enabled the mean value of the speed of sound between each explosion, and hence the mean atmospheric temperature, and the mean horizontal wind speed to be determined; of course a great deal of analysis was involved, the method being worked out by Groves. In the second experiment on 17 April 1958 grenades exploding above c. 100 km were found to produce a conspicuous bright glow arising from photochemical reactions between the explosion products and atomic oxygen. The glow lasted for about 20 min. and observations of its motion through the air and its rate of expansion enabled the wind speed and the diffusion coefficient of the glow gases through the local atmosphere, which gave an estimate of the local air density, to be obtained. In this way the range of the experiment was extended beyond the 80 km limit set by the background noise in the microphones. On 3 December 1958 there occurred the first successful grenade firing producing a strong twilight glow of sodium vapour ejected from the rocket at an altitude of 100 km. Observations of the Doppler width of the sodium D lines by D. R. Bates (who had suggested the experiment in 1950 - the first suggestion of an active experiment from a rocket) and E. B. Armstrong yielded data on the ambient atmospheric temperature, and those by Groves on the motion of the vapour cloud gave the wind speed. This was the last of seven grenade experiments, which, by good fortune, took place during the International Geophysical Year.

An account of the first grenade experiments at Woomera during 1957-59 was given by Messrs. P. J. Bowen, R. L. F. Boyd, M. J. Davies, E. B. Dorling, G. V. Groves and R. F. Stebbings in Proc. Roy. Soc. Vol. 280, 170, 1964. Almost the entire staff of the department concerned with space research co-operated in the development of the grenade programme until Groves took over responsibility for the whole programme. Further consideration of this aspect of the work is therefore deferred until the section dealing with Groves's Space Science and Atmospheric Structure Group (pp.100-103).

Early on Boyd and Willmore prepared to determine the electron concentration and temperature in the ionosphere by means of a Langmuir probe mounted ahead of the rocket on a four-foot spur to diminish the effect of disturbance by the rocket. They also prepared to measure the intensity of the solar Lyman-alpha radiation by means of the Friedman technique involving a tubular counter containing nitric oxide and provided with a LiF window so that the counter responded to radiation in a narrow band around 121.6 nm. Experiments were also initiated for the measurement of the solar X-ray radiation firstly by means of a photographic method, then with photon counters having different foil thicknesses as windows, and thereafter obtaining higher resolution by pulse height analysis. These experiments were first flown in Skylark rockets in 1959, thus initiating solar X-ray studies by British physicists. In 1960 K. A. Pounds, who had worked on these detectors as a research student, joined the Department of Physics at Leicester University, the head of department, Prof. E. A. Stewardson, an X-ray physicist, having taken a close interest in the work from the start. Thus began a second major X-ray astronomy group in the UK. From the outset there was close collaboration between the two groups. By the end of 1958 several of these experiments were ready for flight, the remainder being in an advanced stage of development.

In March 1959 it was announced that the USA through the National Aeronautical and Space Administration (NASA) would be prepared to launch research satellites for other countries. The offer was taken up by Britain and in December 1959 the payload of the first satellite was planned, taking advantage of experience gained in the Skylark rocket programme. It was largely concerned with observations of the high altitude ionosphere and of solar radiations effective in producing the ionosphere. The UCL group was responsible for five of the seven experiments involved; these including the principal people involved were as follows:-

(i) measurement of electron density and temperature by Langmuir probes (Boyd & Willmore);
(ii) determination of ion composition and temperature by positive ion spectrometer (Boyd & Willmore);
(iii) measurement of solar radiation in a particular waveband by X-ray spectrometer (Boyd & Willmore in association with Stewardson & Pounds);
(iv) detection of solar Lyman-alpha radiation (Bowles & Willmore);
(v) detection of solar aspect angle (Alexander & Bowen).

The probes were operated in the a.c. mode, which has many advantages over the d.c. mode for use in satellites; the properties of the ionosphere were deduced from the first and second derivatives with respect to probe voltage of the current-voltage characteristic, the derivatives being transmitted in real time by the satellite telemetry system. The positive ion spectrometer was of an unusual type depending on measurement of the energy density of the ions relative to the satellite; it took into account the kinetic energy of an ion relative to the satellite due to the satellite's velocity. The satellite was named Ariel 1 on its establishment in orbit by a Thor-Delta launch vehicle from Cape Canaveral, later renamed Cape Kennedy, on 26 April 1962. All of the experiments were successful except (iv), in which none of the three sensors produced any data, presumably owing to an electronics package breakdown. Fortunately this loss was not important since by the time the satellite was launched it was known that the secular variations of solar Lyman-alpha were of negligible ionospheric significance. Despite the setback due to the hydrogen bomb explosion, code-named "Starfish" on 9 July 1962, results were obtained up to 9 November 1964. A total of 11,910 data tapes were received from the tracking and data acquisition stations; from these tapes no less than 3,307 hours of data were successfully processed, representing 595 million data points. The orbit finally decayed and the satellite was destroyed on entering the atmosphere on 24 May 1976.

On 2-3 May 1963, a discussion meeting on the results then obtained was held at the Royal Society under Massey's leadership (Proc. Roy. Soc. A. Vol. 281, 438, 1964). At this meeting Bowen, Boyd, W. J. Raitt and Willmore described their observations of ion composition, the first systematic observations of both the light ions H⁺ and He⁺ and the heavier ions such as O⁺, although earlier observations of He⁺ and O⁺ had been made on separate occasions. Positive ion transition altitudes as a function of solar zenith angle were presented. For O⁺ - He⁺ this is the altitude at which the O⁺ and He⁺ concentrations are equal, He⁺ being dominant at higher altitudes until the H⁺ - He⁺ transition altitude is reached. A large number of systematic observations of this kind were made and proved very useful for the interpretation of the behaviour of the high atmosphere. Bowen, Boyd, C. L. Henderson and Willmore gave an account of measurements with two probes, one located flush with the satellite skin on the spin axis, the other on a boom, c.1.2 m in length, with the normal to the probe surface parallel to the spin axis, but oppositely directed to the normal to the other probe, showing the ionospheric electrons to have a Maxwellian energy distribution, any non-Maxwellian, high energy 'tail' including less than 1% of the total. Measurements of the charge distribution round the satellite were in good agreement with theory, the satellite exhibiting no 'ram' effect, but a very marked depletion of charge was noted in the wake; no associated effect on the electron temperature was detected; and some evidence was found for the occurrence of plasma oscillations in the wake. The electron temperature distribution between 400 and 1200 km was found to be subject to strong control by the geomagnetic field, and to exhibit an increase with geomagnetic latitude and altitude. The daily average temperature was correlated with solar 2800 Mc/s radiation and increased at about the same rate as the neutral gas temperature. Measurements of the solar spectrum in the X-ray wavelength band from 0.4 to 1.4 nm were described by Bowen, K. Norman, Pounds, P. W. Sanford and Willmore. Such observations were of special interest during solar flare disturbances leading to communication blackout through enhancement of ionization and hence absorption at D region heights. Many such observations were made from Ariel 1. The variation of X-ray intensity with wavelength emitted by the sun at different stages of a solar flare showed that at the height of the flare not only was the overall intensity increased, but it extended to much shorter wavelengths. This was the first satellite study of soft X-rays using proportional counters.

Boyd and Susan Laflin analysed in detail the ion mass spectrometric data obtained from Ariel I in its survey of the topside ionosphere over the latitude range of ± 55%. The ion energy spectrometer measurements showed the ions O⁺ and He⁺ to be the major massive components of the ionosphere and enabled a global study of the composition over the northern summer of 1962 to be made. Earlier analyses of parts of the data had shown a diurnal and seasonal variation in the composition, a strong geomagnetic control and a suggestion of a departure from hydrostatic equilibrium in the diffusive separation of the ions. Their definitive presentation of the computer analysis of almost all of the ion composition data obtained by the energy spectrometer, and its regression analysis in terms of geomagnetic latitude, altitude and local solar time, confirmed and strengthened the earlier conclusions. Total ionization density measurements and a study of the effect of vehicle aspect on them were also given.

The notable achievement of Ariel I in making the first world-wide survey of the topside ionospheric composition and temperature, showing the strong effect of the earth's magnetic field and the control of the electron temperature by ionic concentration, was responsible for the invitation to instal similar instrumentation on the NASA ionospheric satellites, Explorer XX and XXXI. Studies by the topside sounder satellite Alouette I had revealed the importance of including equipment to give direct measurements of ion mass spectra and temperatures. Hence a UCL positive ion mass spectrometer was included in the US topside sounder satellite, Explorer XX, launched on 25 August 1964. This provided a large amount of data on the ion composition and temperature of the upper F-region at an altitude of c. 1000 km, and over a latitude range of 80 deg N to 80 deg S. Initial analysis showed that the resolution of the spectrometer was far superior to that flown on Ariel I; the shapes of the peaks agreed much closer with theoretical predictions. Data from high magnetic latitudes showed a marked deficiency in the ion density, further investigation confirming that the onset of ionization when emerging from the region could be very rapid.

Explorer XXXI and Alouette II topside sounder were launched on 29 November 1965 into an 80 deg prograde polar orbit, with a perigee of 500 km and an apogee of 3000km, as part of the ISIS (International Satellites for Ionospheric Studies) programme. An important objective of the mission was to compare the sounder measurements with simultaneous direct ones made at the same position by the satellite in order to improve the understanding both of the techniques involved and the physics of the ionosphere. There were six direct measurement probes on Explorer XXXI: planar ion trap for ion density, temperature, and composition; planar electron trap for electron density and temperature; cylindrical electrostatic probes for electron density and temperature; magnetic ion mass spectrometer for ion density and composition; planar Langmuir plate for electron temperature; and spherical ion probe for ion density, temperature, and composition. The first four were US probes, the last two being UCL ones. Electron temperatures measured by the three different probes generally agreed to within 10%; ion compositions measured by the planar ion trap and the spherical probe showed good agreement with those by the high resolution magnetic mass spectrometer; ion temperatures measured by the ion trap were consistently higher than those by the spherical probe; and plasma densities measured by the various probes generally agreed with simultaneous Alouette II sounder values to within 20%. Measurements of electron temperature, ion composition and temperature by the UCL instruments were compared with corresponding values determined by RSRS from Alouette II ionograms for selected passes 11when the two satellites were close together only seconds apart. Electron concentration measurements by the sounder were used for in-flight calibration of the probe total positive ion concentration measurements, and an effective grid transparency for the probe was obtained. This transparency, apparently different for different ion species, was 38% for hydrogen ions and 42% for oxygen ions. Data were combined with Alouette II scale height determinations to test the adequacy of thermal diffusion theory in the topside ionosphere.

The composition of the ionosphere during the early months of the satellite's life changed from O⁺ near perigee to H⁺ at apogee; He⁺ was not observed as a dominant ion at intermediate altitude as with Ariel I in 1962. However in 1966 He⁺ rapidly reappeared as a major constituent, thereby showing its strong solar cycle variation. The height of transition of ion composition from O⁺ to H⁺ was found to depend markedly on local time, being some 150 km higher during the evening than at early morning, and varying significantly with longitude, but showing little dependence upon latitude up to 50 deg. Observations during a series of six magnetic storms in the first half of 1967 showed that in mid-latitudes, for altitudes up to 1500 km, strong enhancements of electron temperature, of order 800 K, were common, generally being accompanied by depressions of total ion density. This contrasted with earlier observations of Ariel I in which storm temperature enhancements were practically absent. Mid-latitude variations in ion composition showed no consistent pattern; for a storm in February 1967 O⁺ showed an increase of only about 30%, while the light ions increased by up to a factor of 4; in the great storm of May 25, the light ions showed no variation, while O⁺ increased by a factor of 3; and in a storm on 6 June, there was negligible variation in O⁺, but the light ions decreased by a factor of 2. Variations in ion temperature had not then been reliably observed. Simultaneous observations of electron temperature, ion temperature and electron (or total ion) density were made with the Thomson backscatter group in France when the perigee of the satellite was near the latitude of the scatter station at St. Santin. Although the scatter measurements referred to the altitude range, 275-425 km, while the nearest satellite ones were at 550-600 km, the agreement between the extrapolated scatter and Langmuir probe data was excellent. The comparison made clear the necessity for caution in interpreting satellite probe data in terms of altitude profiles in view of the presence of strong latitude variations, since in the comparison the satellite data for 520-540 km were at a higher latitude and showed the the then well-known increase in electron temperature with latitude.

Starting in 1959 with a Skylark rocket launched from Woomera on 8 July, some sixty rockets were involved in experiments on atmospheric, ionospheric and solar physics, and stellar ultra-violet astronomy before the Space Research Group, under Boyd, became fully operational as the Mullard Space Science Laboratory at Holmbury St. Mary at the start of the 1966-67 session. That first rocket, which attained a height of 93 km, carried Langmuir probes to determine electron and ion concentrations, and solar X-ray detectors. The majority were unstabilised Skylark rockets, launched from Woomera in the British national programme, although a low accuracy sun pointing Skylark was included, being flown on 5 May 1966. In the European Space Research Organisation (ESRO) programme two Skylark rockets, carrying electron temperature probes to study the electron temperature in the middle ionosphere, were launched from Sardinia in 1965. In this programme six Centaure rockets were launched from Andoya, Norway in 1966, four carrying positive ion probes to study the fine structure of auroral ionisation, and two carrying ion energy spectrometer probes to study the identification and concentration of ions in aurorae. In the ESRO expedition to Greece for the annular solar eclipse on 20 May 1966 two Centaure and five Arcas rockets were launched from Euboea at various stages of the eclipse, the former carrying electron temperature probes and hydrogen Lyman-alpha detectors to study the electron temperature in the lower ionosphere and the solar Lyman-alpha flux, and the latter carrying fixed potential positive ion probes to study the D-region ionization. Earlier on 15 May two rockets had been fired, a Centaure rocket to study the total solar X-ray flux in the 1-3 Å band, and a prototype Arcas rocket. It was shown that the X-rays rather than the Lyman-alpha radiation were responsible for the ionization. Eight Centaure rockets were also fired from Hammaguir in the Sahara in French co-operative programmes in the study of sporadic E ionization. Positive ion probes were flown in the first pair in 1963, electron temperature probes being added to the second pair in 1964, and to the quartet, which in the 1965/6 winter made altitude profile measurements of electron temperature and density, positive ion density and wind speed.

The first observations of stars in the Southern sky at ultra-violet wavelengths between 1700 and 2000 Å were made by Heddle, Alexander and Bowen during the flight of an unstabilised Skylark rocket launched from Woomera on 1 May 1961. Five 'telescopes', each consisting of 10 cm lengths of aluminium honeycomb, were fixed at different angles in the rocket head. Photocells with sharply peaking sensitivity at c. 1900 Å detected radiation collimated by the telescopes as the rocket rolled and changed attitude during flight. The attitude of the rocket was to be measured by means of a moon detector, a magnetometer, and a camera photographing the star background, but only the records of the moon detector proved satisfactory. Two of the telescopes detected ultra-violet radiation from 22 stars; these were identified and the ratios, in each case, of the flux at 1900 Å to that at 5390 Å was determined.

The proportional counter spectrometer on Ariel I had recorded the intensity of X-radiation from the solar disc in the wavelength range 5-12 Å, and although the occurrence of the solar flare stood out against this background, it could not be localised. The UCL and Leicester teams planned an extensive programme after Ariel I, proposing X-ray cameras as standard auxiliary equipment on each Skylark rocket. In anticipation of sun-stabilised Skylark rocket, they planned to study the distribution of X-ray sources over the sun using a grazing incidence paraboloidal reflector with a suitable detector at the focus.

By 1966 the newly formed Mullard Space Science Laboratory was carrying out or planning experiments on both the neutral and ionized atmosphere, on the magnetosphere, on the quiet and disturbed sun, on aurorae, and on stars in both ultra-violet and X-ray wavelengths. Its programme of instrumental preparation for satellite launchings and rocket firings was most impressive, as is shown by the following table, listing satellite, instrument, and experiment.

OSO-D	Broad-band X-ray spectrometer; total solar soft X-ray flux *  Ultra-violet monochromator; total solar flux of He II 304 Å radiation
OSO-F	X-ray scanning spectroheliograph; solar X-rays from quiet and disturbed regions *
OSO-G	Extreme ultra-violet polychromator; solar 170-1000 Å flux
OAO-C	X-ray telescope; X-rays from galactic sources
OGO-E	Electron temperature probe; electron temperature in magnetosphere
ESRO I	Electron temperature probes & positive ion energy spectrometer; polar ionosphere
ESRO II	Broad-band X-ray spectrometer; total solar soft X-ray flux *
TD2	Extreme ultra-violet polychromator scanning spectroheliograph; solar extreme  ultra violet Ionosphere probes; polar ionosphere

OSO, OAO and OGO are NASA's Orbiting Solar, Astronomical and Geophysical Observatories;
TD 2 is an ESRO satellite; and * denotes collaboration with Leicester University's Physics Department.

Scheduled rocket flights listed in the ESRO programme were six Arcas rounds to study polar cap absorption and D-region ionization; four Centaure rounds, two to study the fine structure of auroral ionization, and two to identify and determine the concentration of ions, and the electron temperature in the lower ionosphere, all fired from Kiruna, Sweden; four Skylark rounds to determine the electron temperature in the lower ionosphere; two Centaure and two Skylark rounds to study the total flux of solar Lyman-alpha radiation, all fired from Sardina. In the British national programme there were three sun-stabilised Skylark rounds, one to study X-rays from quiet and active regions of the sun, and Lyman-alpha radiation, and two to study the solar extreme ultra-violet spectrum, and ionospheric processes in E and lower F-regions, and one moon-pointing Skylark round to study ultra-violet fluxes from hot stars, and stellar atmospheres, all fired from Woomera; five Skua 2 rounds to study the correlation between lower ionospheric electron temperature and geomagnetic fluctuations based on ground magnetometer measurements, and four Petrel rounds to study ionospheric parameters in D and lower E-regions over the twilight period, all fired from South Uist.

Solar X-ray and Ultra-Violet Astronomy

The OSO-D satellite was launched on 18 October 1967 as OSO-4. The UCL/Leicester experiment designed to measure the total X-ray intensity in the 1.3-18 Å and 44-70 Å wavelength bands, using proportional counters developed from those used in Ariel 1, was successful, X-ray emission from the full disc of the sun being observed throughout the seven-year life of the satellite. X-ray bursts associated with solar flares were found to be of two kinds, one impulsive and the other showing a relatively gradual rise and fall. The X-ray flux usually provided the first indication of the start of a solar event, but there was, on average, a delay of two minutes between the peaks of the corresponding microwave and X-ray bursts, the delay being longer the softer the X-radiation. However many X-ray events were found to have precursors and there was evidence that some X-ray activity preceded the microwave. The first evidence for the cooling of flare plasmas by thermal conduction was obtained, a theory of conductive cooling of plasmas in loops being developed by Culhane, K. J. H. Phillips and J. F. Vesechy.

ESRO II, the first satellite constructed under the management of ESRO, was launched on 29 May 1967, but did not attain orbit owing to a failure of the Scout rocket launcher. The back-up satellite, renamed Iris, was launched on 16 May 1968 and carried into orbit a UCL/Leicester proportional counter spectrometer to measure the solar flux in the 1-20 Å wavelength band. After some trouble during the initial switch-on period, the apparatus was switched off until 14 July, when it started to work correctly. Later it continued working in its low sensitivity mode, the high sensitivity mode being affected by ambient plasma conditions at certain parts of the orbit.

OSO-F, later to become OSO-5, was launched on 22 January 1969, carrying into orbit the first of its kind, proportional counter detector, X-ray spectroheliograph. A 3-9 Å counter detecting radiation gathered by a pair of slits, and a 8-12 Å counter, mounted at the focus of a grazing incidence paraboloidal mirror, were used in the scan of the solar disc. This UCL/Leicester instrument performed well and provided data from which the first daily graphs of solar X-ray activity were published by the World Data Centre C at Boulder until January 1973, when they were superseded by higher resolution data becoming available with the launch of OSO 7. The instrument still functioning well, was switched off in July 1975.

The opportunity to improve the space, time and wavelength resolution in order to study individual solar flares in detail came with the opportunity to participate in the Solar Maximum Mission (SMM) planned by NASA to study solar flares during the maximum of the solar cycle in 1979-80. An MSSL group, led by Culhane, in collaboration with an Appleton Laboratory group, led by an old departmental student, A. H. Gabriel, and the USA Lockheed Palo Alto Research Laboratory (LPARL) designed and constructed an X-ray polychromator for one of the two UK experiments accepted for SMM. The polychromator comprised two instruments, namely, a flat crystal spectrometer with fine collimation scanning all atomic transitions important for flare and plasma diagnostics in the wavelength range 0.15 to 2.5 nm, and a bent crystal spectrometer providing simultaneous fixed coverage of the wavelengths in certain important spectral intervals with very good time and wavelength resolution at the cost of broader collimation. SMM was launched on 14 February 1980 and over 50 major flares and many more minor ones were observed by the polychromator until the fine pointing control of the satellite failed in November 1980. Following the in-orbit repair by the crew of the Space Shuttle, Challenger, in April 1984, observations were resumed and continued until the re-entry of SMM after almost ten years in orbit.

In an early sun-pointing Skylark rocket launched on 5 May 1966, K. Evans, Pounds and Culhane measured the intensities of 28 identified and 4 unidentified solar X-ray emission lines in the wavelength band 11-22 Å with two slitless crystal spectrometers. It was possible to derive information about temperatures both in the quiet corona and in active regions from these results, some of the first obtained in this spectral region. This rocket also carried a proportional counter spectrometer placed at the focus of a parabolic mirror to obtain X-ray pictures of the sun in the 8-18 Å wavelength band, as did another rocket, launched on 8 August 1967. Contour maps of the intensity of solar X-radiation made from these spectral heliographic observations showed that, during the interval between the flights, the sun, which had been active in the northern hemisphere only, became active in the southern hemisphere also. The use of proportional counters enabled information to be gained on the change of intensity of the radiation with wavelength for each emitting region on the sun. D. H. Brabben and W. M. Glencross measured spectra in the wavelength band 10-24 Å from three active solar regions with a collimated crystal spectrometer flown on a Skylark rocket, launched on 10 December 1971; strong lines of Fe XVIII, Ne IX, O VII and O VIII were readily identifiable. A more advanced spectrometer was flown on a Skylark rocket launched on 26 October 1972. Instead of using a fixed collimator defining a small area of the solar disc, it used a rotating collimator before the crystal, whose rocking curve defined a strip across the disc, the rotating collimator then locating each emitting region within the strip. The crystal was rotated slowly throughout the flight to explore the whole of the observable corona in the spectral range 6-25 Å. During the flight a small flare commenced in the McMath calcium plage region 12094 and the emission from this provided the major contribution of the observed spectrum in the wavelength range 14.5-17.1 Å. Spectral and spatial observations from a group of active regions in the S W and the small McMath region 12094 were combined to investigate the conditions in both active regions and flare plasmas. Culhane in collaboration with LPARL used a collimated Bragg crystal spectrometer to study the X-ray line spectrum of the solar corona. The first flight of the instrument took place in an Aerobee 170 rocket from White Sands, USA. Temperatures and differential emission functions were obtained for the general corona and for six active regions, and electron densities both in the general corona and the active regions were shown to be less than 5 x 10⁹ cm³. The intensities of the principal satellite lines of O VII or Ne IX were measured and used to obtain the coronal temperature, and the satellite wavelengths were measured more precisely than theretofore. In a further MSSL collaboration with LPARL, a Skylark rocket launched on 30 January 1976, carrying an instrument containing three plane Bragg crystal spectrometers designed to investigate the temperature and emission measure distributions in quiet coronal structure typical of solar minimum, developed a fault in flight preventing the payload achieving fine stabilization.

The UCL, small grazing incidence, monochromator on OSO-4 monitored variations in the absolute intensity of a 10 Å wavelength band of the solar extreme ultra-violet spectrum centred on the He II Lyman-alpha line at 304 Å during periods, October to December 1967 and June 1968 to December 1969. Measurements were also made during these periods of the absolute intensity of the solar H Lyman-alpha line at 1216 Å. The intensity of the He II line revealed long-term variations of up to 20% from the mean value and short-term flux increases of up to 25%, but that of the H line remained essentially constant. Solar activity, measured from the ground, was found to be a poor indicator of the level of the solar extreme ultra-violet flux, the general level of the observed He II Lyman-alpha line intensity following most closely variations in the relative sunspot number.

OSO-G was launched on 9 August 1969, becoming OSO-6. It carried into orbit the extreme ultra-violet polychromator to measure absolutely the total ultra-violet flux of important solar lines from H, He, C, N, O and Fe. During the first six months of the flight, results were obtained for four lines, 304, 537, 584 and 1216 Å; mean fluxes, and daily variations were given and compared with corresponding variations of the 10.7 cm radio flux and Zurich sunspot number.

A grazing incidence spectrograph with a concave grating stigmatised by a grazing incidence toroidal mirror was designed for one of the two ESRO small stabilized, satellites, TD-2. The instrument had a wavelength resolution of 1 Å and spatial resolution of 1' arc and was intended to observe 27 solar lines from 150-600 Å. It was planned to use a small on-board digital computer for data processing, experiment control and the interpretation of telecommands. However in 1968 when it became clear that the completion of both TD-1 and TD-2 would be too expensive, the latter was dropped.

The first experiment involving the simultaneous measurements of related ionospheric and solar ultra-violet parameters in relation to ionospheric theory in the 150-200 km range was carried out by MSSL and Birmingham University in a sun-stabilized Skylark rocket flown on 3 April 1969, an account of the experiment being given on pp.99-100 of the Geophysics section. A joint experiment planned with the Appleton Laboratory involved a Skylark rocket payload consisting of a grazing incidence grating spectrograph designed to determine the He/H abundance ratio in the solar corona as a function of height. The intensities of selected wavelengths in the range 150-1335 Å were to be recorded so that measurements could be made of the resonant scattering from the corona of the Lyman-alpha of H I at 1216 Å and He II at 304 Å. The rocket, the last Skylark launched from Woomera, was flown on 12 May 1978, good observations being obtained with the spectrograph. The experiment was rebuilt in an enhanced payload for the systematic study of hydrogen and helium abundances, temperatures and densities in coronal structures during the second flight of Spacelab in 1985.

Cosmic X-ray and Ultra-Violet Astronomy

Before any evidence of the existence of observable cosmic X-ray sources, the UCL group under Boyd and Willmore had started to design a telescopic system using grazing incidence parabolic reflectors with proportional counters at the foci for inclusion in a satellite to observe cosmic X-rays. They also considered the design of detectors for use in Stage 3 stabilised Skylark rockets as announced in their research plans to the British National Committee in January 1962. Later that year, Scorpio X-1, the first powerful X-ray source, was discovered, and encouraged development in the field. Boyd and Willmore's proposal to include their telescopic system in the payload of the third US astronomical satellite OAO-3, as an auxiliary system to the main ultra-violet observing system, was accepted in 1963, but the satellite was not launched until 21 August 1972. Meanwhile the US satellite Uhuru, the first devoted to cosmic ray astronomy, had been launched in December 1970, leading to the discovery of many new sources, including extended ones, particularly from clusters of galaxies. Thus the launching of OAO-3, thenceforth known as Copernicus, was most propitious, giving MSSL a unique and powerful means for the observation of X-ray sources, galactic and extragalactic, with high space and time resolution. The X-ray telescope, c. 90 cm long, consisted of three reflecting mirror systems, a collimated proportional counter and a star tracker to measure any gross misalignment of the instrument relative to the axis of the spacecraft. Observations were made over the waveband 1-20 Å, the background count, despite care being taken to make it tolerable, prevented them in the range, 20-100 Å. The fields of view of the mirrors could be varied by changing the aperture at each focus. For the 1-3 Å waveband, the field of view of 3 deg was fixed by the collimators, but for 6-18 Å it could be selected to be 2, 6 or 10 min, and for 3-9 Å, 1, 2, or 10 min, the large aperture generally being used for studying time variations in the intensity emitted from a particular source. The initial allocation of 10% of Copernicus's time to X-ray observation was increased to 20% in 1973. Operations from Copernicus were ended at the end of 1980 after 7¹/₂ years of very successful observations.

Copernicus was the first satellite to include an X-ray instrument which could be pointed with high accuracy for extended periods at selected sources. The first observations located the source GX2 + 5 more accurately than theretofore. The second observations were directed to Cygnus X-3, since in 1972 a nearby, weak radio source had suddenly flared up to many times its original strength. No corresponding increase in X-ray emission was found, but it was discovered that the X-ray intensity varied with a period of c. 5 h. The form of the X-ray light curve differed from those of other periodically varying sources in that it was smooth, with the minimum flux near zero, whereas, for example, Hercules X-1 exhibited sharp transitions from high to low with no residual flux at the minima (F. J. Hawkins, K. O. Mason and P. W. Sanford) .

Following on the discovery of compact objects in binary systems by the Uhuru satellite, Hawkins, Mason and Sandford showed that absorption features or 'dips' in the X-ray intensity of Cygnus X-1 occurred at times when the secondary of the HDE226868 binary system was at superior conjunction. These observations confirmed the identity of the X-ray source with the binary system and pointed to the existence of a black hole.

The first detailed maps of the X-ray emission from supernova remnants were obtained by the MSSL reflectors on Copernicus. The structure of Cassiopeia-A was resolved for the first time and maps of the older remnant Puppis-A showed the interaction of the expanding shock with interstellar clouds. X-ray emission was detected in a broken ring at a radial distance of 4 arc min from the centre of the Crab nebula, the origin of the emission, shock heated gas or a halo from scattering by interstellar gas, not being established (P. A. Charles, J. L. Culhane, A. C. Fabian and J. C. Zarnecki).

Many observations were made of extragalactic sources, the most exciting being those of Centaurs-A in 1975, which was found to have increased its X-ray emission by more than a factor of four since its first observation from Uhuru. This was the first discovery of a variable extragalactic X-ray source. Its emission was monitored every few weeks and it gradually settled back towards the original intensity observed from Uhuru (P. J. H. Davison, Culhane, Fabian and R. J. Mitchell).

The first proposal for a cosmic X-ray payload in the Ariel series was made to NASA through the SRC in July 1968. After several revisions, an agreement was reached in 1970 for a satellite code named UK-5, which became Ariel 5 on launching into orbit on 15 October 1974. It contained two experiments devised by Boyd and Willmore, namely, measurement of source positions and X-ray sky survey in the energy range, 0.3 to 30 keV, and study of the spectra of discrete sources in the energy range, 2 to 30 keV. In the former experiment a rotation-modulation collimator was aligned along the spin axis of the satellite. With a known X-ray source in the field of view as a reference, position was determined to 1 min of arc, otherwise the accuracy was c. 10 min of arc. A time resolution of 0.5 min was obtained in the energy range 1.9-18 keV using proportional counter detectors, this being raised to c. 1 min for the low-energy range 0.6-6 keV using electron multipliers as detectors. In the spectral energy range 1.4-30 keV, a multi-wire proportional counter with a beryllium window was used to obtain the best possible spectral resolution for sources in directions close to the satellite axis; the time resolution was 1 min, but it was reducible to a few milliseconds by means of a 'pulsar' mode of operation.

During the first year of operation of Ariel 5, the MSSL rotation collimator experiment observed 8-9 transient sources, many more than expected. They were generally very bright at maximum, Tau-XT (A 0535 + 26), very close to the galactic anti-centre, being the second brightest source observed up to that time, and A 0620-00 in Monoceros being the strongest source in the sky for several weeks. During a transient flaring stage of Cygnus X-1 in May 1975, a phase difference was found between variations of high and low energy flux. Tau-XT, the second brightest source of soft and medium energy X-rays, proved to be the strongest hard X-ray source observed.

The first transient sources observed, lasting weeks to months, were all located close to the galactic plane; later several brief or fast transients, visible for hours or less, were found. The rotation collimator instrument found amongst the first transients observed, one modulated with a period of 6.75 min and a second of period 1.7 min. These were the first slow rotators observed, probably being characteristic of neutron stars in binary systems as distinct from single stars responsible for radio pulsations.

The multi-wire proportional counter experiment obtained X-ray spectra of the supernova remnants, Cassiopeia-A and Tycho, showing emission lines of Fe XXV and allowing estimates to be made of both the ion abundance and the temperature of the shock-heated gas. X-ray bursters, discovered in 1976, were soon observed by the rotation collimator instrument, bursts being seen on every occasion in 1976 when the instrument was pointed close to the galactic centre. High-time resolution studies made on the very strong burster, MXB 1930-335, showed that the bursts, each a few seconds long, came in pulse trains, the pulses within each train having some periodicity, typically of period 15 to 20 s.

Using both the rotation-modulation collimator and multi-wire proportional counter experiments, detailed studies were made of the emissions from some extragalactic sources, including the quasar 3C 273, the strongest extragalactic source, M 87, the Seyfert Galaxy, NC-C4151, and the four bright clusters of galaxies, Virgo, Perseus, Coma and Centaurus. A feature of the spectrum of the Perseus cluster near 7 keV was identified as arising from the K emission lines of Fe XXV and Fe XXVI; similar weaker features were also identified in the spectra of the Centaurus cluster and the source 0627-544. The existence of these lines supported the view that the X-rays arose from a hot plasma, at temperatures of the order of 5 x 10⁷ K. Two X-ray spectra of NGC 415 were obtained one year apart, the second showing a substantial increase in the quantity of absorbing material surrounding the active nucleus of the galaxy; an Fe-K absorption edge was detected for the first time.

Ariel 6, the last spacecraft in the Ariel series, was planned in 1972 mainly to meet the needs of cosmic ray scientists. However it included two X-ray experiments capable of extending the scope of the observations made by Ariel 5. The UCL experiment of Boyd and Willmore was designed to observe very soft X-ray emissions. The satellite was launched on 2 June 1979 but the operation of the X-ray experiments were seriously upset by spurious switching, and inadequate thermal control resulting in the satellite operating outside the expected range of high accuracy attitude sensors for most of the mission.

MSSL was involved with the Cosmic Ray Working Group of the Huygens Laboratory, Leiden and the Laboratory for Space Research, Utrecht in providing the payload for the ESA Exosat satellite. It was responsible for the X-ray detectors for the low energy experiments. Two interchangeable detectors were required to be placed at the focus of each of two Wolter Type I mirrors, one being a position-sensitive proportional counter and the other a position-sensitive channel-multiplier array detector. The resistive-disc readout system developed at MSSL was incorporated in both detectors. It was also involved with the Space Science Division of ESTEC and the Institutes for Cosmic Physics in Milan and Palermo to build a gas scintillation proportional counter (GSPC) as a small 'add-on' experiment for Exosat. The same instrument was also developed for the first flight of Spacelab. The effective aperture was 200 cm2, and the energy range, 2.0-30 keV, with an integrated energy resolution at 6 keV of c. 10%.

MSSL flew two proportional counters of 1000 cm² collecting area on a stabilized Skylark rocket on 11 November 1970 in a successful survey of the centre of the galaxy, the large and small Magellanic clouds and several pulsars for X-ray sources in the energy range, 0.5 to 12 keV. This flight was related to three unstabilized Skylark flights, two in 1970, one on 14 July carrying a rotation collimator, the other on 14 October carrying a rotation collimator and proportional counters, and the third on 7 October 1971 carrying a rotation collimator, so that a large area of sky could be surveyed with good space and wavelength resolution.

The application of lunar occultation methods in determining source positions with high precision was made by both the Leicester and MSSL groups in 1971 when the occultation of the source GX 3+1 was observed by equipment flown on a stabilized Skylark on 27 September (Leicester) and on an unstabilized Skylark on 24 October (MSSL). The source was located to ± 0.5", the most precise location of any cosmic X-ray source.

The first flight of a low-energy X-ray detector, a large thin window, proportional counter, was flown on an unstabilized Skylark on 4 February 1974 by MSSL. A highly sophisticated control system was used to maintain the gas density in the detector within the range, ± 0.15%. The flight established Gould's belt as an X-ray absorbing region and also discovered an absorbing ridge in Hydra.

MSSL also made the first high-resolution detection of an X-ray line from a cosmic source by means of a Bragg crystal spectrometer flown on a high accuracy Skylark, directed to the supernova remnant Puppis A, on 4 October 1974, this being the O VIII Lyman-alpha line at 19 Å (Zarnecki and Culhane). A comparison of this result with a later observation by Ariel 5 allowed a new determination to be made of the distance to this source.

A position-sensitive detector was flown for the first time in a Skylark rocket launched from Woomera on 12 May 1976 to obtain a high-resolution, two-dimensional, X-ray map of Puppis A, this being a collaborative study with Birmingham University and the NASA Marshall Space Flight Centre. A Skylark rocket, launched from the Arensillo range in Spain on 17 July 1976, carried two sets of reflecting crystals feeding one-dimensional, position-sensitive detectors to measure the strengths of the sulphur (2.6 keV) and iron (6.8 keV) lines in Cas A, this being a collaboration with the University of Tubingen. A further collaboration involved LPARL and ESTEC in the construction of an imaging X-ray telescope for a flight in a NASA Aries rocket. The two-dimensional, position-sensitive proportional counter was to be carried at the focal plane of the telescope, with its associated gas system, electronics and ground support equipment, two further models of the GSPC being incorporated.

Involvement in UV Satellites (M & R pp. 146-161 & 355-360)

The Solar and Stellar Astronomy Working Group (SASA) of the British National Committee for Space Research, formed in 1958, was soon involved with the RAE, Farnborough in the design of a satellite with a payload consisting of an ultra-violet spectrometer operating in the wavelength range 1200 to 3000 Å with a spectral resolution of 1 Å. The RAE programme was directed by A. W. Lines, who later became Technical Director of ESRO. By 1962 the attention was directed towards the ESRO programme involving the large astronomical satellite (LAS). By October 1964 the specification of the first primary instrument covering the wavelength range 3500 to c. 1100 Å, extending if possible to 912 Å, was prepared, no details being given about a second smaller primary instrument to make broad band X-ray observations. The UCL group under Boyd and the Culham group under R. Wilson were both well equipped and keen to join the project. As soon as it was clear that proposals for carrying out primary experiments on the LAS would be requested, Massey called a meeting in his room at UCL to initiate concerted action on the matter. It was agreed that a proposal should be submitted to ESRO, involving the Wilson group concentrating on the design of the instrumentation for ultra violet astronomy, with Boyd and Boksenberg at UCL providing the design for a detector for the main payload as well as the instruments for the subsidiary X-ray experiment. The UK consortium presented its proposal to ESRO before the required 15 December 1964, as did a German-Dutch group, both meeting the scientific requirements laid down. A French-Belgian-Swiss proposal was also submitted, but departing from the specification. However it was agreed that contracts should be placed with all three groups to produce detailed designs within six months of February 1965. After some delay in placing the contracts because of uncertainty concerning the launch vehicle, the three groups submitted their final design reports by 31 January 1966, and on 9 May 1966 it was recommended that the UK design be adopted for the first LAS instrumental package with one back-up unit. However by the end of 1966 it was clear that the project would not go ahead on financial grounds, and apparently the scientific and technical effort expended on the payload design would be wasted.

A UK Project Study Group, including Bokensberg, set up under Wilson's leadership, produced a new overall design, the Ultra-Violet Astronomy Satellite (UVAS), with substantial savings. Its scientific aim was restricted to the primary objective of the LAS, namely, high-resolution spectroscopy of bright stars. The 80 cm Cassegrain telescope feeding a Paschen-Runge spectrometer operating in the spectral range 900-3000 Å, in the LAS design was replaced by a 45 cm Cassegrain telescope feeding an echelle spectrograph which was 10-20 times more powerful spectroscopically, thereby permitting relaxed tolerances in the pointing, mechanical and thermal satellite sub-system. The reduction of telescope aperture followed from Bokensberg's proposal to use a television camera as detector; however it would be necessary to develop rugged image tubes operating at ultra-violet wavelengths. The new optical system would only operate efficiently down to 1200 Å. Further economy in design was achieved by eliminating stars of magnitude 8 and 9 from the observing programme thereby saving observing time and reducing the accuracy of the coarse guidance systems from 1' to 10'. The UVAS proposal, when submitted to ESRO in 1968, received a very favourable report, but it was not finally accepted, again on financial grounds.

Wilson then wrote privately to L. Goldberg, Chairman of the USA Space Science Board, outlining the UVAS proposal. The Board passed it on to the Goddard Space Flight Centre for detailed evaluation. Wilson visited Goddard spending a week there in detailed discussions of the project. The Americans proposed that the satellite should be launched into a geosynchronous orbit so that it could be operating more or less in real time as an observatory for the whole astronomical community. It was also proposed to include facilities which, through degradation of the spectral resolution when required to 6 Å instead of the usual 0.1 Å, would permit the observation of faint objects.

Wilson returned, proposing that the UK should join the USA in the new project, then referred to as SASD in the American small astronomical satellite programme. Although a decision was not required until late 1971, the SRC allocated at the end of 1970 £137,000 for participation in full design studies. ESRO joined the project, agreeing to supply the solar paddles and the European operation ground station. NASA undertook to provide the spacecraft, the optical and mechanical components of the scientific instrument, and the US ground observatory and spacecraft control software, while the SRC in co-operation with UCL would provide the television cameras and baffles to record the spectroscopic data, and also for acquisition. The image processing software would be developed jointly by the Appleton Laboratory and NASA. The satellite was to be placed in a geosynchronous orbit over the Atlantic Ocean and operated 16 hours a day from the US ground observatory at the Goddard Space Flight Centre for US sponsored observers, and 8 hours a day for UK and ESRO sponsored observers from a ground station at Villafranca in Spain.

The co-operation between the SRC and UCL had to be a very special one since, just before the project was accepted in all three participating agencies, the senior College administration decreed that no further large grants could be accepted by departments from the research councils owing to the load thrown on the administration in processing and supervising the large expenditures involved. The need to supply Boksenberg, the project scientist for the UK side of the programme, with supporting manpower and expensive sophisticated research equipment was met by Massey making special arrangements with J. F. Hosie of the SRC and J. Saxton of the Appleton Laboratory for the secondment of staff and the loan of the equipment to UCL, no large grants ever being necessary. The only problems were those of shortage of working space, but the overcrowding was suffered owing to appreciation of the importance of the project by all concerned.

The project was approved in the US Presidential Budget of 1973/4, its name having been changed to the International Ultra-Violet Explorer (IUE); the SRC and ESRO also approved it at about the same time. In May 1975 Wilson, then Perren Professor of Astronomy, was appointed project director of the UK side of the IUE, nominally on a half-time basis, with the full-time assistance of P. Baker of the Appleton Laboratory. The SRC management team under Wilson took over the responsibility for the assessment and measurement of the properties of the ultra-violet to visible converters, delivered from ITT in the USA, for the bonding of the converters to the Videon tube, and for their delivery to MSDS, a branch of GEC at Portsmouth, with a list of the optimal operation parameters. In 1975 a further SRC grant of £658k was allocated to the IUE work, the contributions from NASA, ESA and SRC being £36m, £9.5m and £4m respectively. By the introduction of three shifts a day, seven days a week working at MSDS, the flight cameras were delivered to NASA by 30 November 1976, and IUE was launched successfully on 12 January 1978. The excellent facilities for astronomical research provided by IUE was soon appreciated, astronomers from 27 different countries using them during its first three years of operation.

The ultra-violet scan experiment, proposed by the Royal Observatory Edinburgh and the Institut d'Astrophysique of the University of Liege, as a major experiment for the first three-axis stabilised ESRO satellite, TD-1, involved operation of the satellite in full sunlight, and this required the design of a baffle system reducing the intensity of sunlight at the detector by a factor of 10¹⁷.

ESRO placed a contract with a small company, formed by some members of the UCL physics department, of which Boksenberg was chairman. A Monte Carlo method of ray tracing was devised and used to work out a suitable design. The entire success of the project depended on this work, which could not be checked in the laboratory; in the event it proved completely successful, thanks especially to Esten's contribution. The design, development and production of the main scientific payload was far behind schedule in 1968, so Wilson, Boksenberg and others, involved in the planning of the LAS and engaged in other ultra-violet astronomical activities, were called in to restore the position. The spectrometry was improved by Boksenberg's suggestion that simply by opening up the entrance slit of the spectrograph, advantage could be taken of the passage of the stellar image across the slit due to the satellite motion to cover the 1350-2550 Å wavelength range by observation in effectively 61 rather than 3-4 channels, thereby greatly increasing the wavelength resolution. When TD-1 was successfully launched on 9 March 1972, the now joint UK-Belgium experiment functioned very well.

The first record of ultra-violet radiation from stars in the Southern sky by Heddle and his collaborators at UCL in 1961 has been described on p 90. Further unstabilized rocket flights were carried out by the UCL group, the last broad band observations being made on 14 July 1965. The equipment comprised a cluster of three photomultipliers, each sensitive to a different band in the region 1,450 to 2,800 Å, set at the focus of a 13_ inch telescope mirror aligned along the rocket axis. Aspect data were provided by a highly redundant system of moon detectors, airglow horizon detectors and magnetometers. Thereafter work commenced on a telescope-spectrometer aiming at a resolution of 0.1 Å in the region between 2,000 to 3,000 Å carried by Skylark moon pointing stabilized rocket. The work then entered a new phase, involving collaboration with the SRC Astrophysics Research Unit (ARU), Culham Laboratory. Two forms of instrumentation were planned, one for the observation of single stars and the other for observation of star fields. The former was based on a Cassegrain telescope, employing a large, forward-viewing primary mirror, fitting into the Skylark conical nosecone. The optical design of a spectrometer with a resolution capability of 0.1 Å was carried out at UCL using a computer ray tracing programme. The spectrometer used an echelle grating of high dispersion crossed with a conventional grating of low dispersion to produce a cyclic spectrogram in a rectangular format covering the range 2,000 to 3,000 Å, the spectrogram being detected by the EMI 9677 UV vidicon tube. The latter used a concave grating in a Wadsworth mounting operating as a dispersing objective to obtain star spectra in the range 900 to 1400 Å over a field of 2 deg x 2 deg. A ray-trace computation showed that the inherent resolution capability of an instrument using a 600 lines per mm, 10 cm by 10 cm grating of 2 m radius of curvature was better than 1 Å over the wavelength range and angular field considered, a pointing noise of 10 arcsec degrading this to c. 2 Å. Two star-stabilized Skylark rockets were launched from Woomera, one on 11 February 1970 for ESRO and the other on 16 June 1970 in the national programme, each payload comprising a cluster of three objective grating spectrographs covering the range 900 to 2300 Å with a spectral resolution of c. 0.5 Å. Each spectrograph had a 2400 lines per mm concave grating in a Wadsworth mounting, the optical design being optimised by the computer ray-tracing technique, and used photographic recording.

Geophysics

OGO-5, the Orbiting Geophysical Observatory, was launched into a highly elliptical orbit on 4 March 1968, MSSL providing one of the twenty-six experiments on board. It was designed to measure the electron temperature and concentration within the magnetosphere, and in the solar wind when the concentration was high enough, by means of a spherical Langmuir probe on an extendable boom, two metres from the main body of the spacecraft. The probe, of greatly increased sensitivity, was operated in the a.c. mode, measuring electron densities in the range from 10 to 5 x 10⁴ cm^-3, and electron temperatures from 10³ to 2.5 x 10⁴ K.

ESRO I, renamed Aurora, was launched on 3 October 1968 and its performance was so satisfactory that the back-up model for ESRO I, renamed Boreas, was launched on 1 October 1969 with a similar payload. They carried out the first satellite study of the anisotropy of the velocity distribution over auroral regions, and indeed globally, due to the presence of the earth's magnetic field.

ESRO TD-2 was cancelled, but the intended further version of the experiments, carried out on Explorer XXXI, were undertaken on the rescue satellite, ESRO IV, launched on 22 November 1972.

The electron temperature probe, modified to operate in the very low electron densities in and beyond the plasmasphere, worked satisfactorily after its deployment on OGO-5 on 7 March 1968. Within the plasmasphere, where the Debye length was short compared with the distance between probe and spacecraft, the properties of the ambient plasma could be measured, but when the electron density fell below 10 cm^-3 the current to the probe was predominantly due to secondary electrons from the probe and spacecraft surface. An analysis of the probe response outside the plasmasphere, with other measurements on the spacecraft, produced good results on the interaction of the spacecraft with its environment and the population of energetic electrons within the magnetosphere. They indicated that photoemission from the probe itself dominated when it was in direct sunlight, but when it was shadowed by other parts of the spacecraft the electrons reaching the probe were secondaries from the impact of higher energy electrons on the spacecraft surface, the secondary electron flux correlating well with incident electron energies in the 0.5-1 keV range.

The energy distribution of electrons from the gold surface of the probe was measured and found to correspond approximately with a Maxwellian distribution of most probable energy, 1.1 eV, but with a significantly higher energy tail. Measurements were made of the distribution of electrons in the outer magnetosphere, particularly those with energies less that 1 keV, and the convection pattern of low energy particles. They were extended to include the connection between the changes which occurred during magnetic storms and observations of ground-based magnetograms; in particular, a good correlation was obtained between thinning of the plasma sheet and the onset of magnetic substorms. Other studies included the variation of spacecraft potential within the magnetosphere, the properties of thermal electrons within the plasmasphere at altitudes above 1000 km, and the mapping of the plasmapause boundary.

The Boyd-Willmore a.c. probes were flown in seven satellites launched during the 1962-72 decade, namely Ariel I (26 April 1962), Explorer 20 (25 August 1964), Explorer 31 (29 November 1965), OGO 5 (4 March 1968), ESRO IA (3 October 1968), ESRO IB (1 October 1969) and ESRO 4 (22 November 1972), as well as in many rockets. Wrenn, D. H. Clark, Raitt and H. C. Carlson made a comparative study of ionospheric electron temperatures measured by the a. c. (modulation) Langmuir probes on Explorer 31 and ESRO IA and various incoherent backscatter radar stations and found good agreement between them. Previous comparisons by Carlson and J. Sayers between satellite d.c. (slow-sweep) probe, T_es, and radar, T_er, electron temperature measurements had fitted the simple linear relationship:-

T_er = 5/6 T_es - 400 K. The discrepancy between modulation and slow-sweep probes, typically 20% on Explorer 31, could be due to work-function drift during a slow sweep. Differences of 50-80% observed in electron temperatures measured by slow-sweep probes and incoherent scatter radars suggested additional sources of discrepancy, such as, temperature anisotropy, effect of fine structure, and a possible non-Maxwellian distribution function for the electrons.

The Langmuir probe technique was frequently applied to study the morphology of electron temperature in the topside ionosphere. Clark, Raitt and Willmore were the first to report a synoptic study of results taken near the sunspot maximum and providing new evidence on night-time heating effects, and day-time heating at high latitudes by low energy particles penetrating the clefts in the dayside magnetosphere. It was based on measurements from the a.c. probe experiment of the magnetically orientated, ESRO IA, taken between October 1968 and April 1969. During this period, over one million independent temperature estimates were obtained, and then used to determine variations of temperature with geomagnetic latitude, local solar time, altitude, and magnetic activity condition. The probe experiment used two plane circular collectors, one remaining parallel, and the other perpendicular, to the direction of the local magnetic field. The observed anisotropy of electron temperature, measured parallel and perpendicular to the magnetic field, most pronounced near local midnight, was strongly influenced geomagnetically; no theory fitting the geometry of the observations in the two hemispheres was given. The study of Wrenn, Clark, Raitt and H. C. Carlson showed that the electron temperatures measured perpendicular to the magnetic field were in essential agreement with radar measurements, whereas those measured parallel to the field significantly exceeded them.

Raitt presented measurements of thermospheric electron temperatures made by the probe experiment on ESRO IA before, during, and after the large geomagnetic storm of 31 October to 1 November 1968. The data covered a complete time sequence over a period of nine days while the satellite covered the altitude range 280-1500 km and remained in the noon/midnight local time zones. They clearly showed the development of enhanced temperatures at mid-latitudes associate with stable auroral red arcs in the midnight time zone, traced the latitude dependence of the heating during the progress of the storm, and showed the persistence of the zone of elevated temperatures after the magnetic activity had declined. The heating of electrons in the noon time zone was not observed to follow the same pattern as that in the midnight time zone.

The ESRO-4 satellite was launched into a near polar orbit (88.9 deg) of apogee 1177 km, perigee 245 km on 22 November 1972 and yielded excellent ionospheric measurements until its re-entry on 15 April 1974. It carried six experiments, including the MSSL one to measure the temperature and density of the major thermal ions in the topside ionosphere up to 1100 km, and in addition the thermal electron density and temperature, and fluctuations in the total ion density. A three-probe system was used, namely, a major spherical gridded probe, with swept potential, collecting positive ions; a subsidiary Langmuir probe measuring electron temperature and vehicle potential; and a subsidiary, fixed potential, spherical probe collecting positive ions.

Dorling and Raitt used the thermospheric electron temperature measurements at altitudes between 250 and 1100 km to derive model functions of electron temperature in terms of altitude, magnetic latitude and local time for the periods November 1972 to June 1973, and March to October 1973. They were compared with those obtained from similar instruments on Ariel-1 in 1962, ESRO-1A in 1968-69, and from ground-based observatories. The models reproduced the major features of topside electron distributions, namely, midday temperatures exceeding midnight temperatures by c. 500 K, dawn enhancement leading to peak temperatures greater than midday values particularly around 50 deg magnetic latitude, and temperatures increasing with altitude at all latitudes and with latitude at all altitudes. The daytime mid-latitude temperature was used to complete a series of observations by various techniques over a solar cycle and thereby confirmed the sense and degree of solar cycle control on the thermospheric electron temperature predicted by theoretical considerations.

The most comprehensive study of topside ionospheric irregularities from direct probe measurements revealing new evidence on possible production mechanisms was carried out by Clark and Raitt. The total ion current probe monitored thermal plasma density variations in the range ± 30% of ambient density with a spatial resolution of about 1.5 km. Latitudinal, diurnal, and altitudinal characteristics of density irregularities in the topside ionosphere were investigated using the 2 x 10⁸ total ion current values recorded during the lifetime of the satellite. The morphology of topside irregularities was dominated by the high-latitude zone evident throughout the day, with the appearance of a distinct sub-auroral zone at night. Significant mid-latitude irregularity occurred at low altitudes at night.

Raitt and Dorling used the data from the thermal plasma probe to study the altitude, latitude, local time variations of H⁺ density during the northern hemisphere summer of 1973. The form of the latitudinal variation was interpreted in terms of one region of H⁺ inflow and outflow within the plasmasphere dependent on local time, and another region of continuous outflow polewards of the plasmasphere, and the role of O⁺ density, as an additional control of H⁺ density, was discussed. The observed variations of H⁺ density in the altitude/latitude plane were used to show the latitudinal transition from low to high speed flow, and the location of the mean plasmapause was defined in terms of the physical processes equatorwards and polewards of the plasmapause.

Raitt collaborated with U. von Zahn (Bonn University) and P. Cristopherson (Kiruna Geophysical Institute) in a study of the magnetosphere-ionosphere-atmosphere interaction at middle and high-latitudes during magnetic storms. Three main effects were observed during increased magnetic activity, namely, a general increase of N2 density over the whole polar cap, but with no clear ionospheric effect; an enhancement of N2 density in the region of the nightside mid-latitude trough with an abrupt termination of the trough on the poleward side by local ionization due to to measured low energy electrons; and the formation of a narrow region of enhanced electron temperature and N2 density, with reduced electron density, in the vicinity of the dayside cusp region. Further collaboration with Bonn involved the depletion of F-region ionospheric density and its relation to the enhancement of N2 densities measured by the Bonn instruments. The reduced data from the MSSL ionospheric instruments on ESRO-4 continued to be the primary source of thermal plasma measurements for an on-going programme of research mainly directed to studies of magnetosphere-ionosphere-atmosphere coupling. Global models of electron temperature and density were developed providing realistic average properties of the electron component of the topside ionospheric plasma, the lower boundary of interactions between the solar wind and the earth's immediate environment, acting through the magnetosphere.

Adrienne and J. G. Timothy and Willmore, with J. H. Wager of Birmingham, studied the ion chemistry and thermal balance of the E and lower F-regions of the daytime ionosphere in a sun-pointing Skylark rocket launched from Woomera on 3 April 1969. Although the importance of simultaneous measurement of related ionospheric and solar parameters was realized by that time, this experiment was the first one to attempt such measurements relating to ionospheric theory in the 150-200 km range. The payload was designed to measure (i) absolute solar flux in the waveband 80-1050 Å with a resolution of 10 Å by a scanning extreme ultra-violet spectrometer, (ii) atmospheric extinction profiles of five strong lines in the solar extreme ultra-violet spectrum by a fixed extreme ultra-violet spectrometer, (iii) the electron temperature by spherical and plane Langmuir probes operated in the a.c. mode, (iv) the total positive ion density by a fixed potential spherical probe, (v) the ambient electron density by a capacitance probe. MSSL provided the instruments in (i) to (iv), Birmingham that in (v). Good agreement was obtained from electron density measurements by the capacitance probe and a ground-based ionosonde close to the launch site. Neutral atmospheric densities and temperatures were derived from the spectrometric data, and ion production rates were obtained from the absorption of solar EUV radiation in the 100-270 km range. Individual ion densities and ambient electron temperature were then calculated on the assumption of quasi-static equilibrium. The effective loss coefficient over that altitude range was 1 x 10^-7 cm³ sec^-1 at 120 km and 2.2 x 10^-3 cm³ sec^-1 at 270 km. Above 130 km the calculated total ion density agreed with the measured density to 30%, but below this altitude it diverged, becoming twice as low at 120 km. The measured electron temperature was greater than the neutral temperature at all altitudes in the 120-270 km. range. The thermal imbalance was explicable on the basis of the measured solar EUV heat input at all altitudes above c. 140 km; an additional heat source was necessary to account for the thermal anomalies at lower altitudes.

Following the observation of a narrow shelf of ionization at an altitude near 100 km due to the presence of sporadic E ionization in the fifth Skylark rocket fired from Woomera on 19 June 1958, much effort was devoted to exploring the phenomenon. UCL introduced a simple fixed potential, positive ion probe, which was flown as a 'piggy-back' experiment on many occasions. Measurements of wind shear, and electron temperature by means of the type of probes developed for Ariel 1, to look for the effect of electric fields, were also included. A collaborative payload of a Skylark rocket fired from Woomera on 2 March 1971 contained two MSSL positive ion probes, a Radio and Space Research Station (RSRS) rubidium vapour magnetometer, RSRS and Birmingham electric field probes, and UCL barium and trimethyl aluminium (TMA) release canisters. The rocket was fired at twilight so that the drift of the vapour trail from the TMA could be photographed from the ground. Ion density profiles on the upward and downward trajectories of the flight clearly showed a sporadic E layer, with peak near 10⁷ km altitude. The vertical ion velocity calculated from the wind velocity, observed from the TMA trail, showed a minimum close to 10⁷ km, but no change of sign. However the electric field, obtained from barium release observations and concordant measurements by the two electric field probes, contributed significantly to the vertical velocity of the ions, the combined effect of wind and electric field showing zero vertical velocity at 107.6 km, and hence the necessity of taking into account both the effects of electric fields and neutral winds.

Following work on the detection and measurement of low energy suprathermal electrons by means of magnetically screened hemispherical analysers, a Skylark rocket was launched from Kiruna on 13 October 1972 into a strong aurora to investigate particle fluxes in the energy range 2-30 eV and resulted in the successful detection of fine structure in the electron flux. There followed three co-ordinated Skylark flights from Andoya forming part of the UK High Latitude Campaign in October-November 1973 to gain a better understanding of the mechanism of the auroral substorm, the range of the analysers being extended to 500 eV. J. J. Sojka and Raitt obtained calibrated energy spectra in all three flights over the range 5-500 eV. These were compared with values calculated from their production as secondaries by the energetic electrons measured in the same flights by RSRS and Southampton University and good agreement was obtained for primary electrons of energy greater than 1 keV. Strongly field-aligned pitch angle distributions were seen on the first flight at altitudes from 200-27 km and energies from 5-500 eV. Four improved detectors measuring electrons and positive ions in the energy range 5-500 eV were flown on the first three-stage Skylark 12 ever launched, and it achieved an altitude of 715 km over Andoya on 24 November 1976, covering an altitude and latitude range normally only associated with satellites while retaining the much greater spatial and temporal resolution of sounding rockets. The flight crossed a stable auroral arc, approximately 100 km thick, just before apogee. A substantial amount of diffuse aurora was crossed before the arc was reached, and after emerging from the arc on the poleward side intense bursts of suprathermal electrons were encountered. The detectors were flown later on the ESA magnetospheric observatory satellites, GEOS I and II, launched on 27 April 1977 and 14 July 1978 respectively.

Finally it should be recorded that Prof. Boyd was created Knight Bachelor in the Queen's Birthday Honours in 1983.

Space Science & Atmospheric Structure Group

As recorded above, almost the entire staff of the department concerned with space research in 1962 co-operated in the development of the grenade programme. Groves then took over the responsibility for the whole programme to determine the temperature, pressure, density and wind speeds in the atmosphere at heights up to c. 85 km at Woomera (31degS), the programme benefiting "very much from his skill both in theory and in the analysis of complicated and extensive data, as well as his ability to plan and carry through the technological side of the work" (M & R, p.273).

He built up a thriving group in the mainstream of research into atmospheric structure, making major contributions both on the experimental and theoretical sides, and carrying out pioneering work in the deduction of data on atmospheric properties from the analysis of satellite orbits. Groves also played a full part in the international organisation of space research and was one of those who produced the first International Reference Atmosphere through the Committee on Space Research CIRA).

He also introduced a course for the College Diploma in Space Science (one year full-time, two years part-time). All postgraduate students joining the group took the course in their first year. It was in two parts:-
General: atmospheric structure, ionosphere, magnetosphere, solar-terrestrial relations,
meteors, interplanetary space, moon and planets, stellar and planetary orbits.
Theoretical and Research: numerical analysis and computer programming, satellite dynamics,
gravitational fields, charged particle motion, selected research topics.
A dissertation on a selected topic was prepared during the third.

28 grenade experiments using the Skylark rocket were carried out at Woomera with the co-operation of members of the Australian Weapons Research Establishment (WRE). The results of a series of 21 of these experiments during 1957-63 were collected together and the variations in temperature, pressure, density and wind velocity were analysed and shown at height levels of 30(10)80 km by Groves. Seasonal variations in W-E wind, in pressure and in density from 30 to 80 km, and in temperature from 30 to 50 km were compatible with a general seasonal model (evaluated for latitude 31degS), apart from the autumn and winter months where slightly larger temperature variations were found at 40 and 50 km, apparently owing to the model being based on measurements taken at different times and different sites, thereby leading to a smoothing of the seasonal effects. The scatter in measurements of all parameters increased with height, a similar increase in the four measurements made on the night of 15-16 October 1963 (see below) indicating some diurnal origin. Measurements of the S-N wind showed a positive bias at 50 and 60 km from October to May, general considerations suggesting a diurnal origin. This was investigated by examining summer S-N flow in 938 launchings mostly carried out within the USA Meteorological Rocket Network. It was found that a diurnal variation with local time was present with a maximum S-N component of c 8 m s-1 occurring at 50 km and close to local noon. An analysis of seasonal variations between 30 and 80 km was prepared for the CIRA.

Height profiles both of temperature and wind speed derived from seven grenade flights during 5 March to 4 December 1962 showed oscillations particularly at the higher altitudes. These were important in connection with diurnal and semi-diurnal variations associated with atmospheric tidal phenomena, and led to experiments being undertaken at closer intervals of time and with successive explosions as near as possible. During the night of 15-16 October 1963 four rockets were successfully launched at local times of 19.21, 21.16, 00.39 and 04.52 hr, the first and last firings being timed for twilight conditions. The use of double grenade bays and some smaller grenades enabled the average spacing between explosions to be reduced to c. 4 km. This remarkable achievement resulted in height profiles of the S-N and W-E wind components showing a clear oscillatory character particularly above 50 km and exhibiting a regular change with local time. Finally on the night of 29-30 April 1965 seven Skylark rockets were launched each containing 36 grenades programmed for ejection at c. 3 km. Although the first and last, launched at local twilight and dawn, were unsuccessful, good results of winds and temperatures were obtained from the other five. The resultant height profiles of temperature, except that from the second flight, were all of the characteristic form showing oscillations becoming more marked at the higher altitudes and varying with time in at least a semi-regular way. Height profiles of the components of wind speed obtained from acoustical observations below 88 km and glow cloud tracking between 90 and 140 km were oscillatory in character, the amplitude of oscillation being much greater above 90 km.

To elucidate the regular features of the upper atmosphere such as the general circulation and tidal oscillations many more launchings were required at different locations. Groves and his group were involved in launchings at Sonmiani in Pakistan in a collaborative programme between NASA, the British National Committee for Space Research (BNCSR) and the Pakistan Space and Upper Atmosphere Committee (SUPARCO) during the International Quiet Sun Year; at Thumba in India as part of the Commonwealth Collaboration; and at the ESRO ranges at Sardinia and Kiruna in Sweden. The rockets involved varied from the Petrel, capable of reaching c. 150 km, to the Skylark and Nike-Tomahawk, capable of achieving an apogee greater than 300 km. The work included payload preparation and testing, development of ground observational equipment, complex data handling and computer analysis, and extensive collaboration with research groups in the various countries concerned. At Sonmiani, for example, the group provided all the special ground equipment, including microphones, cameras and flash detectors, and trained the Pakistan personnel in the acquisition and reduction of the meteorological data and in the operation and maintenance of the equipment, and provided continuing technical assistance in such operation and maintenance.

Although the group contributed to the study of atmospheric tidal oscillations by grenade firings at many geographical locations, they only provided a small fraction of the data required. However Groves undertook the task of analysing a much greater volume of data, discussing his results in a Royal Society review lecture of atmospheric tides (Proc. Roy. Soc., 351, 437-469, 1976). Data from the co-ordinated series of grenade flights carried out by NASA at Wallops Island, Natal (Brazil), and Kourou ( French Guiana), and the greater volume of Meteorological Rocket Network data provided by observations of wind speeds up to 60 km above North America and adjacent oceanic areas were included with particular reference to tidal theory. He also worked on the vertical structure of atmospheric oscillations formulated by classical tidal theory, including the effect of heat sources and gravity. "As a result, a much more detailed and reliable understanding of the phenomena which, though studied in some detail as early as 1898, presented difficult problems of interpretation which still remained until information from space techniques has been forthcoming" (M & R, p. 277).

The first two grenade experiments at Somniani were carried out on 29 and 30 April 1965, Nike-Apache rockets carrying payloads manufactured in the USA; 9 out of 12 grenades were ejected and flashes recorded at four stations in the first experiment, but only two flashes were recorded in the second. A payload containing 25 grenades designed by AWRE, Aldermaston, together with a parallel payload section designed by the Air Force Cambridge Research Laboratories for generating a trail release of trimethyl aluminium (TMA), was used on the next 3 launchings carried out on 24, 27 March and 26 April 1966. Chemiluminescent reactions between TMA and the ambient atmosphere produced a glow enabling measurements to be made of winds and temperature, the analysis of which provided some information on the near equatorial atmosphere, for example, the altitude profile of atmospheric temperature showed two maxima in Spring and changed markedly during a 72-hour period; the meridional component of wind speed above 55 km showed marked diurnal changes confirming earlier observations; and the principal maximum in wind speed occurred at 105 ± 5 km, being a little less than 100 m s^-1 towards NW in Winter and near 118 m s^-1 towards E or NE in Summer at that altitude. "This campaign showed that the combined grenade-TMA technique could be used very effectively in a co-operative programme" (M & R, p.171).

The first grenade experiments at Sardinia were carried out on 30 September and 2 October 1965 after Groves and his group had prepared the ground equipment. Two boosted Skylarks were launched, glow clouds and TMA trails being photographed against the background of stars of Canis Major and Orion to determine camera orientation.

The multiplex system for acoustical recording in which signals from a widely-spaced array of hot-wire microphones were transmitted to a central recording point proved to be one of the most accurate methods of measuring wind velocity and temperature in the upper atmosphere below 100 km. A technique for achieving minimum line noise was developed by R. W. Procunier; each microphone was associated with a control frequency in the range 595 to 2975 Hz, amplitude modulated by the pressure variations. Tests of the prototype equipment at the USA Eglin Air Force Base and at the ESRO range in Sardinia in 1965, where detection was extended to 107 km, led to the development of a unit for extended use at the ESRO range at Kiruna.

The first grenade experiments at Kiruna took place on 1 and 4 February 1968, Groves organizing the supply of the ground equipment. Two Centaure launchings with TMA release were successful, wind velocity and temperature measurements being made up to 90 km acoustically and up to 150 km optically. Although the ground temperature fell to -45 C no major operating problems arose. However the performance of the acoustical recording system deteriorated over three weeks, leading to modification of the system involving component substitution and improved heat insulation for the second two launchings at twilight on 15 October and 1 November 1968. The experiments were carried out in collaboration with ESLAB, the launch times being co-ordinated with NASA grenade launchings at Wallops Island, Fort Churchill and Point Barrow.

Four Nike-Cajun rockets carrying grenade and TMA payloads were launched between 17 and 25 January 1969 from Kiruna to measure wind and temperature profiles in the stratosphere and mesosphere during a stratospheric warming. A stratalert had declared a stratospheric warming over central and south eastern Europe on 16 January and a weak warming still existed over central Asia on 25 January. A cooling of about 45 K at 40 km was observed as anticipated, but at 70 km a warming of about 50 K was noted. Thus a mesospheric warming appeared to follow a stratospheric warming with little variation of temperature occurring at 65 km. Wind speeds of 220 m s-1were observed on 19 January, some of the highest ever recorded in the stratosphere. These launchings were made in collaboration with the Meteorological Institute of the University of Stockholm and the Swedish Space Technology Group and were co-ordinated with six other grenade launchings from northern hemisphere locations, two each from Wallops Island, Fort Churchill and Point Barrow, and three meteorological sonde launchings from South Uist, Hebrides. A. F. D. Scott was in charge of this investigation.

The most effective method of studying the temperature, density and wind structure of the atmosphere above 100 km involved ground-based observations of glow clouds produced at chosen altitudes. A good illustration of the method was provided by the launch of two Skylark rockets from Woomera under twilight conditions on the morning and evening of 31 May 1968. Chemiluminescent reactions between TMA released as a trail between 80 and 140 km in the Earth's shadow enabled the trail to be photographed, its drift giving the atmospheric wind profile, and high resolution photography of the lower trail yielding information on atmospheric turbulence. Four standard 0.45 km grenades were released in succession in the trail, and charges of 5, 25 and 45 kg of high explosive were detonated on the ground, about 1 km downrange of the launcher, at such times that the shock waves produced by them reached the trail shortly after it was formed at altitudes near 100 km, the velocity of the shock waves produced by them giving the temperature of the ambient atmosphere. This was the first time that the propagation of shock waves from grenade detonations in the 90-130 km region was studied optically to derive the temperature from the sonic velocity. Standard aluminised grenades were released at intervals between 150 and 240 km above the Earth's shadow, multiple releases above 190 km maintaining a nearly constant surface intensity; the AlO produced resonantly scattering the sunlight. Time-sequenced photographs of the AlO clouds enabled the diffusion coefficient and neutral winds to be determined, spectroscopic observations of the band structure of the resonant radiation at c. 2 Å resolution enabling the temperature to be determined. A dynamic picture of the interactions of atmospheric structure was constructed from the co-ordinated series of measurements of neutral atmospheric wind velocity, turbulent structure, temperature and density made during each launch between 90 and 250 km altitude. D. Rees collaborated with Messrs. R. G. Roper, K. H. Lloyd and C. H. Low (WRE) in this work, applying different observational methods and experimental techniques developed by their groups (Phil. Trans., Roy. Soc., Vol. 271. 631, 1972).

In a collaboration with workers from the Appleton Laboratory, WERE and the University of Brisbane, Rees and M. P. Neal showed in 1972 that a lithium glow cloud could be used to determine the wind distribution in sunlight. A Skylark rocket released the lithium at an altitude of c. 200 km, daylight observations of the glow being made by a differential photometer and also by a Fabry-Perot plate with a resolution of 1.0 Å together with an interference filter of 3.0 Å band pass around the lithium resonance line. The glow cloud was observed for 20 minutes and from its motion the wind speed of 32 ± 2 km s-1 in a direction specified by an azimuthal angle of 221 ± 2 deg was measured at 202 km. Frequent applications of the lithium glow technique followed this successful flight. A notable example involving the group, under the leadership of Rees since 1974, took place at Thumba during February 1975 in which it was planned to launch 12 rockets in one day between dawn and dusk to investigate atmospheric and ionospheric processes including neutral winds and the equatorial electrojet. In the event five Petrels were launched on 9 February, four being successful, the fifth only partially so. Measurements were made of neutral winds and temperature at dawn by means of TMA trails and in daytime using lithium vapour trails; of electron density and temperature; and of electric fields. On 19 February two further Petrel flights measured wind distribution at dusk and daytime, and two Centaure flights, one completely successful, measured electron density and temperatures, and electron currents using a scalar magnetometer, and the other, mainly successful, measured electron currents with a vector magnetometer. Rees collaborated with scientists from the Indian Space Research Organisation and the University of Birmingham in these experiments. (M & R, p. 175 ).

To extend measurements of night-time winds above 150 km, the normal limit of a TMA trail, the group in collaboration with the Appleton Laboratory developed a mobile tuned dye laser radar system for tracking sodium clouds. It was first operated successfully by Rees and M. C. W. Sandford, of the Appleton Laboratory, during the High Latitude Campaign at Andenes, Norway in October and November 1973, the experiments indicating that the laser radar system could obtain wind profiles from sodium clouds at over 300 km, the predicted design limit.

Rees developed an ultra-stable single etalon, Fabry-Perot interferometer to make direct observations of the line profiles of airglow emissions in order to obtain wind speeds and temperatures in the thermosphere. A successful trial in a balloon experiment observing atmospheric absorption lines of H2O and O2 led to the etalons being incorporated in an instrument developed with the University of Michigan and launched on 3 August 1981 as part of the NASA Dynamics Explorer mission (M & R p. 280).

Ultra-violet and Optical Astronomy Group

Boksenberg's involvement in ultra-violet astronomy, with the instrumentation of the UV scan experiment on TD-1 and as project scientist for the UK side of the IUE programme, has already been referred to on pp. 96-97. In 1969 he collaborated with Wilson in writing a comprehensive review of ultra-violet astronomy (Ann. Rev. Astron. Astrophys. 7, pp. 421-472, 1969). On 16 June 1973 they collaborated with the Culham Laboratory in a successful launching from Woomera of a Skylark rocket for high resolution UV spectroscopy of the bright stars, g² Velorum and z Puppis (see pp.106-107). Meanwhile Boksenberg had established his own group which, with substantial SRC funding, proceeded to work on three main fronts: satellite UV astronomy; balloon UV astronomy; and optical astronomy.

Satellite UV astronomy

The group participated in the scientific analysis and interpretation of data from TD-1 which was launched from Western Test Range, California at 1.55 hr GMT on 12 March 1972, the orbit being circular, sun synchronous, and nearly polar. Although the onboard tape recorders ceased functioning ten weeks after launch, some 60% of the data were soon being recovered in real time and by January 1973 this had been steadily increased to over 95%. Some 30,000 stars down to the ninth visual magnitude were scanned in two six-monthly sky scans. The sky surveys provided broadband ultra-violet spectra of many stars for the first time, making possible the determination of extinction as a function of wavelength in different directions within the galactic plane. One of the main achievements was the first analysis of the chemical composition of Wolf-Rayet stars.

The largest of the seven experiments on board TD-1, namely the UV scan experiment covering the wavelength range 1350-550 Å in 60 channels with a grating spectrophotometer, and a single photometric channel with peak response at 2740 Å and bandwidth near 300 Å became fully operational on orbit 107. The results obtaned during the first few weeks after launch covering stellar observations, interstellar extinction, Wolf-Rayert stars and the Large Magellanic Cloud soon appeared in Nature, Vol. 238, 34, 1972 and Mon. Not. R. Ast. Soc., Vol. 163, 291, 1973 (Boksenberg, Wilson & their colleagues from the UK and Belgium).

Boksenberg and J-C. Gerard of the University of Liege while carrying out their main function of observing stars, reported incidental observations of equatorial ultra-violet dayglow above 540 km. The main features of the dayglow were explicable on the basis of resonance scattering of sunlight by Mg⁺ ions.

He and D. Carnochan with J. Cahn and S. P. Wyatt of the Department of Astronomy, University of Illinois, obtained the far ultra-violet spectrum (1350-2550 Å) of the central star of the planetary nebula, NGC 6543. The adopted temperature and angular radius were (40,000 ± 4000) K and (2.5 ± 0.5) x 10^-11 rad. respectively. The temperature and range of likely luminosities of the central star placed it near the beginning of the Harman-Seaton evolutionary sequence, consistent with an enveloping planetary nebula that was young and optically thick.

The group's main research involvement in the IUE was the development of the television detector system, and the design of the sun baffle to allow the observation of stars 10¹⁵ times fainter than the sun. IUE was launched on 12 January 1978, the onboard instruments functioning well from the start.

Balloon UV astronomy

The group collaborated with the University of Belfast in a programme of spectral observations of stars and interstellar gas in the balloon ultra-violet. Spectral observations at a resolution of 0.1 Å covering the region 2730-2880 Å were made with an objective grating spectrograph mounted on the UCL balloon-borne, star-stabilised system. Of particular interest were the interstellar lines of Mg II at 2795.53 and 2802.70 Å and Mg I at 2852.13 Å, the two important astrophysical reasons being: (i) since Mg is predominantly in the Mg⁺ state in the general interstellar medium, the interstellar abundance of Mg can be determined directly from the measured widths of the Mg II doublet lines, thus avoiding the difficult problem of allowing for atoms in unobserved states by consideration of the ionization balance, which is encountered in the optical region for Na and Ca; (ii) observation of both Mg⁺ and Mg^o gives information on the ionization balance, and values for the interstellar electron density can be derived using estimates of the interstellar radiation density. 5.7 x 10⁵ m³ capacity balloons were launched from the National Centre for Atmospheric Research Balloon Flight Station, Palestine, Texas reaching a float altitude of c. 40 km at which the zenith atmospheric transmission is in the region of 50% for the range of wavelengths concerned.

During 4/5 October 1972 spectral observations were made of the interstellar lines of Mg II and Mg I in the directions of stars in Orion and Cassiopeia from which the interstellar Mg column density and interstellar electron density were derived.

For the two coolest stars studied (b Orion and a Lyra) wavelengths of all spectral features in the aforesaid range were obtained with an accuracy of c. ± 0.04 Å. From these results the velocity field in the atmosphere of b Orion was investigated and evidence found for an outward motion in the higher layers and a pulsation-type motion in the deepest layers. The strength of the Mg⁺ resonance and subordinate lines near 2800 A for all the stars observed was compared with non-l.t.e. calculations, good agreement between observation and theory being found for main sequence stars, but the stronger lines in the super giants implying microturbulent velocities greater than 10 km s^-1.

Spectral observations of interstellar Mg in the Mg II doublet lines at 2795.5 Å and 2802.7 Å and Mg I at 2852.1 Å in the directions of stars in Orion, Scorpius and Virgo enabled values for the interstellar Mg abundance and electron density to be derived for the gas in the directions observed. The results indicated that the predominant ionizing mechanism in cool clouds is photoionization by starlight.

During 19/20 1974 May the spectra of nine stars were obtained covering the region 2870-2740 Å with an accuracy better than 0.1 Å. The discussion of the analysis of the spectra was presented in three papers. In the first, concerning four, nearby, unreddened stars, namely a Leo, h UMa, s Sgr and a Vir, values were derived for the interstellar Mg abundance and electron density for the gas in those directions. In the second, concerning the more reddened stars, namely, b, d, t Sco and b Cep, it was found from the relative Mg/H abundances that Mg was depleted by a factor of approximately ten for the moderately reddened stars, b and d Sco, E(B-V) about 0.2, while for t Sco and b Cep, E(B-V) about 0.5, the Mg/H abundance was closer to the solar value in accord with earlier studies of Orion stars of similar reddening. A comparison of the results and those obtained for Orion with interstellar Na observations gave a constant Na/Mg abundance ratio indicating similar depletion factors for Na and Mg over the range of E(B-V) studied. There being no evidence in the spectrum of d Sco for the high velocity gas components reported by Hicks et al, the third paper considered several physical conditions in an attempt to explain the anomalously low Mg^o:Na^o ratio implied by the observations. It was concluded that if the features were not of a time-dependent nature, then Mg is underabundant with respect to Na by at least an order of magnitude in the high-velocity components in contrast with the previous general findings.

Members of the group associated with Boksenberg in this work were B. Kirkham, Elizabeth Michelson and M. Pettini; also involved were W. A. Towlson and T. E. Venis, who with H. S. Tomlinson, designed and developed the UCL balloon platforms for infrared and ultraviolet astronomy (see p.108).

Optical astronomy

A new type of detection system for optical astronomy, known as the UCL Image Photon Counting System (IPCS), was conceived by Boksenberg in 1968 and thereafter developed with SRC funding. In essence, a high gain image intensifier capable of registering single photons was optically coupled to a television camera, which was interfaced to an on-line computer. The system was capable of photon counting in at least 10⁵ image elements simultaneously, so behaving as a vast bank of photomultipliers operating in the counting mode. Because of the on-line processing, noise pulses were largely rejected, storage capacity was essentially unlimited and signal integration was linear. Another feature was the capability of time resolution in increments of a few milliseconds per frame. The President of the International Astronomical Union at the Conference on Auxiliary Instrumentation for Large Telescopes, held in Geneva in 1972, stated: "The photon event counting system of Boksenberg of University College London is the purest answer to the questions of recording information in astronomy". It was to become used on most of the world's largest telescopes, attracting the foremost astronomers to collaborate with Boksenberg in studying outstanding astronomical problems, including those related to cosmology.

Instances of its use with the 98-in Issac Newton telescope (INT) at the Royal Greenwich Observatory (RGO), Herstmonceux and with the 200-in Hale telescope (HT) on Mount Palomar in California in the first half of the seventies follow. During the observation of spectra of faint objects with the HT, at a resolution (0.7 Å) theretofore unprecedented, priority was given to the quasar, PKS 0237-23; an analysis of the 75 absorption lines obtained, combined with 26 from other sources, posed a number of intriguing questions, particularly the strange doublet behaviour of the redshifts, and the possibility that absorption line-locking played some role in determining the actual distribution of redshifts ( Boksenberg & W. L. W. Sargent of the Hale Observatories). A systematic spectrometric study of the brightest quasar, 3C 273, covering a range of dispersions between 30 and 210 A mm^-1, yielded improved spectra, particularly of the blue region, showing previously undetected features. Emission line widths were compared with photoionization models (Boksenberg & K. Shortridge with

R. A. E. Fosbury, M. V. Penston & A. Savage using the INT at the RGO). Spectral observations with the IPCS on the HT covering the wavelength region 3300-6500 Å of the object associated with the unusual variable radio source 2005 + 403 near the galactic plane showed it to be a QSO with an emission redshift of 1.736 (Boksenberg, S. A. Briggs & R. F. Carswell with M. Scmidt of the Hale Observatories & D. Walsh of the Nuffield Radio Astronomy Laboratories, Jodrell Bank); those covering the range from c. 3300 to over 7000 Å of the red stellar object associated with the highly asymmetric double radio source, 3C 68.1, showed it to be a QSO with red shift 1.238, the spectral index of the optical continuum being c. 6, a value considerably steeper than that previously found for QSOs (Boksenberg & Carswell with J. B. Oke of the Hale Observatories).

Spectral observations of Seyfert galaxies included new observations of the optical spectrum of NGC 4151 with the IPCS mounted at the camera focus of the Unit Spectrograph at RGO; two spectra with resolution 1 Å covering the spectral regions 3727 to 4363 Å and H g to 5007 Å spanned the blue region and one spectrum covered the red region from H b to c. 8000Å with 5 Å resolution; and scans covering the wavelength region from 3240 to 11240 Å were obtained using the MultiChannel Spectro-Photometer (MCSP) at the Cassegrain focus of the HT. The underlying broad line spectrum in NGC 4151 was similar in nearly all respects to that of 3C 273, and the similarity of the ratio of broad-to-narrow line intensities of H beta and He I (5876 Å) suggested that the low-density gas in the galaxy was excited by radiation with much the same spectrum as that exciting the high-density region nearer the nucleus. (Boksenberg & Shortridge with Messrs. D. A. Allen, Fosbury, Penston, & Savage of RGO). Further ultra-violet spectral observations of NGC 4151 with the INT at the RGO were obtained by Boksenberg and Penston, namely at 1.3 Å resolution from the short-wavelength atmospheric cut-off to 4000 Å, since studies by previous workers had been most detailed at wavelengths longward of the O II lines at 3727 Å. The identifications, equivalent widths and intensities of emission lines in the wavelength range 3130 to 3966 Å were given. Observations of the spectrum of the nucleus of NGC 3516 yielded accurate measurements of emission-line intensities and profiles (INT); an explanation of the emitted spectrum with the aid of a photoionization model; and a correlation of the emission-line variability with physical conditions in the nucleus (Boksenberg & H. Netzer of the Department of Physics and Astronomy, Tel-Aviv University and the Wise Observatory). Spectra, scans and a direct electronograph were obtained of Markarian 231, using respectively the INT at Herstmonceux, the MCSP on the HT on Mount Palomar, and the RGO electronograph camera on the 40-in telescope at the Wise Observatory, Israel; these gave rise to two interpretations of the continuum, each placing the galaxy among the quasars in optical luminosity; a synthesis of the observed emission spectrum; the structures of three absorption line redshifts; and two possible configurations for the nuclear components of the galaxy (Boksenberg & Carswell with Messrs. Allen, Fosbury, Penston & Sargent).

Spectra of three Wolf-Rayet stars in M33 covering the wavelength range 3450-5150 Å were obtained with the HT; one object, WR-13, was found to be a WN star, probably WN5 or WN6; the second, WR-16, was confirmed to be a WC star, although, contrary to previous contention, its spectrum in the aforesaid range was consistent with a Galactic WR classification of WC7; and a third object, previously unclassified, in the H II IC 132 was found to be a WN4 star. (Boksenberg & A. J. Willis with L. Searle of the Hale Observatories).

Spectra of the nucleus and plates of the galaxy NGC 5506, suggested as the X-ray source, 3U 1410 - 03, were obtained with the INT and the Anglo-Australian telescope. Photographs showing it to be a highly elongated system, crossed by dust lanes and possessing a prominent nucleus, supported its classification as an irregular Type II, morphologically superficially resembling M 82. The nuclear spectrum implied that the object was active, greatly enhancing the probability of association with the X-ray source (A. S. Wilson of the Astronomy Centre, University of Sussex with Messrs. Boksenberg, Fosbury, & Penston).

A study of the rotation and gravitational redshift in some dozen hydrogen-atmosphere DA white dwarfs with the Palomar coude image tube and the IPCS implied that degenerate stars have low specific angular momentum and since, they have lost most of their mass, transport of angular momentum across molecular-weight barriers must be an efficient process (J. L. Greenstein of the Hale Observatories with Boksenberg, Carswell and Shortridge).

Boksenberg became a Fellow of the Royal Society in 1978, the same year that he was appointed Professor. In 1981 he was appointed Director of the RGO, but retained a position as Visiting Professor at UCL.

The Observatory Group

After becoming Perren Professor in 1972, Wilson continued with research carried out in his previous position as Director of the SRC Astrophysics Research Unit, Culham, namely the means of heating the solar corona and some studies of plasma spectroscopy. He began studies of the current data arriving from the sky-survey telescope on TD-1, and he continued to be involved in the IUE project on the UK management side, firstly as a consultant in 1973, and then as director, nominally on a half-time basis, from May 1975.

Ultra-violet observations of g² Velorum (WC8 + OPI) were made by the sky-survey telescope on TD-1 in 1972 and 1973 at different phases in the period and analysed by Wilson and Willis. The luminosity ratio of the two components showed that the O9I star was the brighter in the UV, as well as the visible, by between 1.4 and 1.8 mag. The spectrum of the WC8 component agreed well with the UV spectrum observed for a single WC8 star, HD 192 103. Considerable variations in the spectra of g² Velorum were interpreted in terms of an eclipse of the O9I component by the stellar wind resulting from the expanding WC8 envelope. An estimate was made of the mass loss from the WC8 component, but its accuracy was severely limited by the uncertainty of the carbon abundance in the WR component.

Wilson & Boksenberg had collaborated with the Culham Laboratory in the second successful launching from Woomera on 16 June 1973 of a star-pointing Skylark rocket. The vehicle was equipped with a three-axis attitude stabilisation system and instrumentation for high resolution UV spectroscopy of g² Velorum and z Puppis. The objective of the flight was to record the spectra with adequate spectral resolution to observe interstellar absorption lines and to study line profiles produced in the stellar atmosphere and the expanding circumstellar region. The instrumentation included three objective grating spectrographs giving three overlapping ranges to cover the wavelength band from 900 to 2300 Å. The linear dispersion was 0.12 mm/Å with a theoretical optimum spectral resolution of c. 0.3 Å. The first star was observed for 103 s and then a programmed change of vehicle attitude was made to acquire the second star, which was observed for 62 s, the period being terminated by loss of stabilisation when the altitude of the payload decreased below 120 km. The high-quality spectra obtained of both stars gave new information about their stellar atmospheres and the interstellar gas in the direction of the Gum Nebula.

Wilson and Willis studied the most extensive set of observations then available of the UV spectra of Wolf-Rayet stars; they were made by the sky-survey telescope on TD-1 and covered nine objects - three WC, three WN and three WC + O binaries. The observations, combined with ground-based observations, were analysed for both the continuum energy distributions and line strengths. The flux distributions, corrected for interstellar extinction, were compared with model atmosphere calculations to give colour temperatures, and Zanstra temperatures were computed from the intensity of the He II 1640 Å line resulting in some 30,000 K, somewhat lower than previously thought. The strengths of He, C and N lines in four WR stars (one WC and three WN) were analysed theoretically to obtain the abundances of these species, it being known that the H/He ratio was negligible in WR stars. In the WC star the C/He and N/He ratios lay close to the normal cosmic value whereas for the WN stars the N/He ratio was slightly higher, and the C/He ratio much lower than normal. Thus it appeared that the C abundance was the controlling factor in determing the spectral characteristics of the WN and WC sequences, and it was concluded that WR stars were in the helium-burning phase, the WN stars being less evolved than the WC.

Wilson with K. Nandy & G. I. Thompson of the Royal Observatory, Edinburgh, and C. Jamar & A. Monfils of the University of Liege, Institute of Astrophysics undertook a systematic study of UV interstellar extinction with the sky-survey telescope. Firstly c. 100 reddened stars located in the three directions of Cygnus, the galactic centre and the anticentre were studied to derive mean extinction curves, remarkably similar with a strong maximum at 2200 Å. The curves were derived from a comparison of reddened and unreddened stars of the same spectral type, although the accuracy was limited by the relatively restricted number of sufficiently unreddened stars suitable for comparison. This number was therefore increased in a second study of several hundred stars by the inclusion of slightly reddened stars to obtain a sufficient sample in each spectral type and luminosity class. The stars were divided into groups according to their galactic positions and a mean extinction curve derived for each galactic region situated in the local arm, the Carina-Sagittarius arm and the Persus arm. The curves did not show any significant differences so all the observations including UVB data were used to give a single mean curve in terms of total extinction for unit visual colour excess. The apparent constancy of the interstellar extinction law was confirmed by the same mean value per unit visual colour excess in each galactic region. However in the case of the colour excess E(2190-2500), which is linearly related to the 2200 Å feature, a few individual stars appeared to show anomalous behaviour.

Wilson & D. J. Carnochan with Nandy & Thompson studied the galactic distribution of the agents causing the extinction bump near 2200 Å and the UV colour excess E(1550-2740) within 2 kpc of the Sun in the galactic plane. The mean reddening - distance relation in the galactic plane was obtained for different longitudes. A study of the extinction parameter with galactic latitude showed a strong concentration of the dust towards the galactic plane with a scale height of 110 pc.

Using the sky-survey data, Willis and Wilson showed that the UV extinctions of the WR stars, WN6 HD 192163 and WC7 HD 156385, exhibited a pronounced excess in the 2200 Å absorption band. Although the former was surrounded by the nebulosity NGC 6888, no nebulosity associated with the latter was detected. Because of their similarity to WR stars, in sharing the characteristics of extended atmospheres and mass loss, the UV data for 23 Of stars were analysed, but no extinction anomalies were found.
The launch of IUE on 12 January 1978 opened up the study of astronomical objects from normal stars to quasars and clusters of galaxies enabling Wilson and his colleagues to gain an international reputation as one of the leading centres of cosmic ultra-violet astronomy. Wilson was elected FRS in 1975; awarded the CBE in 1978; succeeded Heymann as Head of Department in 1987; received the USA 1988 Presidential Award for Design Excellence on behalf of the British scientists involved in IUE; and was created a Knight Bachelor in 1989.

D. McNally having developed a spherically symmetric model of star formation, had relaxed that constraint in order to include the effects of rotation and magnetic fields. The problems were severe, but two methods of solving the equations appeared promising. Approximate studies suggested that previous ideas about the inhibition of star formation by rotation could be wrong, and questioned the entire problem of stellar instability produced by rotation. His study of the interstellar medium from which stars are formed also involved W. B. Somerville. It was based on the analysis of interstellar absorption lines in the spectra of distant stars observed with large telescopes, mainly the 74 inch Radcliffe telescope in S. Africa, and the 100 inch telescope at Mt. Wilson. The work benefited from observations in the ultra-violet and infra-red spectral regions by other groups in the department, and would be extended by use or the IUE.

W. B. Somerville was also developing theoretical models of stellar atmospheres for the analysis of observed stellar spectra to determine the temperature, density and chemistry of the atmosphere. In addition quantum mechanical calculations of atomic structure were being made (see p.132).

D. R. Fawell was analysing observed spectra on the basis of model atmospheres to determine the chemical composition of metallic-deficient and metallic-excess stars, the former being very old stars, whose composition is representative of a very early stage of the galaxy, and the latter having an anomalous chemistry not fully understood. Ultra-violet spectra from TD 1 were adding to those in the visible region.

J. E. Guest was involved in a geological study of the Moon and planets using pictures received from the American space programme in which he was accorded scientific investigator status. The Apollo mission led to studies of lunar volcanism and the mechanism of impact cratering. The flybys of Mercury by Mariner 10 on 29 March and 21 September 1974 led to a series of joint papers on the geologic/terrain map; tectonism and volcanism; and some comparisons of impact craters on Mercury and the Moon. The Viking project launching two unmanned spacecraft to Mars in 1975 led to another series on some Martian volcanic features; Martian impact craters and emplacement of ejecta by surface flow; geology of Chryse planitia; geological observations in the Cydonia region; geology of the Valles Marineris; and geologic map of the Casius quadrangle of Mars. The work indicating the importance of volcanism as a planetary process led to the study of the eruptive mechanisms on the volcano Etna as a complementary programme.

Infra-red Astronomy Group

As mentioned on p. 63, this group was started by Massey in 1966 to make observations in the far infra-red spectral region, the one in which very few astronomical observations were being made, by using a telescopic system carried on a plastic-film balloon to altitudes where the atmospheric absorption, particularly of water vapour, was negligible. Jennings, whose work on the microtrons had ended, became leader of the group, being joined by his associate, Aitken, who was to concentrate on ground-based observations, and Dr. T. A. Clark, a newcomer to the department, who had some experience in the use of high altitude balloons.

In 1965 interest in the use of balloon platforms for scientific observations had led to a National Balloon Programme to facilitate the work of the universities in this field. Having completed their work on the liquid bubble chamber, Tomlinson, Towlson and Venis of the Engineering Design Group, were free to undertake a design study for a balloon-borne stabilised platform for general use on which scientific equipment could be mounted. A tour of USA studying balloon payloads built there, convinced Tomlinson that no single platform could meet the diverse requirements of all balloon experiments. Hence the design study concentrated on stabilising a telescope to point accurately at selected stars. The proposed design did not materialise owing to financial restraints, but the experience gained was put to good use when in 1967 Tomlinson put forward a a design for a balloon-borne telescope system, tailored to the requirements of the infra-red group, which was able to be built in the departmental workshop. The platform of dimensions 1.7m x 1m and 2.3m height and loaded weight 340 kg carried a 40 cm, f/5.5, Cassegrain, Dall Kirkham, telescope, biaxially pointed and stabilised to ±1 min arc by a star sensor with a 2 deg field of view and + 5 guide star magnitude requirement. Acquisition of a selected star was programmed or commanded by reference to a magnetometer and the elevation angle, and for scanning the telescope was offset sequentially from the star tracker to cover an area of ± 5 deg arc from the guide star. A plane, Nasmyth, mirror reflected the beam through a hollow elevation shaft, where a gold-plated mirror reflected the infra-red radiation into the photometer while transmitting visible radiation to a photomultiplier tube. The photometer used a gallium-doped germanium bolometer, together with a quartz Fabry lens, filters, and an aperture stop, all cooled to 1.8 K in a liquid helium cryostat. The telescope, when built, was taken to Australia, where with the help of Professor Hopper's group at the RAAF Academy, Point Cook, Victoria, it was assembled and taken to Mildura for its first flight in July 1970. A second platform was constructed in the department for Boksenberg's ultra-violet astronomy studies.

Meanwhile, in order to test the suitability of observing sites, the group developed a simple, portable instrument for making observations of the water vapour content of the earth's atmosphere from the ground by comparing the intensity of solar radiation in and on the edge of water vapour bands at 0.94 or 1.87 m, both spectral bands in the operating region of lead sulphide detectors being selected by interference filters. Messrs. R. A. Hirst and J. Todd, visitors from the University of Melbourne, Australia were associated with Jennings in this work. A Michelson interferometer, of the type developed by Dr. H. A. Gebbie of NPL, was built and used by Jennings and A. F. M. Moorward with Fourier transform multiplex techniques and a vacuum thermocouple detector in a flight made from the National Centre for Atmospheric Research (NCAR) Balloon Flight Station, Palestine, Texas on 19 August 1969 to measure the thermal radiation from the atmosphere in the range 100-1000 cm^-1 (10-100 m), with a mean resolution of 34 cm^-1, as a function of height up to 38 km. The results showed that considerable emission was still present at aircraft altitudes and that radiation from the 15 m CO₂ band was still received at 38 km. Only at altitudes above 30 km could the transmission in the 100-300 cm^-1 (33-100 m) region be considered complete. Then in the following September measurements were made of the brightness temperature of the Sun in the range 65 to 180 cm^-1 by Clark, Jennings and G. R. Courts during a balloon flight to a height of 32.6 km from NCAR using the Michelson interferometer with a Golay cell detector. A platform built for the SRC by the Hi-Altitude Instrument Co. Inc., Denver was used in this work.

Observations were made with the UCL telescope, using the 40-350 m waveband, the short wavelength 'cut-on' being determined by the quartz Fabry lens and a black polythene filter and the upper limit by diffraction effects. The system's relative response, having been determined by laboratory measurements in a vacuum tank using a Michelson interferometer, was made absolute by observing a suitable planet during flight. Progress was rapid, the group establishing a leading position in the field. At the Eighth ESLAB Symposium, held during 4-7 June 1974 in Frascati, Italy, on H II regions and the Galactic Centre, 40-350 m fluxes were presented for 56 sources, observed within the telescope's pointing accuracy to be coincident with thermal galactic radio sources of known G numbers. The infra-red and radio continuum data were used to investigate the relationship between infra-red and radio flux, and to estimate effective dust absorption depths and dust-to-gas ratios within the ionised regions.

Two flights of the UCL balloon-borne telescope took place from NCAR in September, 1971, the performance being satisfactory. Broad-band, 40-350 m, flux measurements were made for the far infra-red sources in the Orion Nebula (M42) and NGC 2024, and an upper limit was established for the far infra-red flux from the Crab Nebula (M1). These observations were made on the second flight, when Saturn was observed to determine the flux sensitivity of the system. Mars was observed for calibration purposes on the first flight, when four sources, not previously observed in the far infra-red, were detected. Of these, one appeared coincident with the continuum radio source, G133.7 + 1.2, in W3, classed as a compact H II region, another was identified with a dark nebula, Lynds 1962, but no identifications with known objects were found for the others.

There followed a series of flights from NCAR during September 1972 and April to May 1973 bringing the total of galactic sources observed up to 56. In the former series, based on observations of Jupiter for absolute calibration, large 40-350 m fluxes were measured from a variety of H II regions, the far-infrared luminosities being mostly in the range 1 - 20 x 10⁵L_‰. Each source was observed several times, and contour maps of the two extended regions, NGC 6357 and NGC 6334, were constructed from a series of close scans. The sources DR 15, G351.6 + 0.2, RCW 117 and IC 4628 had not been observed before in the infra-red, and G334.4 - 0.4, together with the three components in NGC 6334 were new identifications. Three objects, namely KE 52, RCW 122 and RCW 117, lying on the edge of the Sagittarius arm, in a region where considerable star formation was taking place, were found to have luminosities greater than 10⁶ L_‰, and surprisingly high luminosities were found for DR 15 and G351.6 + 0.2. A scan of the reported position of HFE 28 failed to reveal any object of the required intensity to support its correspondence to G353 - 0.4, a compact H II region, associated with a class I OH source. The discovery of IC 4628, based on only one scan, required confirmation. The infra-red maps of NGC 6357 and NGC 6334 showed similar structure to that observed at radio-continuum frequencies. In the former case the two infra-red components corresponded to the two compact H II regions, the brighter infra-red component being associated with the weaker of the two radio sources.

However, in the case of NGC 6334 the brightest infra-red source did not coincide with a compact H II region, but was associated with an OH/H₂O maser source.

During the Spring 1973 flights, there were obtained a map of the W3 region and broad-band fluxes of RCW 36, RCW 38, W 49 and 24 objects mostly in H II regions lying along the galactic plane between longitudes 327 deg and 349 deg, the named objects being specifically searched for, and the rest identified later from raster scans in complex regions such as Norma. Three distinct 40-350 m emission regions were observed in W3, agreeing in position, to within 1', with the centres of the radio components on a 2 cm map, but the main continuum component, coinciding with the optically visible nebula IC 1795, showed a new feature, namely a pronounced extension. W3(OH), a weaker continuum source, but the strongest centre of OH emission in the region and containing an H2O maser, had a far infra-red flux 3.3 times greater than the 2 cm flux for W3 (continuum). The third source, W3(N), not previously measured in the infra-red, had a ratio of far infra-red to 2 cm flux only about half that of W3 (continuum). Three sources were detected in the region containing the optically identified and extended nebulosities, RCW 38 and RCW 36. W49 having a far infra-red luminosity of 22.5 x 10⁶ L_‰, appeared to be the most luminous far infra-red source outside the galactic central region. Seventeen sources all lying along 11 deg of the galactic plane in the direction of the constellation Norma and six along the galactic plane in the direction of the Scorpius constellation were observed. The Norma group included one source, identified with the optical nebula, RCW 99; two corresponding to thermal peaks associated with the optically identified nebula, RCW 106; and G333.6-0.2, one of the brightest radio sources, whose radio flux and far infra-red luminosity, of 2 x 10⁶ L_‰, implied the presence of of more than one early-type star in the region. The 8-13 m spectrum, measured by Aitken and Jones, clearly showed the 12.8 m line of Ne II, but was otherwise featureless; they considered the emission to arise from optically thin dust containing silicates, with extinction in a cold dust envelope cancelling the silicate emission feature (see p. 112). The Scorpius group included RCW 120 and two sources apparently associated with the single radio peak, G347 - 0.2.

Maps were also obtained of W51, a highly obscured region consisting of a number of compact H II sources, and also of the Galactic Centre region in the 40-350 m band. A low resolution spectrum (32 cm^-1 apodised) was obtained of the main component of W51, namely G 49.5 - 0.4, using a Michelson interferometer, following one of Saturn. Two raster scans of the W51 region were made, the first having 15 individual scans and the second 18, the scanning direction being approximately along the the line of the sources. Comparison of the final map with a radio map at 15 GHz showed that in general there was very close agreement between the infra-red and radio contours. The radio and infra-red positions of the four main components agreed to within 2', except in the case of G 48.9-0.3, which was unresolved from the small radio source, G 49.0-0.3, on the infra-red map. The peak infra-red fluxes of the four components G 49.5 - 0.4, G 49.4 - 0.3, G 49.2 - 0.4 and G 48.9 - 0.3 were 60, 19.5, 12.5 and 14.0 x 10^-10 W/m² respectively.

G 49.5 - 0.4, was known to consist of at least eight separate radio sources, the four strongest lying within a circle of radius c. 1¹/₂' and accounting for over 85% of the radio flux. The infra-red spectrum was based on a simple spherical model of the complex source, various measurements up to 1000 cm^-1 being used, including the series between 100 and 250 cm^-1 obtained by the Michelson interferometer during the flights. The agreement of the latter with a 100 K curve normalised from the photometric measurements was reasonably good, but the points did not lie on a smooth curve. It was found that for a grain temperature of 48 K both water ice and silicates gave reasonable fits to the data, with water ice showing fluctuations between 100 and 200 cm^-1 similar to those observed, but somewhat displaced, possibly due to impurities.

50 individual scans were made of the Galactic Centre region, the resultant map showing reproduction in the far infra-red of many of the radio features of a 5 GHz map. As well as the main components, Sgr A, Sgr B₂, Sgr C and Sgr D, there was a marked similarity between the contours to the north of Sgr A and the two radio sources to the south of Sgr C. The six sources of infra-red emission observed by Messrs. Hoffmann, Frederick & Emery (HFE) in their 100 m survey were confirmed except for the most southerly source, Sgr E in their paper, which was not seen. Separated fluxes, sizes and integrated luminosities were obtained for the main components, Sgr A, Sgr B2 and Sgr C, the separated luminosities of 36.5, 13.0 and 12.0 x 10⁶ L_‰ respectively, being approximately half the values reported by HFE for a smaller spectral band, 75-125 m. This was not necessarily inconsistent since the fluxes had been separated from the 'intensity ridge' which runs from Sgr B2 to Sgr C and were considerably smaller than the HFE ones.

Members of the group involved with Jennings in the foregoing observations and analysis of the data were Messrs. J. A. Alvarez, J. P. Emerson, I. Furniss, K. J. King and A. F. M. Moorwood; W. A. Towlson, with R. W. Catch, R. Want and A. H. Watts, prepared the system for flights and provided valuable assistance during the flights.

The construction at UCL of a Mk II balloon telescope having a larger aperture, 60 cm, and better stabilization, some 4" r.m.s., than its predecessor, led to a programme of astronomical spectroscopy at 0.05 cm^-1 resolution between 100 and 250 cm^-1, using a Michelson interferometer, designed primarily for measurements of fine structure emission lines from H II regions. The first flight of the system took place at NCAR in October 1976, when only atmospheric results were obtained owing to an early power failure on the telescope system, and unfortunately a free-fall destroyed the gondola. After rebuilding the system was launched on a successful series of flights, starting in the Spring of 1978, when observations were made of O III, O I, and N III fine-structure lines in H II regions, this being the first time that both [O III] lines had been measured simultaneously. Observations continued to concentrate on the measurement of far infra-red fine structure lines in different regions, including the Orion Nebula and M17. They gradually came to an end as interest turned to satellite observations, in particular, on the Infra-red Astronomical Satellite, a joint effort effort by the USA, Holland and the UK, which operated continuously from January to November 1983.

As mentioned earlier, the group soon became involved in the use of ground-based instruments for observations through the so-called atmospheric windows where the attenuation is relatively small, Aitken taking a leading part in this side of the work. Working at the Mill Hill Observatory with the 24-inch reflector, firstly a Golay cell was used with a preliminary chopping and phase sensitive detection system. Then a more refined chopping system was developed for use with a gallium-doped germanium bolometer, cooled to 1.8 K by liquid helium. This was used with P. G. Polden to measure the 10 m flux from the Crab Nebula on four nights in January and February, 1971, the effective diameter of the telescope being reduced to 18 inch to optimize performance of the bolometer. The results of the observations indicated a flux of 170 ± 50 f.u. at 10 m, greatly in excess of 30 f.u., the expected value from the usual synchrotron model, the most likely explanation of the excess being thermal emission from graphite grains.

Instead of using variable interference filters for spectral observations, Aitken substituted a diffraction grating to attain higher and more consistent resolution. With Barbara Jones the 8 to 13 m spectrum of Jupiter was observed with resolution (fractional increment of wavelength) of 0.007 on two successive nights in May 1972 using the 60-inch Tenerife infra-red telescope, probably the first observations made with the telescope since it had become operational only a few weeks earlier. The spectrophotometer consisted of a grating mounted in a modified Czerny-Turner configuration and driven by a stepping motor, the radiation being detected by a gallium-doped germanium bolometer at 1.8 K. Resolution was defined by an aperture in front of a KBr Fabry lens forming an image on the bolometer. The aperture, lens and filters defining the 10 m region were in thermal contact with the base of the cryostat at 1.8 K.

The grating spectrometer and germanium bolometer were used by Aitken and Jones on the 98-inch Issac Newton Telescope at Herstmonceux in November 1972 to make observations of NGC 7027 from 10 - 12 m with resolution 0.005 and a beam size large enough to include the greater part of the H II region; they were undertaken to obtain further data on the S IV line at 10.5 m and the 11.3 m feature seen by Messrs. Gillet, Forrest & Merrill (GFM) when observing NGC 7027 between 8 and 13 m using a narrow band interference filter with resolution 0.015. The S IV line was clearly seen, as was the GFM feature, maybe resulting from thermal emission by MgCO₃ grains, and a previously unobserved sharp feature was detected at 11.9 m. A sulphur abundance between 6.86 and 7.12, relative to H = 12.00, was deduced from the intensity of the S IV line, and the possibility that the 11.3 and/or 11.9 m features were due to unresolved clusters of lines was considered. Further observations with the INT were made on 29 November 1972, namely medium-resolution spectra in the 8 to 13 m range of the infra-red source IRS 5 discovered earlier in the month by Messrs. Wynn-Williams, Becklin and Neugebauer during detailed mapping at 20 m of part of the compact H II region, W3. It appeared that IRS 5 was a luminous object suffering a large extinction by an extended dust cloud and that the cool source in W3, which had been observed at 100 m, was probably associated with this obscuring cloud. When compared with similar spectra of the Becklin-Neugebauer (BN) object in Orion and the galactic centre, IRS 5 appeared to be an extremely compact dust cloud, optically thick at 10 m and of high luminosity, probably containing a massive protostar. The 10 m emission from the galactic centre and the BN object could be thermal radiation from optically thin dust of the same composition as that obscuring all these scources. J. M. Penman joined Aitken and Jones in observations of ionized neon in the galactic centre, made with the grating spectrometer mounted on the 60-inch telescope at Izana, Tenerife, during May 1974 and then in September 1974, February and May 1975. In the first observations of the 12.8 m Ne II fine structure line from Sgr A (West) the thermal nature of the source was confirmed, the neon abundance in the region appearing approximately normal, and the gas to dust ratio very large. In the more extensive study, a search for Ne II line emission was made in a number of nearby regions. The line was found to peak at 12.81 ± 0.005 m, the source being established as a thermal H II region of low excitation with a near normal abundance of at least one heavy element. No northerly extension of the emission was found, as suggested by radio synthesis maps. Aitken, J. Griffiths and Jones investigated the effect of heavy element abundances in stellar atmospheres on the ionization structure of the galactic centre. They concluded that observations of ionized neon were most readily fitted on the basis of heavy elements being overabundant by a factor of three compared with solar values, and ionization provided by stars with effective temperatures around 40,000 K.

Spectral observations of G333.6 - 0.2, the compact and very bright radio and infra-red source, were made by Aitken and Jones with the Ratcliffe 74-inch telescope at Pretoria during two nights in July 1973, the wavelength range 8-13 m being explored in equal intervals of 0.021 m with resolution 0.005. The fine-structure Ne II line at 12.80 m was detected and a neon abundance in the range 7.63-7.93 found in agreement with estimates of the cosmic value. The continuum radiation was considered to be thermal emission from optically thin dust with extinction in a thicker cold dust envelope, both distributions containing silicates, and the optical depth of the dust in emission being consistent with the observed ratio of infra-red to Ly alpha excess. They were joined by Griffiths in the further observations of the source made in July 1975, the spectrometer/ photometer being mounted at the Cassegrain focus of the 150-inch Anglo-Australian telescope on Siding Spring Mountain. High resolution maps of the source were obtained in the Ne II line and infra-red continuum emission at 12.5 m, the remarkably similar distributions showing a simple, compact and nearly symmetric source. The spatial observations and the radio continuum properties of the source were explicable in terms of a simple distribution of density surrounding the ionizing source, the similarity between the neon line and infra-red continuum spatial distributions providing independent evidence for a region severely depleted of dust, especially in the compact core, compared with the interstellar medium.

Aitken and Jones mapped the nova-like, h Carinae at 12 and 20 m with a resolution limited by diffraction of the 74-inch Radcliffe during July 1972 and 1973. The results of this mapping, together with 10 m spectra of the inner and outer regions and a 20 m spectrum, showed a remarkable similarity to the visible spatial distribution and provided evidence for more complex infra-red structure, and indicated an optically thin inner region surrounded by cooler thicker dust. They were joined by Messrs. J. D. Bregman, D. F. Lester and D. M. Rank of the Lick Observatory, University of California, in making further observations of the nebula on the nights of 9-13 July 1976. The 4 m spectral observations were made with the Anglo-Australian telescope, the measurements being taken by the more sensitive, liquid helium-cooled, grating spectrometer with an array of 24 Hg:Ge detectors. The Brackett-alpha line of hydrogen and the adjacent continuum were observed at several positions along an E-W line through the centre of the nebula extending to the edge of the outer shell, the greater part of the line and continuum radiation arising in a small central source, slightly narrower in the line radiation. In the spatial and spectral studies of an ionization front region in the Orion nebula using the Mauna Kea Observatory 2.2 m and the Cabezon 1.5 m telescopes, the array of 24 Hg:Ge detectors were replaced by an array of 5 As:Si photoconductors, the central three, sampling adjacent spectral elements with a resolution of 0.045 m, and the outer two having a resolution of 0.015 m and separated in wavelength by 0.85 m. This type of photoconductor continued to be used with various telescopes including the 3.8 m UK Infra-red telescope in Hawaii, a notable instance being the use of between 3 and 30 photoconductors involved in the 8-13 m spectrophotometric study of 24 compact planetary nebulae and other emission line objects, resulting in 19 being published for the first time.

After becoming a Reader in the 1979-80 Session, Aitken left UCL at the end of the 1981-82 Session to join the Department of Physics at the University of Melbourne.

Positron Physics Group

This was another group started in 1968 at the suggestion of Massey. His interest in positrons stretched back to the theoretical prediction of their existence by the work of Dirac and Oppenheimer. In 1952 his old friend and collaborator in theoretical atomic physics, C. B. O. Mohr of Melbourne University, spent his sabbatical year in Massey's room and they made a preliminary survey of the collision processes of positrons and positronium in gases. With A. H. A. Moussa, a research student from Eygpt, Massey considered positronium formation in helium, and D. A. Fraser spending some time in the department, undertook calculations concerning positromium collisions in hydrogen and helium. Meanwhile Massey was anxious to develop an experimental research programme on positrons in gases. He persuaded Heymann and Duff, who were actively involved in experimental particle physics, to take on a new research student, J. J. Veit, to work on the quenching of positronium. Although some good measurements were made of quenching rates, the plan that new research students in high energy physics should gain experience with some positron experiments never materialised. However with the completion of the experimental research programme using the 50 MeV proton linac at Harwell to measure polarization parameters in double and triple scattering of nucleons by protons, Massey suggested to T. C. Griffith that he should switch to experimental work with slow positrons. The availability of radioactive positron sources enabling work to be carried out in the department being an added advantage, Griffith not only agreed, but persuaded Heyland, an electronics expert, who was in charge of the third-year undergraduate laboratory, to join them. Massey suggested that the aim should be directed towards obtaining information about cross-sections for positron excitation of molecular vibration and rotation by accurate measurement of decay time spectra for pure molecular gases and for mixtures with other gases - a future programme as it turned out. In 1970 L. O. Roellig spent a sabbatical year with the group and in the following year K. F. Canter, who had worked with Roellig on positron annihilation in helium at low temperatures, joined the group enabling it to make a good start.

The work of the group developed along two lines running in parallel, one leading to the determination of total cross-sections for positrons in gases and the other to the measurement of lifetime spectra of positrons in gases. In the former, the group pioneered the use of MgO powder to produce positrons of energy c. 1 eV and, in the latter, it increased the rate of accumulation of data by at least an order of magnitude in comparison with the standard method, and formulated an exact method of evaluating and removing the background due to random events leading to the derivation of the true lifetime spectra from the raw data. It soon became one of the leading groups in the field of experimental, low energy, positron physics

The development of positron beam technology advanced dramatically with the discovery and design of efficient moderators to produce low-energy positrons. A striking discovery was announced by Groce et al in 1969 when moderating positrons to low energies, namely, that the number of positrons per unit energy interval in a band of energies around 1 eV was several orders of magnitude greater than expected. Coleman, Griffith and Heyland using a sodium 22 source and a moderator involving the 'backscattering' of fast positrons from a gold-lined cylinder found a yield of one slow positron per one million fast positrons, a factor of ten better than that observed by Groce et al. Canter joined them in the use of the same apparatus when a further factor of ten improvement was achieved by allowing fine MgO powder to settle on the gold lining of the cylinder. Further improvement of moderator design was achieved by replacement of the cylinder with gold vanes coated with a layer of MgO powder, and then it was shown that the yield was not greatly reduced if the powder was deposited on a fine grid provided it did not block the holes between the wires.

Applying the time of flight method to deduce the positron energy, Coleman et al initiated the timing sequence by detection of each positron as it traversed a thin plastic scintillator at the start of the flight path and ended it with a single NaI well counter at the target end of the path. The positrons from the scintillator entered the flight tube through a thin Melinex window aluminised on the surface in contact with the scintillator. The flight tube had a straight section of length 70 cm, diameter 5 cm, followed by a 15 cm section, curved in an arc of 25 cm radius; it could be maintained at a vacuum pressure of c. 10^-6 Torr. An axial magnetic field confined the positrons to a helical path close to the axis all the way to the target. The last 2 cm of the tube was inserted into the well of the NaI counter and ended in an insulated Al foil target, biassed at a negative potential of 90 V to attract the positrons and ensure their annihilation in the target. The moderator used to produce the slow positrons was a short narrow copper cylinder, inlaid with gold foil, surrounding the axis of the flight tube at the radioactive source. The corresponding yield of low-energy positrons was one per million disintegrations of the Na 22 source or about 500 timed positrons per hour. The yield was substantially less for materials of lower Z than gold, e.g., copper, aluminium and polythene. A ten-fold increased yield was achieved when the gold surface was covered with a thin layer of fine MgO powder, obtained by holding the open end of the cylinder above burning magnesium, the energy of the positrons being 1.0 ± 0.5 eV. Further improvement in moderator design was achieved by replacing the tube with gold vanes, coated with a thin layer of MgO powder and inclined at 45 deg to the axis of the flight tube, a system similar to one stage of a venetian blind electron multiplier. The slow positrons from this moderator were produced almost in a plane normal to the axis and consequently suffered less time spread than those produced over the inner surface of the tube.

The time of flight of the positrons was measured by arranging for the light pulses from the detectors to be transformed into fast logic start and stop pulses, fed to a time-to-amplitude convertor, whose output was fed to a multichannel analyser where the time of flight was stored and displayed; it was also necessary to count the total number of of start and stop pulses accurately and, where necessary, allow for any loss of counts due to dead time effects. Fast counting electronics were essential, the high counting rates of c. 1.5 x 10⁶ counts/sec in the source counter presenting some special problems; this limited the source strength to c. 100 mCi. Slow positrons in the 1 eV peak were detected at a sufficiently high rate (c. 1-3/s) to enable the determination of accurate cross-section measurements.

Canter, Coleman, Griffith and Heyland made total cross-section measurements for positron-helium collisions in the energy range 2-20 eV using the gold-vanes moderator, the attenuation of the positrons being measured when high purity helium was continuously leaked into the flight tube. A preliminary value of the 8 eV cross-section for krypton was also obtained. Then they made the first measurements above 20 eV by extending the energy range to 400 eV in helium, neon, argon and krypton. The helium cross-sections were also determined by the static method in which alternate runs of duration 200 s were taken, firstly with the flight tube evacuated and then filled to the appropriate pressure; the results were the same as for the dynamic method. The attenuation was measured at several gas pressures and the cross-section was deduced from a logarithmic plot of the total number of positrons in the peak, which had a FWHM of 1 eV, as a function of gas density; no departure from exponentiality was observed in any of the measurements. Using the same apparatus and method over the same energy range as for the inert gases, Coleman, Griffith and Heyland investigated H₂, D₂, N₂, O₂, CO and CO₂.

With no forward scattering the time of flight spectra have the same shape for both vacuum and gas runs, the latter having reduced intensity. The cross-section may then be deduced from the ratio of the integral of the number of counts under the peaks for the two runs. With significant forward scattering the peak for the gas run is changed in shape, there being a tail on the low energy side of the peak, and the attenuation value at each channel in the peaks varies. Spectra for positrons in helium at 3, 30 and 300 eV showed that the ratio of counting rates per channel with and without gas was constant across the 3 and 30 eV peaks, implying no distortion, but it varied continuously across the 300 eV peak and only approached a constant value near channel 1 at the leading edge of the peak, where the contribution from scattered positrons tends to zero. The true attenuation, A, was therefore taken as the asymptotic value at the leading edge of the peak and the total cross-section was given by ln A /I, where I is the integral of the number density of gas atoms over the length of the flight path. This procedure was therefore introduced to make allowance for small angle scattering and for inelastic scattering involving small energy losses.

A plot of total cross-section against positron energy for all the inert gases illustrated a general pattern of increasing cross-section with energy, a relatively rapid rise occurring at the positronium threshold, to a maximum, the cross-section at a given energy increasing with atomic number. The rapid rise was most pronounced in the case of helium, the threshold being 17.8 eV and the maximum around 50 eV. In all cases the decrease of cross-section with decreasing energy at the lowest observable energy raised the possibility that a Ramsauer-Townsend minimum, such as occurs for electrons in argon, krypton and xenon, occurs at still lower energies. Theoretical analysis of the He results at energies below the positronium threshold, where only elastic scattering occurs, was carried out by J. W. Humberston and R. I. Campeanu. The variation of the elastic cross-section with positron wave number was in excellent agreement over the range corresponding to energies 2 to 20 eV.

The cross-sections in H₂ and D₂ were approximately the same at all energies, showing a rapid rise around 9 eV. Later results for hydrogen showed a distinct minimum between 2 and 4 eV followed by a gradual and then a rapid rise, starting at an energy near 8.63 eV, the positronium threshold; the rise in cross-section between 4 and 8.8 eV was assigned to elastic scattering, rotational and vibrational excitations since the break-up of H₂ is very small between the dissociation energy, 4.48 eV, and 8.8 eV. In the heavier gases the cross-sections were much larger than those for H₂ and D₂. In N₂, O₂ and CO there was a gradual increase from 2 eV to a maximum around 20 to 25 eV, followed by gradual decrease to higher energies. In CO₂ there was a sharp increase in cross-section close to the ionization threshold of 14.4 eV.

In the earlier experiments the correction for forward scattering did not fully compensate for the scattering which occurred near the target end of the flight path. A significant improvement in experimental technique was therefore made by the introduction of a gas cell into the flight path of the positrons to restrict the scattering close to the positron source. The cell of length 8 cm was mounted in a 20 cm diameter chamber inserted into the 90 cm flight path directly after the source assembly. Positrons entered and left the cell through small cylindrical apertures, from which the gas leaked out and was pumped away by a 4" diffusion pump beneath the scattering chamber. A 2" diffusion pump maintained constant conditions in the moderator region for vacuum and gas runs. A pressure differential of c. 50:1 between the cell and the main flight path resulted in some 80% of the scattering taking place in the localised region. Localisation of the scattering minimised the error due to failure of detection of small-angle-forward scattering and eliminated the spread of transit times arising from positrons scattered with uniform probability at all points on the flight path between moderator and detector. A series of time of flight spectra, obtained with this system for positrons in helium in the energy range 50 - 170 eV by Coleman, Griffith, Heyland & T. L. Killeen, exhibited the characteristic secondary peak corresponding to inelastically scattered positrons, not observed in the earlier experiments. A typical time of flight spectrum for 61 eV positrons in helium showed a secondary peak corresponding to positrons of energy 31 ± 1 eV, which had undergone inelastic scattering through small angles. Preliminary values for the total inelastic cross-section were deduced, namely 0.6 to 0.45 p a_o² for positrons with energies between 50 and 170 eV.

In an improved system, the scattering chamber had two stages of differential pumping arranged symmetrically on either side of the 8 cm gas cell, most of the gas therefrom being removed by a 4" diffusion pump mounted below, the remainder being removed by 2" diffusion pumps, one on either side of the cell; another 2" pump, 10 cm from the target end of the flight path, ensured that a minimum of target gas remained in that region under gas-flow conditions. Measurements of pressure at various points during gas-flow conditions indicated that c. 96% of the scattering occurred in the gas cell, the pressures in the moderator region and flight path being < 10^-5 Torr. Thus constant conditions were maintained in the moderator region both for vacuum and gas runs. Using a 150 mCi Na 22 source and a moderator consisting of two overlapping tungsten grids coated with fine MgO powder, Griffith, Heyland, K. S. Lines and T. R. Twomey remeasured the total cross-section for positrons of energy 20-1000 eV scattering in helium, neon and argon. In order to study inelastic positron-helium collisions in detail, vacuum and gas runs lasting over several hours were taken. The peak due to inelastic scattering was clearly separated from the unscattered peak at energies between 50 and 300 eV, but outside this energy range the separation was not so clearly defined. The same general features were exhibited by neon and argon, although the separation between the scattered and unscattered peaks was less since inelastic scattering forms a smaller fraction of the total cross-section. The total cross-sections for helium and neon agreed with recent results of Brenton et al, but those for argon were significantly lower; in all cases they were consistently higher than the results of Coleman et al. The helium and neon data agreed with the sum rule predictions of Bransden et al. Replacing the NaI well counter by a channel electron multiplier to detect the positrons, the same team investigated the inelastic scattering of positrons by helium at intermediate energies. A much higher signal to background ratio, namely 20:1, was obtained with the modified detector, up to 7 timed positrons per second being detected in favourable conditions. The measured time of flight spectra, based on runs of duration up to c. 200,000s were analysed and a partition of the cross-sections amongst the various inelastic channels at energies between 20 and 500 eV were attempted. M Charlton and G. L. Wright joined Griffith and Heyland in using the system to measure the total scattering cross-sections for positrons in the energy range 15-600 eV in H₂, O₂, N₂, CO₂ and CH₄. The modified measurement techniques and improved methods of correcting for forward scattering yielded results of higher absolute accuracy than the earlier measurements of Coleman et al. The new values of the cross-sections were higher than the earlier ones at all energies, confirming that the latter were not fully corrected for forward scattering.

The lifetime spectrum of positrons and positronium in a gas consists of the 'prompt' peak, due to the decay of para-positronium and positrons annihilating in the walls of the gas chamber and in the source; the shoulder region which persists while the positrons are slowing down due to collisions with gas atoms until they reach thermal equilibrium; and a composite region consisting of two overlapping exponential decay curves, one due to the thermalised positrons and the other to ortho-positronium. The decay constants for free positron and ortho-positronium annihilations are given by:

l_f = wrZ_eff ; l_p = _ol_p + 4 r ₁Z_eff

where r is the gas density in amagats; wr is the Dirac rate for a free electron gas; _ol_p the vacuum decay rate of ortho-positronium; and Z_eff and ₁Z_eff are measures of the corresponding effective numbers of annihilating electrons per atom. Another important parameter is the fraction F of positrons forming positronium and this is deduced from the amplitudes of the aforementioned decay curves. This can be compared with values based on the Ore model, namely that positronium will only be produced permanently by positrons with energies in the comparatively small range, the so-called Ore gap,

E_ex > E > E_i - E_ps

where E_ex is the threshold energy for excitation of the atom, which is not much less than its ionization energy, and E_ps is the binding energy, 6.8 eV, of the ground state of positronium.

At the start of their work on the lifetime of positrons and positronium in gases, Coleman, Griffith and Heyland used a thin plastic scintillator for direct detection of the positrons from the Na 22 source. This method of defining the 'start' pulse gave high counting rates with a weak source since some 30% of the positrons from the source entered the gas and were detected instead of the much less efficient detection of the prompt 1.28 MeV g rays in the standard method. The 'stop' pulse was defined by one of the g rays from annihilation of the associated positron, both g rays being detected in a fast plastic scintillator. The rate of accumulation of data was an order of magnitude greater than in previous work, more than 10⁷ events due to annihilation being recorded in a 24 hr period. Lifetime data were obtained with this system for argon, krypton and nitrogen. Coleman and Griffith also made a determination of the vacuum lifetime of ortho-positronium using Freon gas. However difficulties were experienced in ensuring a clean system owing to plastic therein, and the thin aluminium through which the positrons entered the vessel limited the gas density up to c. 15 amagats.

Coleman, Griffith, Heyland and Killeen developed a conventional lifetime system to exploit the exact signal restoration method for the data analysis. A small cylindrical pressure vessel, length 7 cm, diameter 3 cm, was machined from a drawn copper rod and had its inner surface electroplated with gold. A 5 mCi source of Na 22 was deposited on a gold spatula, mounted close to the wall of the vessel. The backscattering of positrons from the gold enhanced the proportion of positrons annihilating in the gas. The source was viewed by two 11.2 cm diameter x 7.5 cm fast plastic scintillators, mounted on photomultipliers. One scintillator was positioned behind the source to maximise the solid angle for detection of the prompt 1.28 MeV g ray, emitted within 3 x 10^-12 sec of each positron, which initiated the 'start' pulse of the timing sequence, the other being on the opposite side of the vessel to detect one of the 0.5 MeV annihilation g rays for the 'stop' pulse. 'Stop' pulses due to the 1.28 MeV g rays accounted for less than 20% of the background events; the rates for the 'start' and 'stop' pulses were c. 10⁴ and 2 x 10⁴ sec-1 corresponding to detection efficiencies of 6% and 12% respectively; the delayed coincidence rate was 10³ sec^-1; depending on gas density up to 65% of the events were due to positrons annihilating in the gas; and the overall time resolution was better than 1.4 ns FWHM.

Lifetime parameters were determined for the inert gases, He, Ne, Ar, Kr and Xe, over various density ranges. As an example of the measurements at 297 K, the following values are reproduced for He over the density range, 2-60 amagat: Z_eff = 3.94 ± 0.02; ₁Z_eff = 0.125 ± 0,002; the shoulder width = 1700 ± 50 ns amagat; and F = 0.23. Compared with theory the calculated value of 3.88 for Z_eff at room temperature agreed well with the measured value and the shoulder region was well reproduced by the calculated phase shifts. The results included the first measurement of the shoulder width for Ne, namely 1700 ± 200 ns amagat. The measurements of F were consistent with the extreme predictions of the Ore model, as were those for neon and argon but those for krypton and xenon were far too low. The positronium formation fractions taken in conjunction with the positron beam total cross-sections enabled estimates to be made for the values of positronium formation and positron excitation cross-sections for helium and, with reduced accuracy, for neon and argon in the energy range from the positronium threshold E_o to the ionization potential E_i. These cross-sections were found to be c. 0.2 pa_o² at E_i for helium and somewhat larger for neon and argon.

Measurements of the lifetime parameters for the molecular gases were also made for D₂, H₂, N₂, CO, CO₂, O₂ and CCl₂F₂. The shoulder region in N₂, the only molecular gas to exhibit this feature, was clearly established at 0.3 amagats. ₁Z_eff was found to be constant over a wide density range for N₂. CO, CO₂, H₂ and D₂, whereas for O₂ it was large and decreased from 80 at 7 amagats to 14 at 200 amagats. Zeff decreased with density for N₂, CO, H₂, D₂ and O₂ whereas for CO₂ it increased from 60 at low density to 120 at 50 amagats and for CCl₂F₂ from 750 to 1500 over the density range 0.3 to 5 amagats. F for N₂, CO, CO₂ and O₂ increased with density, a notable feature in N₂ being the increase from 0.19 near zero density to a maximum at 0.40 near 140 amagats followed by a gradual to 0.36 at 234 amagats.

All of the lifetime parameters are affected to some degree by the level of impurities in the gases under investigation, F and the shoulder widths being sensitive to small amounts of impurities. It was shown that as little as 50 ppm impurity in commercial grade helium increased F from 0.23 to 0.35, shortened the shoulder width by about 10%, but hardly affected Z_eff and ₁Z_eff . Measurements of F in krypton-helium gas mixtures gave a maximum value of 0.46 at a concentration of c. 0.1% of krypton in the mixture, this value exceeding the sum of the fractions for low densities for the pure components. Measurements were also made for argon-helium mixtures, the slope S_o of the graph of F against argon concentration at zero concentration determining the probability of positronium formation in positron-argon collisions and thus being a measure of the positronium formation cross-section for argon. Later Charlton, Griffith, Heyland and Lines derived the formulae for determining the cross-section from Ssub>o; determined the enhancements of F for small quantities of Ne, Ar, Kr, Xe, H₂, N₂, O₂, CO, CO₂, CCl₂F₂ and C₄H₁₀ in He; and obtained the corresponding cross-sections from the experimental values of S_o. Wright joined in the measurement of the energy dependence of the positronium formation cross-section for the gases He, Ar, H₂ and CH₄ by passing a beam of slow positrons through a scattering chamber and detecting the positronium formed by counting the triple coincidences from the 3g decay of ortho-positronium. This was the first direct determination of relative positronium formation cross-sections using the beam technique; it clearly revealed the energy dependence of the O-Ps formation cross-section and showed that positronium formation occurs mainly in the energy region between E_ps and E_i.

The decay rate of ortho-positronium was determined by Griffith, Heyland, Lines and Twomey as a function of gas density, the vacuum decay rate being deduced by extrapolation to zero density. Two conventional lifetime systems with sources of strengths, 1 and 2 mCi, respectively giving different signal-to-background ratios were used to check the signal restoration and analysis procedures. Two determinations were made with Freon-ammonia-helium mixtures, proportions c. 42, 42, 16%, respectively, two with iso-butane, one with n-butane and one with pure Freon-12 for comparison with the earlier data of Coleman and Griffith. The decay of the free positron component is so rapid for ammonia that the restored signal, after subtraction of the background, could be fitted to a single exponential term even for the lowest gas densities used. The most accurate results were obtained using iso-butane; n-butane had a smaller useful density range. The restored signal for Freon had to be fitted to the sum of two exponentials below 1 amagat with consequent loss of accuracy. The final value obtained for _ol_p was (7.045 ± 0.006)/ms, which agreed with the existing theoretical value.

The Group continued to flourish, Griffith being appointed Professor in the 1980-81 session; it continued to attract first-rate postgraduate students, one of whom, Michael Charlton, who had made the first measurements of the cross-section for positronium formation in gases, later succeeded Griffith as Head of the Group.

Image Processing Group

The leader of this Group, Dr. M. J. B. Duff, was a research student in the Department of Physics from 1953-56, working on the design of the fast recycling high pressure cloud chamber. After two years as a development engineer in the Infra-red Group at EMI Ltd., he returned to the Department as a Research Assistant to develop automatic devices for the measurement of tracks in nuclear emulsions, bubble and spark chamber photographs, and became a Lecturer in 1962. The group was originally known as the Automatic Methods Group, but by 1968 it had combined with the Data Machines Development & Maintenance Group to form the Technical Physics Group, which occupied the ground floor of the UCL Annexe in Flaxman Terrace. Facilities included electronic and mechanical workshops, dark rooms, a chemical and a clean laboratory, a drawing office, and offices for staff and research students. The technical services provided for the department and, to a limited extent for other departments in UCL and the University, included design and construction of special purpose circuits and equipment, provision of printed circuit boards and a wide range of thin film devices, produced by means of a 19" vapour coating and r.f. sputtering plant. Some development work, supported by the SRC, was also carried out on gallium doped germanium in an attempt to produce high sensitivity, low noise equivalent power, infra-red bolometers for the Infra-red Group.

Having developed his own research work into the general field of pattern recognition, or image processing, both from the theoretical and experimental point of view, Duff founded and then became the Organising Secretary of the national Pattern Recognition Group. Formed in 1967, it included representatives of nearly all the pattern recognition groups in England and met thrice yearly at UCL. Between 1971 and 1975 he received from the SRC grants totalling c. £70,000 for the investigation of parallel processing networks, a programme involving collaboration with scientists at the Laboratorio di Cibernetica, Naples, the University of Maryland, USA and the University of Sao Paulo, Brazil. A grant was also made for the development of an automatic method for optical recognition of vehicles during a traffic census. Further grants of c. £100,000 each were made in 1976 and 1978 respectively for the design and assessment of the fourth in the series of Cellular Logic Image Processors, namely CLIP4, and then the development of the system. CLIP4, the first largest working processor array constructed, was the winner of the British Computer Society Technical Award in 1985, the year when Duff was appointed the first Professor of Applied Physics in the department.

The first development by Duff was the Digiscat, a digitally controlled device providing a semi-automatic method for the measurement of multiple scattering of particle tracks in nuclear emulsions. The operations required for the measurement of multiple scattering by constant cell and constant sagittal methods were performed automatically each time an operator set a crosswire onto the track and pressed a footswitch. A printed list of y coordinates, their second differences and the sum of the modulii of the second differences were provided; a punched tape was also available. With J. Cox and L. J. Townsend an automatic following microscope was developed to search for, find, follow and read co-ordinates of black, grey and minimum tracks in nuclear emulsions with following speeds up to 10 mm. per min. Being particularly suitable to computer control, it was transferred to the Centre for Nuclear Research, Strasbourg for further development on-line to a computer. A digitised microscope for the measurement of bubble chamber track photographs was designed with C. J. Robinson, the coordinates points of tracks being recorded with an accuracy of ±21¹/₂ microns over a measuring area of 20 cm². Six microscopes were constructed, the last four being provided with a small plug-in unit at the back of the central control chassis to enable changes in the logic to be made for the analysis of spark chamber photographs. Then they devised a polar flying spot scanner to provide an intermediate speed measuring device for bubble chamber photographs. The scanner examined film in the neighbourhood of a vertex and, by means of a set of concentric circles, recorded the polar coordinates of sets of points at frequent intervals along each track radiating from the vertex. In all of the devices it was necessary at some stage to use human operators, e.g. to select photographs worthy of measurement or to guide the device to make measurements on relevant parts of the photograph. They lacked some form of built-in pattern recognition capability in the recording or scanning system. Hence by the mid sixties the Group commenced a study of pattern recognition, both from a fundamental point of view and also with the aim of constructing certain pattern recognition systems.

The research programme under the general heading 'Pattern Recognition Matrices' was originally divided into four parts: a preliminary study of existing techniques for the design and construction of logical networks with many elements; application of one of these techniques to the design of a network for vertex detection in bubble chamber photographs; construction of the vertex detection system; and a long term study of logical networks. Appreciating that human recognition of visual patterns is dependent on the operation of a highly elaborate parallel array of photodetectors, coupled through to many layers of parallel processing nervous circuitry, it was decided to restrict consideration to systems using multiple parallel inputs with highly interconnected logical arrays and using components which were intrinsically capable of microminiaturization. A library of Fortran subroutines was written, optimized and stored on a magnetic disk for use on the IBM 360/65 computer, the subroutines simulating many of the more important, parallel processing pattern recognition algorithms. The library was intended to test pattern recognition schemes in a range of practical applications. There followed a self-organising programme replacing the intuitive selection and application of algorithms by a systematic series of evaluations of the input data resulting in optimal selection of subroutines from the library.

B. M. Jones and L. J. Townsend collaborated with Duff in producing UCLPR1, the first parallel processing recognition system designed to find vertices in bubble chamber photographs. It was originally intended as a preliminary stage of processing to precede the polar scanner device. UCPR1 was a fixed logic, 400-processor system arranged as a 20 x 20 square array of photodetectors onto which were projected charged particle images. The outputs from the photodiodes, suitably thresholded, were first summed over three by three windows and then over a five by five ring of outputs from the first summation. Finally a global threshold was applied, reducing from a maximum until at least one output exceeded the current threshold level, when one or more miniature indicator lamps lit up in the corresponding positions in the output array indicating the approximate position of a vertex in the input image in about 20 ms. With a small circuit modification to ensure that detected points were elements of the input particle track image, the same system operating with an increasing threshold was able to locate line ends. By combining the two functions and by partitioning the output into regions, simple recognition of line figures, such as a subset of alphanumerics, was achieved. However it soon became clear that a simple four-layer processing array, comprising input, two summations and output, was only applicable to a few elementary tasks. Moreover the hand-assembled multilayer printed circuit boards were too restrictive. Consideration was given to the possibility of constructing an array with ten or more layers of logic, each performing a fixed function but allowing data to be moved in either direction between layers, but the technical difficulty of making the necessary connections between the layers was too formidable.

Discussions with Prof. S. Levialdi of the Laboratorio di Cibernetica, Naples, who had shown that simple array of switches, connected to detect closed loops in binary figures, was capable of passing information between processors over long distances in the array, led to a study of the intrinsic processing capability of an array of processing elements containing the smallest set of components consistent with the objective: input and output for image data, paths between adjacent processors, and means for inverting or switching on or off the outputs from the processors. A processing cell incorporated a two-pole, double throw toggle switch, a neon indicator with series resistance, and diodes linked to input and output buses surrounding each cell. A trial 5 x 5 cell array was constructed and at the same time a Fortran simulation was written and linked to a Monte Carlo programme exploring arbitrary connection schemes, chosen at random and applied to a standard test image. In a typical result, the programme taking about 30 minutes in the IBM 360 computer, c. 4000 trials generated c. 70 schemes each with different processing properties, and all 10 schemes which had been devised and wired into the actual array emerged from the Monte Carlo search after about 20 minutes. The diode array proved valuable for developing ideas about arrays of mesh-connected processors, but attempts to describe propagation algebraically were thwarted by the bidirectionalty of the diode paths for signals of opposite polarity. This led to the specification of a processing element in terms of pure logic functions rather than real circuit components.

The translation of the logic specification into the then newly available small scale integrated circuit led to the building of the first Cellular Logic Image processor, CLIP1. The processing element circuit consisted of eight two-input and two four-input NAND gates in three small scale integrated circuit packages. One hundred elements were mounted on a large printed circuit board to form a 10 x 10 array in which each element was connected to its nearest neighbours. A binary image, generated by a flying spot scanner, was stored in the input memory, a shift register. One of three possible functions was selected by appropriate control lines and the contents of the shift register connected to the array element inputs through 100 parallel output lines, the output data being buffered before re-entry to the shift register for display. The three functions chosen were extraction of the contents of closed loops of 1-elements, extraction of sets of 1-elements connected to the array border, and extraction of the outer edges of objects composed of 1-elements. Images were displayed by modulation of the brightness of a 10-line raster on the display oscilloscope. The input image was alterable pixel by pixel by means of a light pen interacting with the display of the input image stored in the shift register.

In CLIP2, a 16 x 12 hexagonally-connected array of processing elements, every element comprised two programmable Boolean processors each implementing independently the full set of functions of two inputs. The output of one processor was transmitted to its six neighbours, whilst that of the other went into an image memory for subsequent further processing or display. The two inputs were either both binary images or else a binary image at one input and the Ored interconnection signals at the other. Additional circuits allowed a second image to be Ored in with the the interconnection signals at the second input. As before, the input image was generated by means of a flying-spot scanner and light pen. Instructions were entered manually as 12-bit words and stored in a 32-word memory. As had been anticipated from the outset, the system was severely limited by the non-directionality of its operations. However its study, which was completed in 1972, led to the processor enhancement required to enable the array capable of performing any image operation.

This enhancement appeared in CLIP3, the interconnection structure between processors being improved by individually gating each direction, then 6 or 8 to provide hexagonal or square connectivity, and by replacing the OR gate by a threshold gate. The instruction word was increased to 24 bits and the instruction memory to 256 words; 16 bits of local image memory were provided at every processor, and various modes for loading data into this memory were allowed. Many programmes were written for CLIP3, ranging from conventional image processing to non-image operations such as maze solving, electrostatic field calculation, and lay planning - fitting together garment patterns for the economic use of cloth. By constructing a scanning system covering a 96 x 96 pixel image with the 16 x 12 processor array, the image area was increased sufficiently to enable programmes to be written to process grey-level images by the use of bit-serial algorithms.

In CLIP4 the processor specification was refined to produce a significant improved performance with the view to fabrication as a large scale integrated circuit so that larger arrays could be built at a reasonable cost. The performance of the scanned version of CLIP4, some 3000 times slower than CLIP3 itself, led to the 96 x 96 processor array, which overcame the loss of speed in the scanning operation. A chip including eight processors, each with 32 bits of local memory, was designed, the target price in 1974 being £6. However a full array of 96 x 96 CLIP4 circuits was not available until some 6_ years after placing the design contract. The CLIP4 system consisted of an array of 9216 bit-serial processors configurable as either a square or hexagonal array, interfaced to two framestores holding 6-bit images. The input store was loadable from a variety of television camera optical workstations via an A/D converter sampling the central part of a non-laced standard television frame; the output memory offloaded through a D/A converter for display on a standard television monitor, means being available for mixing, at variable intensities, the original analogue image and one or other of the input or output digital images. Communication with CLIP4 was via a DEC PDP-11 computer operating under UNIX. Although the serial host was time-shared, CLIP4 itself was only available to one user at a time, but control could be switched to another within seconds and the UNIX file system enabled users to keep track of the locations of both their programmes and their image data.

In the preface to 'Cellular Logic Image Processing', edited by Michael Duff and Terry Fountain, Duff traces the origins of the Image Processing Group from the Digiscat project in 1958 through the development of interest in all types of images to the extensive studies of computer architectures designed specifically for the analysis of two-dimensional data arrays, the emphasis in the CLIP programme being the building of systems primarily to study the relationships between architectures and algorithms. Various aspects of the CLIP system are described in representative extracts from the Ph.D. theses of some of the postgraduates using it in the five years after its commission, namely 'Basic Clip Processing' (S. D. Pass); 'Propagation in Cellular Arrays' (G. P. Otto); 'Software for CLIP4' (A. M. Wood & D. E. Reynolds); 'Serial Section Reconstruction' (H. H-S. Ip); 'Colony Counting and Analysis' (D. J. Potter); 'Computer Tomography' (K. A. Clarke); 'Motion Analysis' (A. M. Wood); and 'Automatic Segmentation' (D. E. Reynolds). In the final chapter Fountain, who directed the construction programme for the CLIP system, describes the CLIP7 project aimed at high-resolution (512 x 512 pixel) images processable at CLIP4 rates, and investigation of the concept of local autonomy within an array of processors, including alternative system architectures - particularly three-dimensional structures having novel connectivity nets.

Molecular Beam Group

This group started work in 1967 as a joint project with the Department of Chemistry, the main object being the investigation of some low energy atomic and molecular collision processes involved in chemical reactions. Its members were Profs. A Maccoll and D. J. Millen from Chemistry and Prof. Massey, Drs. S. J. B. Corrigan and J. Wilson, and research students G. D. Lempert and C. R. Howard from Physics. In order to study a range of reactions without the limitations imposed by the use of surface ionization detectors, a detector using electron impact ionization followed by mass analysis was used. The factors determining the signal to noise ratio of such a system were investigated by means of a commercial quadrupole residual gas analyser arranged as a molecular beam detector in an ultra-high vacuum system. The analyser was also used to explore a modulation system to improve discrimination against signals arising from ionization of the residual gas in the chamber. An apparatus was constructed in which two intersecting beams were formed by nozzles working under hydrodynamic flow conditions, it being known that such suitably designed nozzle sources gave very intense beams with velocity distributions much narrower than those from the Knudsen type of source; pumps capable of dealing with the large rates of gas flow were essential. From the fundamental point of view it was very important to make a detailed study of the reactive scattering of hydrogen atoms by the molecules H₂ and D₂ since it was only possible in such simple cases of comparing experiment with theory.

Investigations by Physics research students included a study of the velocity dependence of the total collision cross-sections of He-Ar, He-N₂, He-O₂, He-CH₄, He-CCl₄, Ne-Xe and Ne-Kr at thermal energies by observing the signal intensities due to the different velocity components of a molecular beam of one gas as it passed through a chamber at room temperature containing the other gas at different pressures (G. D. Lempert); the development of an arc-heated supersonic molecular beam source producing Ar beams with energies in the range 1.8-3.0 eV., Mach No. 5-6.5 and intensities of c. 2 x 10¹⁹ mol str^-1 sec^-1 observed and 2 eV H beams with Mach No. and intensities of c. 5 and 10²⁰ mol str^-1 sec^-1 predicted (L. S. Marvin); and a study of the dissociation of CO₂ by an electric swarm in a Townsend discharge and also by radiation of wavelength 1849 Å (P. Papacosta).

Atomic Physics & Astrophysics Group

The leader of this group, Michael John Seaton, on obtaining first-class honours in physics in 1948, declined an invitation to join Andrade's research team in favour of going over to the Mathematics Department to work under the supervision of David Bates. Between 1949 and 1951 during the work for his Ph.D. on quantal calculations of some reaction rates and their applications to astrophysical and geophysical problems he published six papers, three in the Monthly Notices of the Royal Astronomical Society and three in physics journals. On moving back to the Physics Department in October 1950 with Massey he continued with his research in atomic physics and astrophysics with great enthusiasm and skill to become one of the leading international authorities in the field, understanding the detailed methods for the calculation of atomic data and the requirements for these data in astrophysics. Seaton spent the 1954-5 session at the Institut d'Astrophysique in Paris, thus beginning a close association with H. van Regemorter and what was to become a close collaboration between UCL and the Observatoire de Paris at Meudon. Later this collaboration was extended to include the Observatoire de Nice. In 1961 he visited the University of Colorado at Boulder when the Joint Institute for Laboratory Astrophysics was being established, and in 1964 he was appointed a Fellow-Adjoint of the Institute in recognition of his contributions to its scientific activities; there followed an active collaboration with JILA in both atomic physics and astrophysics.

By the early seventies the group contained some twenty members including Drs. Gillian Peach and David Moores as lecturers, Hannelore Saraph as senior programmer, research fellows, visitors from other institutions and research students. Highlights included the development of some general computer programmes for the calculation of properties of highly ionized atoms, good results being achieved for the energy levels by making allowance for fairly complicated relativistic effects; calculations were also made on other properties such as radiative transition probabilities, and collisional excitation or ionization cross-sections. The development of generalized quantum defect theory and its application to problems in atomic structure and in electron-ion scattering, including radiative transition probabilities and dielectronic recombination led to a series of fourteen papers by Seaton and his collaborators over some twenty years. Work in astrophysics was mainly concerned with the properties of the solar corona, gaseous nebulae and the interstellar medium, quasistellar objects, and hot stars. Interest in the properties of the central stars of planetary nebulae led to a joint paper with R. J. Harman obtaining for the first time a well-defined track for these objects on the Hertzsprung-Russell diagram; they showed that these hot stars represented a natural stage in stellar evolution.

Some of the fields in which Seaton (and his group) have worked are described in articles by some of his colleagues and former students in 'Atoms in Astrophysics', published by the Plenum Press, to honour his sixtieth birthday on the 16th of January 1983. Edited by Messrs. P. G. Burke, W. B. Eissner, D. G. Hummer and I. C. Percival, these articles are on 'Low-Energy Electron Collisions with Complex Atoms and Ions', by P. G. Burke and W. Eissner; 'Numerical Methods for Asymmetric Solutions of Scattering Equations', by D. W. Norcross; 'Collisions between Charged Particles and Highly Excited Atoms', by I. C. Percival; 'Proton Impact Excitation of Positive Ions', by A. Dalgarno; 'Applications of Quantum Defect Theory', by D. L. Moores and Hannelore Saraph; 'Electron-Ion Processes in Hot Plasmas', by J. Dubau and H. van Regemorter; 'The University College Computer Package for the Calculation of Atomic Data - Aspects of Development and Application', by H. Nussbaumer and P. J. Storey; 'Planetary Nebulae', by D. R. Flower; and 'Forbidden Atomic Lines in Auroral Spectra', by D. R. Bates.

The modern theory of low-energy electron collisions with complex atoms and ions may be traced to Seaton's 1953 classic study of the Hartree-Fock equations for continuum states and his application of them to calculate transitions between the 3P, 1D, and 1S terms of the ground-state configuration of atomic oxygen. The calculations on atomic oxygen were extended to O II and N II and N I, providing the first-time quantitative estimates of the electron impact excitation and de-excitation of the forbidden lines of the ground state configurations for these systems. These results were of fundamental importance in many applications, e.g., forbidden atomic lines in auroral spectra and gaseous nebulae, as illustrated by the aforementioned articles of Bates and Flower. Seaton's theory required the solution of sets of coupled integro-differential equations for the motion of the scattered electron. Since it was not possible to solve these equations exactly, Seaton developed approximate methods of solution and obtained results very close to the later exact numerical ones. Following the development of the general theory of e-H excitation by Ian Percival and Seaton, the latter initiated in late 1956 the intensive effort at UCL required to solve the resultant equations. This led to the general computer programme for e-H scattering on the English Electric Pilot ACE and DEUCE computers by Phil Burke, his wife Valerie, Percival and R. McCarroll. In the late sixties Seaton decided to exploit the new generation of computers to obtain accurate data on atomic structure and atomic collisions for application to the interpretation of solar spectra acquired by rocket and satellite launchings. Most of the lines arose from electric dipole transitions in highly ionized atoms. The corresponding collision strengths could be calculated with sufficient accuracy in the distorted-wave approximation provided good bound-state functions were produced; these functions would then also allow transition probabilities and oscillator strengths to be calculated. The outline of such a project in 1967 led to the programme, STRUCTURE, for calculating atomic wave functions by his colleagues, W. Eissner and H. Nussbaumer, in 1969. The extension of STRUCTURE to include relativistic corrections to the energy levels by M. Jones and the further extension allowing the calculation of transition probabilities by Eissner and Nussbaumer resulted in SUPERSTRUCTURE. Hannelore Saraph developed the programme SIMMEG in the late sixties for the transformation of reactance matrices calculated in LS coupling to collision strengths, and then JAJOM for such use in intermediate coupling. In their 1972 paper on computer programmes for calculating electron-atom collision cross-sections, Eissner and Seaton were mainly concerned with the excitation of neutral atoms and positive ions at near-threshold energies for astrophysical application, two approximations being discussed. The distorted wave approximation was applicable when the coupling of the integro-differential (ID) equations is not too strong, i.e., for highly ionized systems (in practice for more than about two or three times ionized). The ID approximation (often called the 'close-coupling' approximation) could be used when the DW method failed. A prototype version of IMPACT, a general computer programme based on numerical methods to replace the ID equations by a system of linear algebraic equations, was working in 1969, but the final version was not published until 1978 by M. A. Crees, P. M. H. Wilson and Seaton. Other programmes in the UCL package include PHOTUC written by Hannelore Saraph to calculate photoionization cross-section from solutions of the close-coupling equations, and RANAL, originally written by Seaton, for fitting calculated reactance matrices as functions of energy and the extrapolation and interpolation of scattering data. Throughout the package programmes were written for certain types of problems and not particular cases, Seaton's intention being to get away from the "one man - one cross-section" approach to programming. The departmental list of publications for the 1954-55 session, which he spent in Paris, records twelve papers by Seaton, three being in Comptes Rendus. Two of the three papers in Comptes Rendus were on the approximate calculation of atomic photoionization cross-sections, the second being his first publication on quantum defect theory. Then in 1958 he extended the theory to continuum states, providing a basis for general formulae for radiative transition probabilities applicable to singly excited states. There followed the extension to bound-free transitions by A. Burgess and Seaton, giving their general formula for calculating atomic photoionization cross-sections, and the general formula of Gillian Peach for the calculation of absorption cross-sections for free-free transitions in the field of positive ions. She revised the Burgess-Seaton formula, and wrote a general computer programme, which was available on request, for calculations on the basis of her general formula. Then in 1971 she published extensive results for continuous absorption coefficients for non-hydrogenic atoms. Detailed comparisons of the results of the Peach programme and the close-coupling method for photoionization were made for O IV by Hannelore Saraph showing agreement to within 10% for the background cross-section from states 2s2nl, including nl = 2p, and from 2s2pml states the Peach formula results were not generally reliable for ml = 2p, but quite good for m > 2. Although the one-channel theory was very successful for calculating photoabsorption rates, it soon became evident that a multi-channel theory, applicable to systems with more than one electron in open shells, was required for interpretation of a wider range of phenomena. The first paper on multi-channel defect theory appeared in the Proceedings of the Third International Conference on the Physics of Electronic and Atomic Collisions held at UCL in 1963, the authors being O. Bely, Moores and Seaton. There followed a series of thirteen papers, QDT I-XIII, by Seaton and his collaborators between 1966 and 1982, deriving powerful interpolation and extrapolation techniques to describe perturbed Rydberg series and complicated resonance structures. In QDT I Seaton generalised the theory to the many-channel case and included a number of new results, and in QDT II he gave some illustrative examples of applications of one-channel and two-channel problems, an improved value being obtained for the ionization energy of He. QDT III by Bely dealt with the scattering of electrons by He⁺ with some inclusion of the effects of the dipole coupling potential in the analytic description. In QDT IV Moores applied the many-channel theory to the calculation of radiative transition probabilities and photoionization cross-sections of Ca, including the effects of autoionizing states. A semi-empirical method was applied, using experimental data for the perturbed series. QDT V by Moores was concerned with the autoionizing and bound states of Be. N. A. Doughty, V. B. Sheorey and Seaton extended the theory to extrapolations along isoelectronic sequences in QDT VI. Seaton in QDT VII developed the theory for the analysis of complex resonance structures in inelastic electron-ion scattering, obtaining expressions for the widths and positions of resonances and for the cross-sections averaged over resonances in regions just below the excitation thresholds. In QDT VIII P. de A. Martins and Seaton considered resonances in the collision strengths for O⁺ 2p³²D_3/2-²D_5/2. D. W. Norcross and Seaton introduced the concept of a complex quantum defect and applied it to an analysis of the Be spectrum in QDT IX. The many-channel theory was applied to the problem of the calculation of photoionization cross-sections, including detailed resonance analysis, in QDT X by J. Dubau and J. Wells. In QDT XI Seaton gave a summary and clarification of the development of the theory and clarification of some of its aspects. Dubau in QDT XII extended the theory for cases of dipole coupling potentials, overcoming the problems encountered in QDT III. In QDT XIII Dubau and Seaton gave further consideration to autoionization processes in excitation and photoionization processes of importance in the study of dielectronic recombination.

In 1957 Seaton with Ian Percival gave the first rigorous treatment of the partial-wave theory of electron-hydrogen collisions and in 1960 they collaborated with Leonardo Castillejo in the consideration of the theory of the long-range interactions between electrons and hydrogen atoms, showing that the leading term of the interaction at large separation was a/(2r⁴), where a is the static dipole polarizability of hydrogen. Then in 1977 Seaton with L. Steenman-Clark showed that the next long-range term was a'/(2r⁶), where a' is linearly dependent upon the energy of the elastically scattered electron and can be calculated analytically; this was followed in 1978 by a numerical study of the non-local nature of the effective potentials for electron-hydrogen scattering. In her comprehensive review of interactions in atoms and diatomic molecules, Gillian Peach cites two of her own papers, namely (i) a consideration of the model potentials involved in low-energy scattering of excited helium atoms by rare gases (1978) and (ii) an examination of the relative merits of model potentials and pseudopotentials and their application to problems of atom-atom scattering (1982), as illustrations of her particular interest in the two-centre system.

In his 1955 paper on cross-sections for 2s-2p transitions in H and 3s-3p transitions in Na produced by electron and proton impact Seaton pointed out that, when the energy of DE of a transition is much less than the mean thermal energy kT, the rate coefficient for proton impact excitation of neutral targets is greater than that for electron excitation by a factor equal to the square root of the ratio of the proton to electron mass. Thus proton collisions are effective in redistributing angular momenta in high-lying Rydberg levels. In 1962 Seaton applied the impact parameter method to obtain cross-sections for optically allowed transitions by electrons. It consists of a series of approximations that provides simple analytical forms and is therefore particularly suitable to collisions involving highly excited states, the results within their range of validity being adequate for many astrophysical and other applications. In 1964 there followed three papers on recombination spectra: (i) R. M. Pengelly solved the capture cascade equations for a hydrogenic system in the limit of low densities, but the agreement with observations in planetary nebula were unsatisfactory, leading to the conclusion that l-changing collisions should be taken into account; (ii) Pengelly and Seaton calculated the cross-sections for such collisions using a modified form of the impact parameter method; and in (iii) Seaton used them in a further study of recombination spectra. In the excitation of positive ion targets the Coulomb interaction diminishes the rate coefficients for proton impact while enhancing those for electron impact. In (ii) it was shown that for collisions involving l-changing of He⁺ by protons the effects of the Coulomb interaction were small for large values of n at the temperatures of the order of 10⁴ K, characteristic of astrophysical plasmas. In 1964 Seaton also investigated the proton impact excitation of coronal lines, showing that the excited fine-structure level, Fe¹³⁺(3p²P_3/2), may radiate with the emission of the coronal greenlineat 5304.3 Å. He showed that the proton excitation rate exceeds the electron excitation rate at temperatures above 1.3 x 10⁶ K. At the end of his article Dalgano points out that although most of Seaton's research has involved electron impact phenomena it was his aforementioned studies that established the importance of proton impacts with the ionized constituents of astrophysical nebulae and laboratory gases and initiated a lengthy series of calculations, particularly on proton-impact excitation of fine-structure transitions, which broadened to include metastable transitions and ionization processes, all of which participate in determining the ionization structure and the emissivity and energy loss from hot plasmas. Work by the group on gaseous nebulae started with the extension of Seaton's 1953 calculations on atomic oxygen to O II and N II and then to N I providing for the first time quantitative estimates of the electron excitation and de-excitation of the forbidden lines of the ground state configurations of these systems. This was followed by his work on the relative line intensities for [O II] and [S II] ²D to ⁴S; the interpretation of the Orion spectra; and the relative [O II] intensities (with Osterbrock). On the planetary nebulae there were papers on electron temperatures and electron densities; local density variations; and continuum intensities. The sixties started with his paper on H I, He I and He II intensities, and that on the ultra-violet radiation field of the central stars (with Hummer). There followed eight papers on the ionization structure of planetary nebulae: (i) pure hydrogen nebulae; (ii) collisional cooling of pure hydrogen; (iii) the ionization of helium (Hummer & Seaton); (iv) optical thickness of the nebulae and temperatures of the central stars ( R. J. Harman & Seaton); (v) radii, luminosities and problems (Seaton); (vi) the Lyman continuum problem (D. van Blerkom & Hummer); (vii) the heavy elements (Flower); and (viii) models of NGC 7662 and IC 418 (Flower). A joint paper with Harman obtained for the first time a well-defined track for the central stars on the Hertzsprung-Russell diagram, the final stage of evolution of these exceptionally hot stars being down to white dwarfs, and processes involving neutrino emission probably being responsible for the rapid evolution of the stars. Other papers by Seaton involved excitation of spectrum lines in nebulae by resonant scattering of radiation from the central stars; recombination spectra of gaseous nebulae; abundance of He in gaseous nebulae; distances of planetary nebulae; forbidden line radiation from gaseous nebulae (with Flower); and electron densities in planetary nebulae (with Saraph). With M. Brocklehurst he made a study of radio recombination lines emitted by gaseous nebulae taking into account all relevant collisional and radiative processes, including maser action and pressure broadening. Results calculated on the basis of a spherically symmetric model constructed for the Orion nebula agreed with radio observations. Then with M. Salem he considered the interpretation of continuum flux observations from thermal radio sources, covering continuous spectra and brightness contours, leading to the consideration of three-dimensional models by Salem and the construction of another spherical one for the Orion nebula, which was compared with the previous one. Brocklehurst and Salem wrote a computer programme for the calculation of the intensities and profiles of helium and hydrogen radio recombination lines emitted by a thermal source.

The ionization balance in high temperature plasmas was shown to be very strongly affected by the process of dielectronic recombination. By studying the behaviour of a large number of specific cases a simple general formula was obtained for the estimation of dielectronic recombination rates in low-density plasmas such as the solar corona by Burgess. He also considered dielectronic recombination and the temperature of the solar corona, and, with Seaton, discussed the ionization balance for iron in the solar corona. Their success in explaining the ionization structure of the solar corona led to dielectronic recombination being usually associated with coronal conditions in which collisions dominate ionization and the electron temperature corresponds approximately to the temperature of maximum abundance of the emitting ion. Later Storey carried out calculations to investigate the contribution of dielectronic recombination to line excitation and ionization balance under conditions where the temperature is far too low to cause collisional ionization. The calculation of dielectronic recombination coefficients, bringing together electron scattering, bound-free and bound-bound radiative processes, embodied in one process all the problems that the UCL computer package was designed to solve. The calculated rate coefficients for dielectronic recombination of a number of ions of C, N, and O were found to exceed the corresponding radiative recombination coefficients at T_e = 10⁴ K. P. C. W. Davies and Seaton gave a rather general formulation of dielectronic recombination, essentially a generalisation of radiation damping theory, which laid the basis for its development by rigorous quantum mechanical theory, which was carried out by R. H. Bell and Seaton.

Seaton became keen to make astronomical observations and agreed to interchange posts for a year with D. E. Osterbrock. Osterbrock came to UCL for the 1968-69 session and his interpretation of the observed Fe X and Fe XIV lines in Seyfert Galaxies was the first publication using the distorted wave approximation; he also calculated C III collision strengths for the excitation of semiforbidden lines in quasars and nebulae. It was not until ten years later that Seaton started to make observations with the IUE, but soon made up for lost time, collaborating in ten papers between 1978 and 1981 which included observations of novae and nebulae with theoretical interpretations. With J. I. Castor and J. H. Lutz a detailed analysis was made for the central star NGC 6543 finding stellar wind velocities as high as 2100 km/s and mass loss rates greater than five times that attributable to radiation pressure alone. Nova Cygni 1978 was observed for 300 days from the fourth day after the outburst on 7 September 1978. The spectra obtained included emission lines of He II, C II, III and IV; N II, III, IV and V; and O I, II, IV and V. Seaton and his colleagues (D. J. Stickland, C. J. Penn, M. A., J. Snijders and P. J. Storey) analysed the results, finding 88 days after the outburst an electron concentration of 8 x 10¹³ m^-3 and electron temperatures ranging from 9500 K derived from the ionization balance for C III to 14,000 K from that for N V. The derived abundances of He, C, N and O showed that those of the three heavier elements were much greater than in the sun, especially that of N. This was understandable on the basis of production of the nova by a runaway nuclear reaction leading to ejection of a shell of material. Seaton was also involved in two of the best studied nebulae, namely NGC 7662 and IC 418. In an exhaustive study of NGC 7662, J. P. Harrington with Lutz, Stickland and Seaton considered the reasons for the discrepancies between determinations of the temperature of the central stars based upon the Zanstra method and upon UV continuum observations. They recorded 24 UV line intensities ranging from the N V l1240 line to the He II l3203 line. Abundances of C, N, O and Ne relative to H were obtained on the basis of sophisticated models incorporating all the important physical processes after careful attention to the reduction of the UV observations of both the nebula and the central star. The C III l2297 was interpreted as being produced by dielectronic recombination of C³⁺ via low-lying autoionizing states with the consequence that C/O > 1. A C³⁺ abundance derived from the intensity of l2297 and a total C abundance almost twice larger than the value deduced from the intensity of the collisional excited resonance line doublet C IV l1550 led to the conclusion that l1550 undergoes dust absorption. Only an upper limit being established for the intensity of Mg II l2800 implied an abundance of magnesium at least 50 times less than the solar value; silicon is also depleted by a factor of c. 4 owing to both elements having been removed from the gas phase by grain formation. Measurements were made of the UV line intensities of C⁺, C²⁺, O⁺ and Mg⁺ in IC 418 and values of the carbon and carbon ionic abundances were derived from the observed intensities of the l2326 and l1908 relative to Hb and measurements of the O III and N II electron temperatures. There was good agreement with the values of total carbon abundance obtained by Torres-Pembert et al but differences in the abundances of individual ions. Both groups of workers found an enhancement of the C/O ratio of IC 418 compared with that of the sun. They also noted that the observed C⁺/C²⁺ ratio was significantly greater than predicted by model calculations. The inclusion of dielectronic recombination in the calculations on IC 418 would tend to bring the two ratios into better agreement.

Seaton's expertise in computing was recognised by his appointment as a member of the "Flower's Committee" which investigated the future needs of computing equipment in British universities; its report, accepted by the Government in 1966, resulted in major changes and led to the Computer Board, setting the pattern for the next twenty years. He served as Chairman of the UCL Computer Board of Management for some ten years, and was a member of the Board of Management of the University of London Computer Centre and of the University's Central Coordinating Committee for Computing Services. For UCL his efforts in 1965 were largely responsible for the installation of the IBM 360/H65 computer at the College with provision for its use by other Colleges. He served as Acting Head of department when Heymann had a sabbatical year at CERN. In 1968 he played a major role in establishing and supporting the international journal Computer Physics Communications, both as an Advisory Editor and contributor of programmes. He was involved in launching the Journal of Physics series in 1968 and became the first Honorary Editor of the B series on Atomic and Molecular Physics. His elections to the Fellowship of the Royal Society in 1967 and UCL in 1972 were followed by the award of the Honorary Doctorate of the Observatoire de Paris in 1976, the Presidency of the Royal Astronomical Society in 1979-81, the award of the Honorary D. Sc. degree by the Queen's University of Belfast in 1982, the Royal Astronomical Society Gold Medal in 1983, and the Guthrie Medal of the Institute of Physics in 1984. Gillian Peach joined Seaton's group as a Research Assistant in October 1960, having graduated and obtained her Ph.D. degree at Royal Holloway College; she became a Lecturer in October 1966. Having gained an international reputation as a theoretical atomic physicist with special interests in astrophysical applications of the theory of atomic collision processes, she became a Reader in the 1983-84 session. Her comprehensive work in the field of ionisation of atoms and atomic ions by electron and proton impact covered all atoms from hydrogen to argon as well as some iso-electronic sequences; in many cases her results were the first on these ionization cross-sections. Later the data found a wide range of applications by others ranging from the interpretation of features of the atmosphere of Io to processes of interest in energy production in thermonuclear fusion.

The development of general formulae based on quantum defect theory for the photo-ionization and free-free absorption of photons by atoms and atomic ions enabled cross-sections for particular cases to be obtained simply by the insertion of known spectroscopic data for the appropriate atomic system. This work was widely applied to provide estimates of the many thousands of cross-sections required in astrophysical problems. Her extensive tables of continuous absorption coefficients for non-hydrogenic atoms were widely utilized by astrophysicists in the interpretation of stellar spectra.

In the field of the theory of the broadening and shift of spectral lines by pressure effects she covered the first fully quantum-mechanical treatment of the pressure broadening of an atomic spectral line by electron collisions; this required a synthesis of the impact theory of line broadening with the close-coupling approach and the many-channel quantum defect theory for electron-atomic ion collisions.

She developed good model and pseudo-potentials as well as extensive computer programmes for application in the field of low-energy atom-atom interactions. Her article in honour of Seaton's sixtieth birthday is a 58-page review, of the then-current status of the field of long-range interactions in atoms and diatomic molecules.

David Moores entered the Department in October 1959 and on graduation started research on applications of many-channel quantum defect theory under the supervision of Seaton, gaining his Ph. D. degree in 1965. From 1965-67 he was a Research Assistant in Ian Percival's group in the Department of Mathematics at Queen Mary College. His research was undertaken mainly at UKAEA, Harwell in collaboration with Phil Burke; they carried out one of the first accurate calculations of electron-impact excitation of positive ions. He returned to College in 1967 as a Lecturer, joining Seaton's group, and gaining promotion to the Readership grade in the 1984-85 session for his research in theoretical atomic physics, a distinctive feature being work on problems closely related to experimental work.

Following his collaboration with Burke, Moores developed techniques for the computation of scattering amplitudes and various parameters of great value to experimentalists, and that led to studies of electron scattering by alkali atoms and the related problem of photo-detachment from alkali negative ions. Much of the interest in the work arose from developments in laser technology which enabled the detachment cross-sections to be measured with high precision and resolution. Comparison of the theoretical and experimental results provided a good check on methods applied in a wide range of problems in theoretical atomic collision physics.

Some of his most original work was concerned with the electron scattering by molecular systems. The multi-centre nature of molecular systems leads to slow convergence with the commonly used single-centre expansions of the atomic-system type. Moores noted that it is possible to obtain exact electronic wave functions for the simplest molecule, the positive hydrogen molecular ion, using prolate spheroidal co-ordinates, and he showed that the use of such co-ordinates led to greatly accelerated convergence for electron-molecule scattering.

Much of his then most recent work was concerned with electron impact ionization of atoms and atomic ions, the theory of which is very difficult owing to the need to allow for correlations between two electrons in the continuum. Rates for impact ionization were urgently required for studies of laboratory and astrophysical plasmas; experimental results were available for some ions, but for many one had to rely on calculated values and various semi-empirical approaches. The distinguishing feature of Moores's work in this field was to make accurate ab initio calculations for complex atomic systems, calculations greatly superior to any previous ones. His 45-page article with Hannelore Saraph in honour of Seaton's sixtieth birthday follows the evolution of quantum defect theory and its applications from the 1960s, the emphasis being on work inspired by developments at UCL.

High Energy Physics Group

This group was really formed in 1960 when James Hamilton came from Christ College, Cambridge to take up the second established chair in the department. His interests had been particularly in the theoretical side of nuclear physics and fundamental particles, and he was the author of the book on "The Theory of Elementary Particles", published by the Oxford University Press, 1959. However he left at the end of the 1963-4 session for a Professorship at the Nordic Institute for Theoretical Physics in Copenhagen. Meanwhile he had established a thriving group studying low-energy pion-nucleon scattering and pion-pion interactions, sponsored in part by the Air Force Office of Scientific Research, OAR, through the European Office, Aerospace Research, United States Air Force. By the time he left, the group consisted of two lecturers, Drs. A. Donnachie and W. S. Woolcock, two research assistants, Drs. A. T. Lea and G. C. Oades, and seven research students. Incidentally Woolcock came to UCL with Hamilton to complete the last year of his Ph.D. degree, being given leave of absence from Cambridge University; he was appointed lecturer at UCL in 1963, having in the meantime being lecturer in the Mathematics Department of the University of Queensland. Donnachie returned to Glasgow in 1996, having spent his last session on leave at CERN. Leonardo Castillejo returned in January 1967 to take up the chair left vacant by Hamilton's departure to Copenhagen and become head of the group. Dr. Zienau and research students, H. Osborn and P. Cordero, moved over from the General Physics Theoretical Group, and Drs. C. Wilkin and B. R. Martin joined the group as lecturers in 1968. Woolcock left in 1968 to take up an appointment at the Institute of Advanced Studies, Australian National University, Canberra. A method was developed for obtaining information about pion-pion interactions from low-energy pion-nucleon scattering based on the dispersion relations for the partial p-N amplitudes. It was shown how low-energy s-wave p-N scattering could be broken down into its constituent contributions from T=0 and T=1 p-p interactions, core (short-range) effects, crossed a₃₃ resonance effect, and rescattering. Then the same was done for the p-wave p-N scattering but with the addition of the long-range Born term. The p-wave p-N breakdown showed that the position of the (3/2,3/2) resonance could not be calculated without taking the T=0, J=0 p-p interaction as well as the short-range attraction. T.D. Spearman, P. Menotti, G. C. Oades and L. L. J. Vick collaborated with Hamilton in these researches, Oades and Vick being UCL research students. In a 50-page article (Rev. Mod. Phys., 35, 737,1963) Hamilton and Woolcock give an account of the application of single variable dispersion relations to calculate the main parameters of low-energy pion-nucleon scattering and the low-energy phase shifts, the input data being information on the total cross-sections and the dominant resonances of the p-N system. They discuss in particular the high-energy behaviour, the subtractions and sum rules in the application of dispersion relations, as well as the convergence of the Legendre series for the expansion of scattering amplitudes in the partial waves. The rates of convergence are of basic importance for the prediction of low-energy pion-nucleon phase shifts by dispersion relations. An account is also given of Woolcock's calculations in his 1961 unpublished Cambridge Ph.D. thesis, and other determinations, of the parameters of low-energy pion-nucleon physics. Finally the fixed momentum-transfer dispersion relations are used to predict the s-wave and p-wave pion-nucleon phase shifts at low energies.

On the photodisintegration of the deuteron, Donnachie and P. J. O'Donnel extended the former's 1961 calculations of the differential cross-sections and polarizations for photon laboratory energies up to 130 MeV by including more transitions, final-state couplings and investigating retardation effects. The results were found to be insensitive to the deuteron D-state probability but markedly dependent on the omission or inclusion of retardation, even at low energies. Detailed comparison with experiment showed that the best fit over the whole energy range to the available data was achieved with a 6% deuteron D-state probability and with retardation included. The deuteron photodisintegration process was used to study nucleon-nucleon phase shift parameters. In the photoproduction of pions from nucleons, Donnachie and G. Shaw used fixed-momentum dispersion relations to evaluate transition amplitudes which lead to final s-, p- and d-wave scattering states. Using pion-nucleon scattering phase shifts up to 700 MeV, the coupled integral equations for the dominant M₁₊, E₀₊ transitions were solved explicitly by an iterative method. Good agreement with experiment was obtained up to 550 MeV photon laboratory energy and a much better determination was made of the g-r-p coupling constant. Donnachie and Hamilton developed a variational method of solving p-N dispersion relations, an application of the method confirming an earlier analysis of s-wave p-N scattering. With Lea they developed a peripheral method, in which the very-short-range part of the interaction was almost completely suppressed, for predicting p-N phase shifts up to moderate energies. Precise values were given for the p-, d-, and f-wave phase shifts, with the exception of p₁₁, up to 400 MeV, and the general behaviour reproduced up to around 1 GeV. The 600- and 900-MeV p^--p resonances were identified with the D13 and F15 amplitudes respectively, and the 1.35 GeV p⁺-p resonance probably in F₃₇.

Donnachie and Lee collaborated with P. Auvil and C. Lovelace of Imperial College in a phase-shift analysis of pion-nucleon scattering up to 700 MeV, finding a phase family in the 300-700 MeV region in excellent agreement with practically all the experiments, and also with predictions from partial wave dispersion relations.

Using the techniques of energy-independent phase shift analysis, with simultaneous fitting to the partial-wave dispersion relations, Donnachie, Lea and Lovelace obtained a unique solution to p⁺p scattering below 1100 MeV pion laboratory energy. The most striking feature of this solution was that the main content of the 800 MeV shoulder was an inelastic S₃₁ resonance, such an object being required by SU(6) in the 70^- multiplet to which the known D₁₃ resonance belongs. Donnachie, Kirsopp and Lovelace carried out a sophisticated analysis of low energy experimental results, including those of the UCL spark chamber group, on p elastic scattering. On the basis of phase shift analyses at 59 energies, linked with partial wave dispersion relation fits,18 nucleon resonances were proposed in the mass range 1236-2265 MeV, 9 in the range 1680-2190 MeV being new ones, all with very small branching ratios to the elastic channel.

Donnachie and Hamilton showed that the quantum numbers of the 200, 600, 900 MeV and 1.35 GeV nuclear isobars are determined by the systematic properties of the longer range part of the pion-nucleon interaction, thus making possible the understanding of the Regge plot in terms of the interactions which produce the several families of isobars. They also showed that the requirement of dispersion relations for partial-wave amplitudes to obey a high-energy boundary condition gave rise to a unitary sum rule, which could be used to estimate the short-range parts of the pion-nucleon interaction. This made possible accurate predictions of the non-resonant p-, d- and f-wave p-N amplitudes up to around 650 MeV in good agreement with an analysis of experimental data.

The partial-wave expansions of invariant amplitudes for various scattering processes involving spin ¹/₂ particles were studied by Woolcock and G. Rasche using a general representation for the Dirac gamma matrices. They extended the study to cover the general formalism of some scattering processes involving photons and investigated ambiguities in the solution of partial-wave dispersion relations in which the left-hand cut contribution is approximated by a finite set of poles. Woolcock showed that the necessity for subtractions in dispersion relations in order to make the integral over the left-hand cut converge implies an oscillatory behaviour of the discontinuity across that cut, the violence of the oscillations increasing with the number of subtractions. He investigated the properties of dispersion integrals (Stieljes Transforms), firstly obtaining results for their asymptotic behaviour for large z and then extended them to prove theorems holding uniformly for all directions in the complex plane. Special additional assumptions, to hold for all sufficiently large values of the argument of the function, were required to obtain the extended results.

G. D. Froggatt made an analysis of the Regge Pole Model for Vector Meson production with G. V. Dass (from RHEL), considering the reaction pN -> eN and then KN -> K^*N. An analysis of (+-) dipion production, which indicated that the extrapolated production cross-section did not vanish at t=0 as it would for pure one-pion exchange, led him and D. Morgan (RHEL) to propose a model for the phenomenon, giving a new prescription for performing Chew-Low extrapolations. The Reggeized Deck amplitude for the pN -> prN reaction was partial-wave analysed in the A₁ region of the pr subsystem by Froggatt and Gisela Ranft (on attachment to the group from RHEL). It was found that the state was predominantly 1⁺ s-wave, in agreement with a local duality interpretation, and this was followed by a general discussion of the spin-parity structure of a two-particle subsystem for a double-Regge expansion of a three-body production amplitude. Gisela Ranft then published four papers on a review of the current evidence for multi-Regge pole processes: the annihilation reaction p + p -> 2p⁺ + 2p^- and a multi-Regge model; the double-Regge model and an 'anticornering' effect in three-particle production processes; and a double-Regge analysis of the reaction K^-p -> K^-wp.

A study of composite particles in field theory was undertaken resulting in the following papers: 'Z=0 and compositeness', 'Poles of the two-body Green function', 'Conditions for composite particles with special reference to Lagrangian field theory', 'Relativistic centre of mass variables for two particle systems with spin' and 'Relativistic corrections to non-relativistic two particle dynamical calculations - demonstration of the validity of the Drell-Hearn-Gerasimov sum rule for weakly bound composite particles' by Osborn; 'Equivalence of the Lee and Zachariason models' by Osborn and Zienau; and 'Conditions for compositeness in field theory' by Cordero.

Castillejo received his early education at the international schools in Madrid and Geneva, his family leaving Spain during the Civil War. A year at the Polytechnic in Regent Street, followed by one at Imperial College, resulted in the award of the B. Sc. degree in engineering in 1942. After four years of work on the land, he entered King's College, Cambridge, gaining the B. A. degree in mathematics in 1948. He then joined UCL as a Research Assistant in the Mathematics Department under Massey working on high-energy (83 MeV) nucleon-nucleon scattering and became an Assistant Lecturer in physics in 1950 when Massey assumed the headship of the department. During a year's leave of absence as a U. S. Foreign Aid Administration Fellow at Cornell University in 1954, he collaborated with Dalitz and Dyson on what was to became known as the Castillejo-Dalitz-Dyson ambiguity, which had a major impact on the application of analyticity and bootstrap ideas to particle physics in the 1960s. They realised that it was possible to add arbitrary poles to the denominator function of a scattering amplitude without creating extra singularities in it. In a sense such poles express the physical possibility that stable particles are present even when the interactions are switched off. In 1957 when P. Matthews left Birmingham to join A. Salam at Imperial College, Peierls approached Massey to persuade Castillejo to move to Birmingham at rather short notice. In 1963 he went to Oxford with Peierls, becoming a Fellow of Wadham College. When Massey approached Peierls in 1965 about Castillejo returning to UCL to fill the chair vacated by Hamilton, Peierls wrote "...I am, of course, very distressed about the proposal since I have greatly valued having Castillejo here and would greatly deplore losing him....he would be an excellent person to meet the requirements of the post as described in your letter. He is knowledgeable, energetic, and passionately interested in physics though, of course, along somewhat different lines from Hamilton's; he is excellent and kindness itself with students, and very interested in problems arising from experiments. His chief disability, as no doubt you know, is that he does not publish very much - partly because of his high standards, which make it very hard for him to be completely satisfied with his own results, and partly because he is always so willing to help other people with their problems and worries that he often disregards things which would bring him the greater personal credit. However, this tendency is a disadvantage to him personally and not to the Department to which he belongs." By the time he returned to College, the Annual Reports had listed just two papers, namely the famous CDD one (1955) and the one in atomic physics with Percival and Seaton on exchange effects in the elastic scattering of electrons from hydrogen, formulating the problem in the more consistent time-dependent approach (1960). The next listings were two 1973 papers, the first with B. J. Berriman on 'Comparison of eikonal amplitudes for potential scattering' and the second, the somewhat surprising 'Are there real limits to growth? - A reply to Beckerman,' in the Oxford Economic Papers, 23, with L. S. Brown, H. F. Jones, T. W. B. Kibble & M. Rowan-Robinson. Some six years later, on leave at the State University of New York at Stony Brook, he wrote a paper on 'Little-Group Classification of Gauge Fields', with M. Kugler & R. Z. Roskies in which was proposed a new way to treat the classification of the Yang-Mills gauge fields at a space-time point, the main tool being a consideration of the structure of the Little group which left the field invariant; this approach reproduced the standard classification of the Weyl tensor and of the electromagnetic field. This was followed by he and Kugler investigating a class of solutions of the classical SU(2) Yang-Mills equations, the symmetry of which prescribed a natural set of gauge-invariant degrees of freedom. Meanwhile at Stony Brook he had published a paper on 'Optimal and nearly optimal distribution functions for ⁴He', with A. D. Jackson, B. K. Jennings & R. A. Smith, in which the properties of the Euler-Lagrange equation obtained by minimizing the hypernetted-chain energy of a boson fluid were studied. A consideration of the asymptotic form of the resulting two-body distribution function g(r) showed that g(r)^-1 was proportional to r^-4 for short-ranged potentials; the stability conditions for g(r) were expressed as an eigenvalue problem and the relation to the adiabatic compressibility was established. Previous numerical results for liquid ⁴He were shown to describe an energy minimum. The existence of the low-lying eigenvalues for all l and the nature of the related non-spherically symmetric eigenfunctions suggested the existence of 'crystalline' solutions of the Euler-Lagrange equation. Castillejo then began working on rather specialist esoteric models, closely linked to the more fashionable areas of modern particle theory, much of this work being carried out with Andrew Jackson from Stony Brook. First there was the case of the toroidal nucleus - a doughnut model of a nucleus of 150 quarks which might have a lower energy than a spherical model - the so-called anomalon. Another topological problem was the Skyrme model of the nucleus, in which he investigated the nucleon-nucleon interaction and played an important role in establishing its connection to more familiar meson exchange interaction. Interest in the phase structure of the Skyrme model and its connection to chiral symmetry restoration led to a more general investigation of collective co-ordinates in effective field theories, possible connections to high-temperature superconductivity fascinating him.

Castillejo's undergraduate lectures frequently perplexed the audience owing to his habit of deriving new proofs on the blackboard, yet his tutorials were excellent. The 1976 Departmental Booklet for distribution to schools included a photograph of him with four undergraduates, tutor and students all smiling, during a tutorial on relativity, the caption being 'Someone has spotted the deliberate mistake in the formulae on the blackboard.' He was an excellent supervisor of postgraduates, readily stopping his own work to sort out their problems. After retirement he remained in the department and started demonstrating in the first-year laboratory, critically examining all the scripts. After graduating and obtaining his Ph. D. degree at Birmingham University, Colin Wilkin spent the next two years as a Research Fellow at CERN and then in 1965 proceeded to the Brookhaven National Laboratory, USA, as a Research Associate, working on the interpretation of the Brookhaven K⁺-p(d) total cross-sections, followed by participation with an experimental group measuring the angular distributions with spark chamber and counters. He joined Castillejo's group as a Lecturer in 1968. A theoretical physicist with a critical insight into lots of experimental problems and the ability to explain them in simple terms, he was appointed Reader in the 1973-4 session on the basis of his work on a variety of topics - analytic properties of scattering amplitudes, particle symmetries, Eikonal approximations and interaction of elementary particles with nuclei, having become one of the foremost experts in the latter two fields. Many experimental groups throughout the world consulted him for explanation and analysis of their results and suggestions for the direction that their next experiments should take, both high-energy experimental groups at UCL benefiting from his collaboration. His expertise in lecturing led to many invitations to participate in summer schools and his fluency in French being a real asset. At the time of his promotion he was working on the coherent production of particle resonances from nuclei to study the resonance-nucleon cross-section (with the UCL spark chamber group); low energy pion-nucleus scattering and its interpretation in terms of Glauber theory and optical potentials; Coulomb effects in p^+/- nucleus total cross-section measurements, and tests of charge symmetry ; and three-body studies in one dimension.

In the late sixties he collaborated with R. H. Bassel in the multiple scattering interpretation of the experiment involving high-energy (1.7 GeV/c) p - a scattering by H. Palevsky et al at the Cosmotron. Then they analysed elastic and total cross-sections of 1 GeV protons on H², He⁴, C¹² and O¹⁶, in conjunction with the corresponding electron scattering measurements, on the basis of Glauber's high-energy approximation, leading to information unobtainable from the electron data alone. Elastic pion-deuteron scattering at 3.65 and 3.75 GeV/c was analysed with C. Michael on the basis of Glauber theory, particular attention being paid to the deuteron D-state and to the spin dependence and phase variation of the pion-nucleon amplitudes; the good overall agreement between theory and experiment could be improved with a larger value of the deuteron quadrupole form factor than that given by a Hamada-Johnston type of wave function. The Glauber theory of multiple scattering was used by Wilkin and N. Straumann to compute the rising-mass spectrum for protons scattered off a deuterium target, the relatively clean separation of the single and double-scattering peaks making possible the determination of the high-energy p-n differential cross-section. Then with O. Kofoed-Hansen the theory was used as a basis for computations to examine the possible effects of short-range dynamical nucleon-nucleon correlations on high-energy hadron scattering on ⁴He; it was concluded that only very small effects could be expected for elastic and total inelastic scattering of commonly available projectiles. In a paper partly based on his Cambridge Ph.D. thesis, R. Smith collaborated with Wilkin in the development of a theory for large momentum transfer quasi-elastic electron-deuteron scattering using a diagrammatic technique and the derivation of expressions for those triply and doubly differentiated cross-sections which are experimentally measured; the effects of spin were included in an approximate way, and the results compared with relevant recent experiments. N. S. Craigie and Wilkin calculated the large-angle elastic, proton-deuteron, differential cross-sections at around 1 GeV from a triangle graph including as the input pp -> pd amplitude. Although the predicted cross-sections were rather low, the shape was in good agreement with experiment; a maximum in the 180 deg. cross-section was predicted for a proton K. E. of 700 MeV. Ten years later in a paper in which the deuteron stripping reaction A(d,p)B was estimated in terms of the cross-section for pion production with a proton beam A(p,p⁺)B for the same nuclear states, A and B, Wilkin extended the triangle graph model, stripping data on ²H, ³He and ¹²C being described successfully for deuteron energies of about 800 MeV. The inelastic scattering of medium-energy pions from carbon was investigated by C. Rogers and Wilkin. They also investigated in a simple model the effect of inelastic scattering on the determination of unstable particle cross-sections, pointing out that information, complementary to that obtained from forward production rates off a variety of nuclei, might be deduced from a production angular distribution off a light nucleus.

During his 1972-4 years at CERN, Wilkin was involved in a number of papers: with F. Scheck in the pion-nucleus optical potential and mesic atoms, the description of pionic atoms by a local pion-nucleus potential rather than the more conventional momentum-dependent potential was considered, it being pointed out that although in simple form they gave remarkably different answers for the energy shifts and level widths of such systems, after inclusion of the effects of short-range correlations, there was very little difference between them, the local potential requiring a slightly more positive isoscalar pN scattering length than the non-local one.

The CERN synchrocyclotron was used by K. Gabathuler, C. R. Cox, J. J. Domingo, J. Rohlin, N. W. Tanner and Wilkin in studying pion-deuteron elastic scattering near the 3-3 resonance with a scintillating target to detect the recoil deuteron. In addition to the measurement of the angular distribution for 256 MeV incident energy, the energy variation of the fixed-angle cross-section (J_lab = 160 deg.) was determined between 141 and 256 MeV. The former was in qualitative agreement with a simple multiple-scattering calculation, but the energy dependence was poorly reproduced. With Gabathuler, he analysed elastic pion-deuteron elastic scattering at medium energies on the basis of the Brueckner model, paying particular attention to the kinematic approximations that have to be made; in contrast to the earlier Glauber-type calculation, the energy dependence of the large-angle cross-section was reasonably well reproduced. Gabathuler, Cox, Domingo, Rohlin, Tanner and Wilkin were joined by E. Pedroni and P. Schwaller in a comparison of p⁺ and p^- total cross-sections of light nuclei near the 3-3 resonance, involving the measurement of the total cross-sections of ⁴He, ⁶Li, ⁷Li, ⁹Be, ¹²C and ³²S in the energy range 80 - 260 MeV in a transmission experiment; Coulomb corrections were applied using the real parts of the forward nuclear amplitudes, as determined from dispersion relations. At the lower energies there remained large residual differences between the p⁺ and p^- scattering on the isoscalar model, these being largely understandable in terms of the Coulomb distortion. Later the SIN cyclotron was used in a study of charge independence and symmetry from p⁺ and p^- total cross-sections on hydrogen and deuterium near the 3-3 resonance by Pedroni, Gabathuler, Domingo, W. Hirst, Schwaller, J. Arvieux, C. H. Q. Ingram, P. Gretillat, J. Piffaretti, Tanner and Wilkin, the total cross-sections being measured in the energy range 70-370 MeV in a classical transmission experiment using multiwire proportional chambers. The hydrogen data agreed quite well with earlier measurements. After correction for the direct effects of the Coulomb potential, the results showed energy-dependent differences of a few percent between the p⁺d and p^-d cross-sections. This charge symmetry violation could be parametrized in terms of mass and width differences between the D-isobars in agreement with the prediction of the quark model.

Wilkin investigated low-energy pion-nucleon scattering on the basis of the naive a-particle model of the nucleus in three papers, the first with J. Hufner and L. Tauscher, the second and third with J.-F Germond. By using multiple scattering formalisms in the first two papers, the p-nucleus scattering amplitudes were estimated in terms of the p-a ones. It was shown in (i) that at threshold the complex s-wave scattering lengths of the doubly-even nuclei ¹²C, ¹⁶O and ²⁰Ne could be well reproduced using a low-energy scattering theory where the scattering centres in the nucleus were assumed to be fixed and non-overlapping. However only a partial success was obtained in (ii) in describing the p - ¹²C differential cross-sections in the resonance region, 120-260 MeV, the agreement with experiment being very good at 260 MeV and getting markedly worse with decreasing energy. Hence for further investigation, in (iii), elastic p-⁴⁰Ca scattering in the region of the first pion-nucleon resonance was calculated within the optical limit of Glauber theory on the basis of the naive model, ⁴⁰Ca being the heaviest stable nucleus amenable to the simple a-cluster description. When account of the strong short-range repulsion between pairs of a-particles, the predicted cross-sections were quite close to those derived from the conventional nucleon model, though both predictions could be quite accurately parametrised as "fuzzy black discs"!

The anomalies arising from the customary analysis of the experimental data on mesic atoms and meson-nucleus scattering in terms of simple optical potentials led Wilkin to suggest that they might be due to the neglect of the energy dependence of these potentials.

With T. E. O. Ericson he showed that the virtual decay p^o -> 2g inside a nucleus, and the annihilation reactions p^- + p⁺ -> 2g or e⁺e^- on virtual pions in nuclei (the pionic analogies of positron annihilation in solids) have observable branching ratios. These processes should shed light on the micro-structure of the pion optical potential and on the nuclear pionic field with its coupling and to nucleonic excitation modes; also the e⁺e^- mode would allow the measurement of axial nuclear form factors in contrast to the fixed points of radiative capture.

In a paper on the question whether pion scattering can yield useful nuclear structure information, Wilkin pointed out that for excitations involving magnetic transitions, pion scattering should in principle allow a separation of the orbital and spin contributions whereas this was not possible in electron scattering.

D. S. Butterworth, Germond and Wilkin made estimates of the contributions of different mechanisms to the dependence of the total pion-deuteron cross-section upon the tensor polarization of the target nucleus showing that they all depend sensitively on the deuteron D-state wavefunction. At high energies the multiple scattering seemed to be the most important, the Fermi motion taking over in the resonance region, and meson-exchange current phenomena might be significant above 1 GeV/c.

Germond and Wilkin joined B. S. Aladashvili, V. V. Glagolev, M. S. Nioradze, T. Siemiarczuk, J. Stepaniak, V. N. Streltsov and P. Zielinski in explaining an observed asymmetry in the angle between the proton momentum transfer and the direction of the spectator nucleon in the break-up reaction pd -> ppn at high energies in terms of the strong (np) final-state interaction in the deuteron channel. The separable potential model for the (np) force used in the calculation of this effect also predicted the possibility of significant differences in the distributions of neutron and proton spectators, dependent upon the relative phase of the high energy pp and pn amplitudes. Then the team studied the charge exchange channel of the reaction at 1 GeV in the impulse approximation. The final-state interaction in the ¹S_o state of the pp subsystem induced a slight asymmetry in the spectator proton angle and a threshold enhancement in the pp effective mass. 20% of the observed events, which had large effective mass, could be explained quantitatively by the production of a D resonance, de-excited through a final-state interaction with the spectator nucleon. It was concluded that almost all of the small-angle np charge exchange cross-section at 1 GeV involved nucleon spin-flip.

Brian Martin, also a graduate of Birmingham, came to College in 1962 as a research student of Hamilton, and was given leave of absence to accompany him and complete his work for the London Ph. D. degree at the Niels Bohr Institute, Copenhagen, having been awarded a Ford Foundation Fellowship. A further year at the Institute, as a NATO Fellow, was followed by a two-year Research Associateship at the Brookhaven National Laboratory, USA, and a Lectureship at College in 1968. Membership of Castillejo's group led to a Readership in the 1980-81 session on the basis of an impressive list of publications dealing with the analysis of properties of two-body scattering amplitudes; the use of a wide variety of techniques ranging through phase shift analysis, dispersion relations, finite energy sum rules and duality; work on weak interactions, particularly on kaon decay; his reputation as one of the world experts on the KN system, being responsible for Section 3.2 on KN, KN, pS and pL channels in the 'Compilation of coupling constants and low-energy parameters'; and being a consultant at the Daresbury Nuclear Physics and the Rutherford High Energy Laboratories, as well as advising on the research programme at Copenhagen, where he took leaves of absence from College. He had written a book on Statistics and later collaborated with D. Morgan and G. Shaw on a comprehensive monograph on the pp system.

His first papers recorded in the College Annual Reports were two in 1968. The first concerned an investigation of the dynamics of low-energy, s-wave K⁺p scattering made by the semi-phenomenological application of dispersion relations. The amplitude in the physical region was taken from current phase-shift analyses of K⁺p scattering data and the necessary coupling constants for the exchange processes were obtained from experiment, supplemented by the use of SU(3) symmetry when experimental data was not available.The second, with E. de Rafael, involved a phenomenological description of the decays of K_L and K_S into 2g in the context of CP nonconservation. A discussion of possible measurements having a bearing on the the question of CP non-invariance suggested that the measurement of the time dependence of the asymmetry of intensities between the decays of K^o and K^o into 2g was the most promising. Then with de Rafael, J. Smith and Z. E. S. Uy some implications of nonconservation of CP invariance for the decay of K^L into m⁺m^- were discussed with reference to a recent experimental result. In the first of two papers with M. Sakitt on low-energy KN and pion-hyperon interactions, a nine-parameter K-matrix formalism for the low-energy K-p interaction was formulated and the parameters then determined by existing experimental data; in the second paper the parameters were used to obtain scattering lengths and low-energy behaviour of the s-wave KN, pL and pS amplitudes and also, through KN forward-dispersion relation sum rules, to calculate KLN and KSN coupling constants. Collaboration with A. D. Martin and C. G. Ross led to two proposals for the Y^*_o(1405) resonance, namely (i) as an s-wave virtual bound state of the KN - pSƒ system and (ii) as a CDD pole arising from high-lying channels; comparison with low-energy KN scattering data strongly favoured (i); and collaboration with Y. -A. Chao, R. W. Kraemer and D. W. Thomas in a re-analysis of low-energy KN data, made to investigate the effects of imposing constraints below the elastic threshold, showed that little information about the parameters of the L(1405) could be determined without such constraints.

With G. D. Thompson s- and p-wave K⁺p scattering below 600 MeV/c were considered, values being obtained for the s-wave scattering length and curvature coefficient by extrapolating the low-energy amplitude to threshold using a parametric form derived from a forward dispersion relation; calculations of p-wave scattering from forward dispersion relation sum rules were made in an iterative manner, starting from the pure s-wave solution of Goldhaber et al. A critical survey of K⁺p phase-shift analysis, including UCL Spark Chamber Group experimental data, was undertaken with Lea (RHEL) and Thompson, the use of forward dispersion relations to compare solutions being discussed. A quantitative analysis of the remaining solutions was made,and experiments suggested to decide between them. With C. E. Miller a phase-shift analysis of K⁺p scattering data below 1.3 GeV/c was made using parametrized partial-wave dispersion relations. Examination of the self-consistency of the solutions with backward-angle dispersion relations led to preferred solutions. In a second paper Martin discussed the role of epsilon exchange in KN scattering in relation to the above and calculated the effective e coupling constant. Martin and Miller made an energy dependent phase-shift analysis of 1660 pieces of K⁺p data below 2 GeV/c to obtain K⁺p scattering amplitudes, using the parametrized partial-wave dispersion relations, with the additional constraints of forward dispersions and p-wave scattering lengths obtained from forward dispersion sum rules, and then checking the results for consistency with backward K⁺p dispersion relations.

R. C. E. Devenish published four papers in 1972, the first with J. C. Eilbeck and D. H. Lyth on 'Calculation of the r and D trajectories'; the second with Lyth on 'Single p⁺ electroproduction at 2 GeV and the pion form factor'; and the third and fourth with Lyth and W. A. Rankin on 'Fixed t dispersion relations and the P₁₁ (1470) resonance in photoproduction' and 'Dispersion relations and the isotenor electromagnetic current in pion photoproduction' respectively. W. S. Lam published three letters in 1972, two with J. Dias de Deus on 'Duality predictions in high energy missing mass spectra' and 'Duality predictions on the ISR data of pp -> pX near the phase boundary' respectively, and the third with Chan Hong-Mo and H. I. Miettinen on 'Factorization and inclusive photoproduction'.

Martin and Devenish fitted pion-nucleon charge exchange data below 2 GeV/c using fixed-t dispersion relations and the hypothesis of two-component duality; predictions for the crossing-even amplitudes were compatible with experiment. The analysis of the p-p data was later updated to include polarization measurements and high-statistics differential cross-sections. Then with Froggatt, they made a simultaneous analysis of low-energy data for the reactions p^-p -> K^oL and K^-p -> p^oL using the hypothesis of two-component duality combined with fixed t-dispersion relations, results being given for the S^*Lp and N^*LK couplings. The low-energy amplitudes were used to evaluate FESR integrals and led to large EXD breaking for the K^*_V - K^*_T helicity flip amplitudes.

Martin and C. P. Knudsen made a phase-shift analysis, with dispersion relation sum rule constraints, of data to obtain s- and p-wave KN scattering lengths and amplitudes for both I = 0 and 1 in the very low energy region, K_L between 0 and 600 MeV/c. With F. Elvekjaer current phase-shift solutions were used to evaluate KN FESR integrals in order to examine zeros and phases of the t-channel exchange amplitudes in the most model-independent-way. K-N partial-wave amplitudes for isospin I=0 and 1 were obtained by Martin from a simultaneous phase-shift analysis analysis of K⁺p and K⁺d data in the region below 1.5 GeV/c kaon laboratory momentum. The s-wave I=0 KN scattering length was investigated on the basis of dispersion relation sum rules and evidence from measurements of KN forward differential cross-sections. Then with H. S. Groom, amplitudes corresponding to r and A₂ quantum number exchanges in K⁺-N charge exchange scattering were obtained from data in the few GeV/c region using an analysis based on a fixed-t analyticity in the form of fixed-t dispersion relations and FESR. Martin collaborated with Lea, R. G. Moorhouse and Oades in an energy-dependent multichannel analysis of KN data in the momentum range 0.44 - 1.19 GeV/c using parametrizations based on the K matrix. The amplitude and resonance parameters obtained for the S, P, D and F_5/2 waves were compared with those from other analyses.

M. K. Pidcock published two papers in 1974, the first with A. K. Common and D. Hodgkinson on 'The derivative of the p^op^o -> p^op^o g-wave' and the second on 'Crossing sum rules and the p^op^o -> p^op^o g-wave'.

General Physics Group

This group is listed under Massey's leadership in the 1964-65 Departmental Report. A short survey of the miscellaneous researches carried out during his headship of the department is followed by a review of his own and other work during that period in the fields of electron scattering, the resonating group method, and positron physics.

The first publication listed in the 1951-52 College Report is a paper by Bates and Massey on the negative ion concentration in the lower atmosphere. In Massey's work on negative ions and the upper atmosphere, it appeared in his 1937 paper that the removal of negative O ions by associative detachment in the E and F regions must be very slow. However a later examination with Bates, published in 1954, revealed a rapid mechanism, namely, that the O atom and the O^- ion approach along an attractive potential energy surface that intersects the final O₂ surface and within the crossing a radiationless transition leading to detachment can occur, the lifetime towards this transition possibly being so brief that detachment occurs in almost every collision.

Papers by Buckingham, with Dalgarno, covered the interaction of normal and metastable helium atoms, and the diffusion and excitation transfer of metastable helium in normal gaseous helium; one, with R. A. Scriven, was on diffusion in gaseous helium at low temperatures. Later work on metastable helium included the de-excitation of its atoms in helium (Burhop), its destruction by collision-induced radiation (Burhop & Marriott), and its conversion from the singlet to triplet state by electron collision (Marriott). Marriott and Seaton obtained a simple wave function for He 1s2s¹S.

Early work on the continuous absorption by the hydrogen molecular ion by Buckingham, with S. Reid and R. Spence, was followed by a consideration of (i) the detachment of electrons from the ion by impact with neutral atoms (D. W. Sida), (ii) its hyperfine structure (Dalgarno, T. N. L. Patterson & Somerville), and (iii) its continuous absorption coefficient (Somerville). Somerville also published papers on the importance of conservation conditions in distorted wave calculations, the correlation energies of the helium sequence, the effect of coupling to n=3 states on Born 1s-2s and 1s-2p e-H collision cross-section, and cross-sections for e-H collisions in the Born approximation to the reactance matrix.

The discussion of collision processes in meteor trails by Massey and Sida was followed by two papers from Sida, namely, atomic collisions in meteor trails, and the scattering of positive ions by neutral atoms. A consideration of symmetry effects in gas kinetics, in particular, the helium isotopes by Buckingham, with O. Halpern, was followed by molecules with almost spherical symmetry, with C. Carter. Carter carried out work on molecular orbital wave functions for methane and silane, and a theoretical study of pentavalent phosphorus. Earlier M. J. M. Bernal had obtained analytical wave functions for methane and the ammonium ion, and had written on metallic ammonium with Massey.

In connection with the experimental work on atomic hydrogen, quantal scattering theory was applied by Buckingham and Fox to calculate the coefficients of viscosity of the gas from 25 to 300K. Then E. Gal joined them in using a more realistic interaction potential to evaluate the coefficients of viscosity and thermal conductivity from 1 to 400K. Fox and Gal also evaluated the differential and total elastic cross-sections for the collision of unpolarized hydrogen atoms for energies of the relative motion up to 0.37eV; the effect of the identity of the atoms was also considered.

In their work on collisions between atomic systems in the thirties, Massey and Mohr obtained a simple, widely used, formula describing the scattering of atoms by atoms at thermal energies. Some thirty years later Massey with R. B. Bernstein, Dalgarno and Percival applied the formal theory of scattering to the problem of rotational excitation and elastic scattering of homonuclear diatomic molecules by atoms. Earlier K. Takayanagi had considered the rotational transition of the hydrogen molecule by collision.

G. Stephenson published papers on field theory, namely, 'Affine field structure of gravitation and electromagnetism', 'Dirac's electrodynamics and Einstein's unified field theory, some properties of non-symmetric unified field theories' and, with C. W. Kilminster, 'A unified field theory of gravitation' and 'An axiomatic criticism of unified field theories'. P. W. Higgs's consideration of 'Vacuum expectation values as sums over histories', and 'Four-dimensional isobaric spin formalism' was followed by J. G. Gilson on 'Dispersion relation for non-linear vacuum polarization effects'.

In 1952 A. H. de Borde collaborated with G. R. Burbidge on the mesonic Auger effect. Burhop's interest in the Auger effect dated back to his first experimental research work at Melbourne for his M.Sc. degree. His continued interest in the effect led to the publication of his Cambridge Monograph on 'The Auger Effect and Other Radiationless Transitions' in 1952. In 1958 he published a paper on 'The K Auger spectrum', with W. N. Asaad, which extended his work on the theory of the effect to great detail. Later Asaad published his paper on 'Relativistic K electron wave functions by the variational principle.' Burhop also wrote papers on the disintegration of the deuteron by neutron impact, with B. H. Bransden, and on the effect of nuclear size on bremsstrahlung and electron pair production, the former with S. J. Biel. The production of bremsstrahlung in electron-electron collisions, and the radiative corrections to the scattering of electrons and positrons by electrons were considered by M. L. G. Redhead.

Percival published papers on a variational principle for scattering phases; the effect of mutual distortion on phase shifts of a colliding system; the partial wave theory of e-H collisions; the excitation of 3p levels of OI; and waves in a conducting sheet situated in a strong magnetic field. Earlier G. H. A. Cole published a paper on the dynamics of a non-uniform electrically conducting fluid and wrote articles on magnetohydrodynamics and the kinetic theory of monatomic liquids.

In the fifties P. Swan published papers on the elastic scattering of neutrons by tritons at 14MeV; the elastic scattering of neutrons by tritons and of protons by ³He; the existence of a bound state of ⁴H; and the elastic scattering of electrons by the excited 2s and 3s states of atomic hydrogen. G. A. Erskine calculated the energy per ion pair for -particles in helium. Nuclear disintegrations caused by 50-125 MeV protons and the production of t-mesons were considered by P. E. Hodgson. Then in the early sixties L. F. Abou-Hadid and K. Higgins wrote on the equivalent two-body method for the hypertriton, the former following with a paper on the effect of hard-core and three-body forces on the L-nucleon interaction. E. Leader considered the optical model in p-nuclear scattering and, with A. C. Hearn, fixed-angle dispersion relations for nucleon Compton scattering.

Turning to the Massey post-1950 researches on electron scattering, the following survey is along the lines of that in the B.B.D. biographical memoir, namely, through the application of variational methods. With atomic hydrogen as the target, he and B. L. Moiseiwitsch thoroughly studied the effects of exchange and polarization on elastic scattering; with G. A. Erskine he calculated the cross-section for the excitation of the 2s state by means of the distorted wave method, making full allowance for exchange; and with S. Khashaba he did the corresponding, more complicated, calculations for the 2p state, obtaining the polarization of the impact radiation as given by the different approximations - Born, distorted wave, Born-Oppenheimer, and exchange-distorted wave. A similar programme was followed on helium, Moiseiwitsch, at Massey's suggestion, investigating elastic scattering, and then the two of them combining to calculate the cross-sections for the excitation of the 2¹S and 2³S terms, and for the excitation of the 2³P term. The 2³S calculations were the first to give a sharp resonance peak just above threshold. Massey's two pioneering calculations, the second with Mohr, on elastic scattering of electrons by molecular hydrogen in the early thirties were unsuccessful in the energy region below 100eV. However quite good agreement with experiment was achieved in the mid-fifties by exploiting the power of variational methods with R. O. Ridley.

Bates in the biographical memoir records Massey's feeling that his work with the resonating group method was rather underrated. This led him to invite Phil Burke, who was a member of the UCL research team involved, to contribute the perceptive account of Massey's work included in the memoir. Burke begins by explaining that the method, proposed in two 1937 papers by J. A. Wheeler, was based on the idea that nucleons in nuclei spend fractions of their time resonating between various substructures or groups and, after discussing the general theory, considered the scattering of neutrons by deuterons and the binding energy of the triton. In the forties and fifties the method was extensively and almost exclusively developed and applied by the Massey group to study the problem of scattering involving few nucleons. The first paper by Massey and Buckingham in 1941 studied the scattering of neutrons by deuterons; the problem was formulated for various types of nuclear forces, and the resultant integro-differential equation solved for s- and p-wave scattering with the help of Drs. L. J. Comrie and H. O. Hartley of the Scientific Computimg Service, the work being one of the first and certainly the most detailed attempt to identify the nature of nuclear forces from the scattering of light nuclei. In the early fifties the work on n-d scattering was extended by Massey, Buckingham and S. J. Hubbard and by Massey and de Borde by the inclusion of higher partial waves and calculations to higher energies. Later Burke and H. H. Robertson, at Massey's suggestion extended the calculation to a wider range of nuclear forces; Bransden, K. Smith and C. Tate included tensor forces in the theory; and Burke and F. A. Hass allowed for the polarization of the deuteron during the collision. Massey reviewed the status of the work on the nuclear three-body problem at an International Conference on Nuclear Forces and the Few-Nucleom Problem held at College from 8-11 July 1959.

During the fifties several other few-nucleon systems were studied by the resonating group method. These included n-a scattering, determination of the spin-orbit interaction (Massey, S. Hochberg, Robertson & L. H. Underhill) and contribution of tensor forces (A. Sugie, Hodgson & Robertson); elastic scattering of neutrons by tritons and ³He (Bransden, Robertson & Swan) and theory of neutron-triton scattering (Hochberg, D. J. Newman & Robertson); deuteron-triton scattering, two channel, five nucleon reactions with central forces (W. Lasker, Tate B, Pardoe & Burke); and the binding energy of ⁸Be and ¹²C and a-a scattering (S. J. Biel, A. C. Butcher & J. M. McNamee). Much of the work was done on the pilot ACE and DEUCE computers at the National Physical Laboratory, Teddington with the collaboration of Robertson, who had written a general programme to solve the integro-differential equations by a linear algebraic method. Massey arranged for most of his students to spend periods varying from a few days to several months working at NPL with Robertson, most of the early aforesaid calculations being completed in this way. In 1958-59 the method was reprogrammed for the Feranti Mercury Computer at the University Computer Unit where Buckingham had become Director. In view of the computational difficulties only light systems could be studied with restricted approximate nucleon-nucleon interactions, nearly always an effective central force being used to represent on average the exact interaction, which involved spin-orbit and tensor components. Nevertheless results were obtained in fairly general agreement with experiment.

In the sixties work continued with most emphasis on n-d scattering. At Massey's suggestion J. W. Humberston carried out a series of calculations, the first on elastic scattering using rather simple spin and iso-spin dependent potentials. Distortion of the target deuteron was ignored at first, but later an elaborate variational calculation was done using a very flexible trial function incorporating terms representing all possible forms of distortion, and the first fully converged results for n-d s-wave phase shifts and scattering lengths were obtained. Distortion was found to be very important in the doublet spin state, but the discrepancy between the theoretical and experimental results indicated that no purely central potential was compatible with the three-nucleon data. It was therefore necessary to use potentials with central, tensor and spin-orbit components. In 1965 the Hamada-Johnson potential was the most accurate such potential and it was used in an elaborate calculation of the binding energy of the triton. Again an essentially fully convergent result was obtained, but the result (-6.3MeV) differed from the experimental value (-8.5MeV). At first the discrepancy was regarded as evidence for the existence of three-body forces; however the results were found to depend rather sensitively on some of the parameters in the potential and it would have been necessary to determine these parameters to a higher precision to establish the existence of such forces. Colleagues involved with Humberston in the triton binding energy work were S. M. Hawkins, M. A. Hennell & J. B. Wallace. In addition to the aforesaid work with realistic nucleon-nucleon potentials, Humberston (with R. L. Hall & T. A. Osborn) investigated various features of the three-body system using rather simple model potentials.

Massey read a paper (Can. J. Phys. 60, 461-470) on 'Gaseous positronics - past, present, and future' at the International Conference on positron collisions in gases held at York University, Toronto in 1981. He recalled that 1981 was 50 years from the time midway between the first observations of positrons in cosmic radiation and their theoretical prediction. Being at Cambridge carrying out both experimental and theoretical research (Rutherford always insisted that the lab should be closed between 6 pm and 9 am), he remembered "hearing about Dirac's ideas of the vacuum populated by electrons occupying all the available free particle states of negative energy, and arousing much interest that same evening at a meeting of the Junior Physical Club by describing Dirac's latest wizardry". He had been fascinated with Dirac's wave equation from his M. Sc. days in Melbourne, recalling "being sharply reprimanded by the Senior Demonstrator when I overtly studied Dirac's paper in the Proceedings of the Royal Society (A) while supposedly demonstrating to a practical class." His first scientific paper to be published was a calculation of the effect of a nuclear magnetic moment on the scattering of fast electrons using the Dirac equation. His first paper on positrons was concerned with their collisions at relativistic energies, namely, the calculation of the rate of radiationless annihilation of positrons in collisions with atoms with Burhop. Then he contrasted the scattering of positrons at relativistic energies with that of electrons at the same energies. The beginning of the experimental study of slow positrons in gases at the time of his transfer to the Quain chair of physics led to his special interest in positron physics. As mentioned on p. 112 there followed the collaboration with Mohr in a preliminary survey of the collision processes of positrons and positronium in gases, that with Moussa on positronium formation in helium, Fraser's calculations on positronium collisions in hydrogen and helium, and the establishment of the experimental positron physics group. Massey recalled a meeting with Ramsauer in West Berlin, when the latter remarked how interesting it would be if experiments were carried out with slow positrons in gases as with electrons to obtain total cross-sections as a function of energy. Massey replied that since the static field of an atom is repulsive for positrons, there would be no Ramsauer effect. In the mid-sixties he carried out schematic calculations with I. H. Sloan, W. J. Cody, J. Lawson & K. Smith to see what sort of variation of cross-section with velocity might be expected for positrons when polarization was taken into account. The results showed that it would not be surprising to find Ramsauer effects in the scattering. He was particularly gratified that the first systematic measurements of total cross-sections for scattering by positrons were made in the department in the early seventies. In the early seventies he published two papers on the behaviour of positrons in molecular gases, the first with Lawson and S. Hara on the dependence of their annihilation rates in rare gases on the presence of molecules, and the second with Hara on their annihilation in Ar-CO mixtures.

By 1970 Humberston's work on n-d scattering was ending and he became interested in collision problems associated with slow positrons in gases, and was able to apply his experience to carry out elaborate variational calculations to the relatively simple problems of positron elastic scattering. As an introduction to the field, he carried out with J. B. G. Wallace a detailed study of positron scattering by hydrogen atoms which yielded the first accurate results for the positron annihilation rate and the angular correlation of the g-rays. The results proved particularly interesting in helping to explain some features of the electron-positron annihilation radiation coming from the direction of the galactic centre. There followed the more complicated problem of positron scattering by helium atoms, definitive values of elastic scattering phase shifts and annihilation parameters being obtained for several partial waves. The resulting cross-sections were in excellent agreement with the most accurate experimental values, and were used to resolve a discrepancy between various experimental results. The values of the scattering and annihilation parameters were used in a detailed study of the lifetime spectrum of positrons diffusing in helium gas, excellent agreement being obtained with the most accurate experimental spectra. R. I. Campeau collaborated with Humberston in some of the work.

Turning his attention to positronium formation in positron-atom collisions, he calculated the s- and p-wave contributions in hydrogen. By examining the variation of the results with respect to systematic improvements in the trial function it was established that the results were essentially fully converged. C. J. Brown then collaborated with him in the calculation of the d-wave contribution, the combined results being the most accurate then available. Finally mention is made of the collaboration of M. S. T. Watts with Humberston to investigate low-energy positron-lithium scattering in the energy region below the first excitation threshold so that only elastic scattering and positronium formation needed to be considered.

CUSC (Computers in the Undergraduate Science Curriculum)

In 1973 the government established a 5-year National Development programme in Computer Assisted Learning (CAL) charged with stimulating CAL at all levels of education. A small group of scientific staff from UCL, Chelsea College and University of Surrey involved in CAL submitted a proposal to the National Development Programme for a substantial development project to use interactive graphical displays; this was accepted, and CUSC started officially in January 1974. Later Queen Elizabeth College joined the collaboration.

The original UCL staff involved, Castillejo and McKenzie, were joined by Humberston in the Autumn of 1973 on his return from a sabbatical in USA. McKenzie developed a PDP 11/34 computer to aid learning and teaching; a set of conversational programmes was used in the first-year laboratory to enable students to introduce themselves to computer programming in BASIC. He then developed two teaching packages, Phasors and Multiphasors, and used them in his first-year course on Waves, Optics and Acoustics. In the first, the amplitudes of two waves and the phase difference between them are chosen by the student; at any time he may change the phase difference, observe the wave sum, the phasor diagrams of the separate waves or their sum, and a plot of Intensity against phase difference for the waves. In the second, the number of waves and the increment of phase difference between them are specified by the student; the screen displays the phasor diagram for any phase difference, and upon request, a plot of Intensity against phase difference.

Two teaching packages, namely Schrödinger Bound State and Positive Energy respectively, were developed by Humberston and used extensively in his second-year quantum mechanics course to illustrate various basic ideas in quantum mechanics. In the first the student defines the width and depth of a square well, the particle mass and energy, and the function parity, and then views the corresponding curve of the wave function. In the second the student defines the potential barrier width and height, the particle mass and energy, and then views the wave functions for the incident, reflected, and transmitted waves; the real and imaginary parts may be shown separately; the transmission coefficient is listed and the probability density may also be displayed.

McKenzie became Project Director of the CUSC project in 1974; he is joint Editor (with L.R.B. Elton of Surrey and R. Lewis of Chelsea) of 'Interactive Computer Graphics in Science Teaching', a book first published in 1978 by Ellis Horwood Ltd., Chichester. The book records the development of the 4-year project, covering technical matters of computers, graphical terminals etc., and lists some 40 teaching packages developed for physics, chemistry, and biology students.

Teaching

In Massey's first session the undergraduate courses continued to be:
Intermediate - E1 Mathematical Group and E2 Biological Group;
General Degree - First-year, G 1, and Second Year, G 2;
Ancillary - First-year, A 1, and Second-year, A 2;
Special Degree - First, Second and Third-year, S 1, S 2 and S 3.

Members of staff accompanying Massey into the department, immediately became involved in the teaching of some of these courses, as the following lecture programme shows:
E1(Mathematical) and E2 (Biological) - Burhop, Fox and Jennings.
G1 and A1 (combined) - Heat, Fox; Optics, Griffith; Electricity & Magnetism, Heyland; Properties of Matter, and Sound, Burhop; G1 - Thermodynamics, Fox; A1 - Kinetic Theory, Henderson.
G2 and A2 (combined) - Optics, Griffith; Electricity & Magnetism, Electronics, Heymann; Sound, Burhop; Modern physics, Jennings; Gravitation, Kinetic Theory, Henderson.
S1 - Heat & Thermodynamics, Wood; S1 - Electricity & Magnetism, Duncanson and Heyland; Properties of Matter, combined with G1 and A1.
S2 - Heat and Thermodynamics, combined with S1, Properties of Matter and Sound, R. C. Brown; Modern Physics, Gibbs and G. B. Brown.
S3 - course was completely revised, an alternative Part II option on Mathematical Physics being introduced. Massey gave three lectures per week on Modern Physics throughout the session to all students. Boyd, Dodd and Hasted each gave one lecture per week on Selected Topics in Experimental Physics to students taking the Experimental Physics option, and Buckingham, Castillejo and Seaton gave a corresponding series in Mathematical Physics to those taking the new option. The six-hour Part II practical examination involved plotting curves showing how the rate of exhaustion of air from a Winchester flask by a water pump depended upon the rate of flow of water through the pump and on the pressure in the flask. The corresponding theoretical problem paper consisted of two questions, both to be answered. The first tabulated the variation of internal energy of a symmetrical diatomic molecule with internuclear distance and required the position and depth of the minimum energy to be determined and thence the best values of the coefficients in an approximate representation of the internal energy. Given an approximate formula for the vibrational and rotational energy levels of the molecule, an estimate was required of (a) the percentage of molecules occupying those levels in a gas at 2000K; (b) the variation of molar specific heat of the gas between 1000K and 6000K, assuming the reduced mass of one molecule to be equal to one proton. In the second question the number of disintegrations occurring in a small sample of radioactive material over successive periods of one day were tabulated for ten days. On the basis of the process being suspected of involving two successive disintegrations, it was required to estimate the half-life of the parent substance and of the intermediate product.

Postgraduate courses were introduced, namely, Bates on 'Atomic Collisions'; Seaton on 'Atomic and Molecular Structure'; Burhop on 'Nuclear Physics'; Castillejo on 'Field Theories'; and Massey on 'Relativistic Quantum Mechanics and Field Theory'.

Wood gave the Optics course to the combined S1 and S2 classes in the 1951-52 session, retiring at the end of the session. His formal retirement at the end of the session led to a change in the S-lecture programme namely, Heat & Thermodynamics and Optics being spread over two sessions, Fox starting with Heat & Thermodynamics to S1 in the 1951-52 session and completing the course with S2 in the following session, as Jennings started the corresponding cycle with the new S1 class; R. C. Brown and Dodd gave the corresponding Optics cycles starting with the S1 classes in the 1952-53 and 1953-54 sessions respectively. R. C. Brown's place in the Properties of Matter cycle with Henderson was taken over by G. B. Brown, Boyd replacing the latter with Gibbs on the S2 Modern Physics course; and Duncanson (then Burhop) and Heyland continued with the Electricity & Magnetism cycle.

A S1 problem class was introduced in the 1951-52 session being taken by Fox and Jennings, and the S2 Ancillary Mathematics course was taken over by Seaton in the 1952-53. As mentioned on p.52 Wood continued lecturing after his retirement, taking the three mid-day Intermediate lectures until the course was disbanded at the end of the 1956-57 session. The General degree course was also disbanded at the end of this session, leaving the department with one-year Ancillary courses for Biochemistry, Physiology, and Statistics students, and two-year Ancillary courses for Astronomy, Chemistry and Geology students.

As mentioned on p. 63 the department rather reluctantly introduced the College-based-course degree structure in 1966. (Earlier Massey had written to Gibbs expressing his alarm at which the proposals for the new degree structure were being rushed through and asked for this to be raised at the Board of Studies in Physics with the view to presentation at higher level in the University.) To appreciate the structure of the course units and syllabuses adopted, the following reference is made to the pre-1966 scheme, i.e., the University B. Sc. special degree in physics. To qualify for this degree, an undergraduate had to satisfy the examiners in (i) the ancillary examination in mathematics, normally taken at the end of the first year; (ii) the examination in mathematical methods in physics, normally taken at the beginning of the third term of the second year; (ii) part I of the final examination in physics, normally taken at the end of the second year; (iv) part II of the final examination, normally taken at the end of the third year. A new syllabus for part I came into operation in 1963, the main headings of of the five papers being as follows:
Paper I - Newtonian Mechanics; Special Relativity; Continuous Media: Vibrations and Waves in Mechanical Systems; Kinetic Theory.
Paper II - Heat and Thermodynamics: Structure of Matter; Irreversible Processes.
Paper III - Fields; Circuits and Techniques; Magnetism; Electrons in Solids; Conduction of Gases.
Paper IV - General Properties of Waves; Electromagnetic Radiation; Electromagnetic Spectrum; Interference; Diffraction; Interaction with Matter; Geometric Optics.
Paper V - Elementary Particles; Atomic Physics; Nuclear Physics.
These theory papers were set and marked by appropriate committees of the University Board of Examiners in Physics.

From 1965 only one six-hour examination in practical physics was held in Part I, this involving at UCL a common experiment of the problem type; the examination involving an experiment of the routine type being abolished, more weight was given to the normal laboratory course work in experimental physics.

For the Schools of the University Part II was an internal examination and at UCL three theory papers were set and marked by UCL staff. There were experimental and mathematical physics options. The common syllabus consisted of quantum mechanics, atomic physics, nuclear physics, elementary particle physics, statistical mechanics, solid state physics, and some special topics such as superfluidity and superconductivity. Students taking the experimental option had additional lectures on statistical methods and advanced electronics; they attended courses in Engineering Drawing, Workshop Practice and Experimental Radioactivity; and they undertook a major experimental project and presented a report thereon. Students taking the mathematical physics option attended a course of lectures on classical mechanics, electrodynamics, advanced mathematical methods, numerical analysis and computing; and each student was allotted a problem in Mathematical Physics of the research type and presented a dissertation on it.

Courses introduced in place of previous Ancillary courses were:
B101 Basic Physics for Biological sciences (1 c.u.)
B102 Basic Physics for Chemistry (1 c.u.).
B104 Physics for Astronomy (1 c.u.).
B201 Physics for Biological sciences (¹/₂ c.u.).
B202 Electricity and Magnetism (¹/₂ c.u.).
B203 Physical Measurements (¹/₂ c.u.).
B204 Physics for Astronomy (1 c.u.).

University regulations required that during the three-year course a student must complete a minimum of 9 course units and pass the examinations associated with at least 8 of them in order to obtain a degree.

As explained below, first-year physics students started in the 1966-67 session the following 11 course-units scheme, second and third-year students carrying on with the lectures under the B.Sc. special degree system.

First Year	Second Year	Third Year
B11 General Physics	B21 Bulk Properties of Matter II	C31 Theoretical Physics
B12 Bulk Properties of Matter I	B22 Light & Electro-magnetism II	C32 Solid State Physics
B13 Light & Electro-magnetism I	B23 Atomic & Nuclear Physics	C33 Atomic, Nuclear & High Energy Physics
B1 Pure & Applied Mathematics	B4 Mathematical Methods in Physics

The nine Physics courses were approved by the Board of Studies in Physics, the two Mathematics courses by the Board of Studies in Mathematics.

The main headings of the physics courses were:
B11 - Historical Introduction and Survey of Modern Physics; Vibrations and Waves; Classical Mechanics; Special Theory of Relativity.
B12 - Heat and Thermodynamics; Introductory Statistical Mechanics; Kinetic Theory of Gases.
B13 - Geometrical Optics; Interference; Diffraction; Polarization; Electrostatics; Steady Currents; Magnetic Effects of Currents; A. C. Circuit Theory; Electromechanical Devices.
B21 - Mechanics; Relativity; Sound and Ultrasonics; Geophysics; Thermodynamics.
B22 - Light; Electricity and Magnetism; Electromagnetic Waves; Electronics.
B23 - Quantum Theory; Atomic Physics; Nuclear Physics; Solid State Physics.
C31 - Mathematics; Quantum Mechanics; Astrophysics.
C32 - Statistical Mechanics; Solid State and Metal Physics; Superfluidity and Superconductivity; Electronics.
C33 - Atomic Physics; Nuclear Physics; b-radioactivity; Elementary Particle Physics.

The Physics Sub-Board of Examiners in Physics was required to submit a scheme for the award of Honours to the College Board for approval on the basis of relative weights of 1:2:3 for first, second, and third-year work. It decided that B1 and B4 should count equally with the three first and three second-year physics courses respectively; that it would work on the basis of percentage marks rather than on grades 1-9, favoured by the Biological Science departments which operated a common scheme for honours, namely, grades 1-9, divided into groups of three, classed A, B, and C respectively. To comply with Faculty requirements it established an equivalent percentage mark-grade band corresponding to the classifications A, B, C, and F given to students for course-unit examinations. The scheme for the award of Honours was based on that used for the B.Sc. special degree.

In September 1968 a new third-year course C30 on Physics of Solids was introduced to form the ninth course-unit for six students who had failed two or more B course-units, they forming a class equivalent to the old B. Sc. pass degree class.

The new course structure was devised and the individual course units planned on the basis of the general principles (i) the course should continue to be of a special nature, directed towards the dedicated student of physics who aimed to become a professional physicist, (ii) emphasis should be on those branches of the subject necessary for an appreciation of the main points of growth of contemporary physics, (iii) since the requisite background knowledge of basic physics was sufficiently comprehensive and detailed to constitute a full three years' study, leaving no time for optional courses, a common course structure should be followed by all undergraduates, (iv) the separate course units should be designed to reveal the unity of the subject and where possible to allow an increasing depth of treatment to be followed year by year. Hence the third-year experimental and mathematical physics of the B.Sc. degree were abolished and a common lecture course was adopted with the recognition that a special aptitude for mathematical physics or a particular inability in experimental physics could be met in the choice of the third-year project.

A syllabus revision committee was appointed, consisting of Massey, Burhop, Castillejo, Heymann, Seaton and Fox, to devise a coherent course unit system within the foregoing framework. It sought not only the views of departmental staff, but also those of other physics departments, e.g., a newly, and an old, established department, Sussex and Manchester respectively. In arranging the first-year course units, the needs of 'freshers' were particularly borne in mind, B11 being designed to encourage and stimulate enthusiasm for physics at university level, particular care being paid to its teaching, even though parts of B12 and B13 might appear less interesting. Prof. Massey instituted regular meetings with students to obtain first-hand information of their experiences of the new courses and in 1967 a staff meeting was held to review the year's experience.

In parallel with the syllabus committee, a sub-committee was appointed, consisting of Fox, Heyland, Bullock, Lush, M. J. B. Duff and Metheringham, to consider the experimental programme. In the B.Sc. special degree course, first and second-year students spent three afternoons per week in the laboratories and wrote accounts of each experiment performed, handing in a practical note-book for marking each week. It was decided to abolish the old Part I practical examination and to introduce complete continuous assessment represented by a course mark assigned to each Physics course-unit studied. Students were required to spend only two afternoons per week in the laboratories during their first and second years and present detailed accounts of only about six experiments performed, half of which were chosen by themselves. The first and second-year experiments were designed to illustrate physical principles and theories, to teach specific techniques, and to provide an integrated training in the essentials of experimental physics. Some experiments were open-ended and some were project-typed, designed to give scope for creativity in the context of experimental physics. Some specialised short courses were retained, e.g. workshop practice, technical drawing and radioactivity, and new courses in electronics and computing were introduced. The third-year major project was retained since this offered greatest scope for initiative and creativity, and had proved to be highly successful in stimulating interest and developing critical thought and attitudes; again credit for the project was allocated to each C course-unit.

A new third-year scheme was introduced for the 1969-70 session, under which there were two common courses and one optional course, the latter reflecting student opinion. The common courses were:
C34 - Quantum Mechanics, Atomic Physics, Solid State Physics.
C35 - Nuclear Physics, Elementary Particle Physics, Mathematics.

The optional course was chosen from:
C36 - Astrophysics and Geophysics.
C37 - Plasma Physics, Materials Science, Superfluidity and Superconductivity.

As mentioned on p. 68, the swing away from the physical sciences among candidates seeking admission to the universities hit the department badly in physics, and led to the introduction of two new degree courses. Following discussions with several members of the Departments of Chemistry and Physics with Professors Nyholm and Massey a working party, consisting of Professors Millen and Tobe with Professor Willmore and B. G. Duff, explored the possibility of chemistry/physics or other interdisciplinary degree courses. Consequently a new joint Chemistry/Physics degree course, intended for a small number of high-grade students and offering the choice of transfer to chemistry or physics at the end of the first year, was introduced in the 1969-70 session, with the admission of 8 students.. This required the introduction of two new half course-units of physics, namely, B13(a) - Electromagnetism and B205 - Solid State Physics, specifically for the joint-degree students. The degree structure was:

First Year	Second Year	Third Year
B1, B11, B13(a), and  11/2 c.u. of Chemistry	B4, B23, B205 and  11/2 c.u. of Chemistry	3 c.u. and a project, subject to a  minimum of 1 c.u. of Phys/Chem.

An Applied Physics Committee, consisting of Willmore, D. G. Davis, M. J. B. Duff and M. J. Esten explored the possibility of an applied physics degree course, with the result of the admission in the 1970-71 session of 7 students to the newly instituted Applied Physics degree course. Only two additional third-year course-units were introduced, namely, C38 - Systems, Computers and Control, and C39 - Microwaves and Modern Optics, a joint c.u. with the Department of Electronic and Electrical Engineering. The degree structure only differed from that for the Physics degree in the third year, namely:

First Year

	Second Year	Third Year
B11 General Physics	B21 Bulk Properties of Matter II	C31 Theoretical Physics
B12 Bulk Properties of Matter I	B22 Light & Electro-magnetism II	C32 Solid State Physics
B13 Light & Electro-magnetism I	B23 Atomic & Nuclear Physics	C33 Atomic, Nuclear & High Energy Physics
B1 Pure & Applied Mathematics	B4 Mathematical Methods in Physics

The nine Physics courses were approved by the Board of Studies in Physics, the two Mathematics courses by the Board of Studies in Mathematics.

The main headings of the physics courses were:
B11 - Historical Introduction and Survey of Modern Physics; Vibrations and Waves; Classical Mechanics; Special Theory of Relativity.
B12 - Heat and Thermodynamics; Introductory Statistical Mechanics; Kinetic Theory of Gases.
B13 - Geometrical Optics; Interference; Diffraction; Polarization; Electrostatics; Steady Currents; Magnetic Effects of Currents; A. C. Circuit Theory; Electromechanical Devices.
B21 - Mechanics; Relativity; Sound and Ultrasonics; Geophysics; Thermodynamics.
B22 - Light; Electricity and Magnetism; Electromagnetic Waves; Electronics.
B23 - Quantum Theory; Atomic Physics; Nuclear Physics; Solid State Physics.
C31 - Mathematics; Quantum Mechanics; Astrophysics.
C32 - Statistical Mechanics; Solid State and Metal Physics; Superfluidity and Superconductivity; Electronics.
C33 - Atomic Physics; Nuclear Physics; b-radioactivity; Elementary Particle Physics.

The Physics Sub-Board of Examiners in Physics was required to submit a scheme for the award of Honours to the College Board for approval on the basis of relative weights of 1:2:3 for first, second, and third-year work. It decided that B1 and B4 should count equally with the three first and three second-year physics courses respectively; that it would work on the basis of percentage marks rather than on grades 1-9, favoured by the Biological Science departments which operated a common scheme for honours, namely, grades 1-9, divided into groups of three, classed A, B, and C respectively. To comply with Faculty requirements it established an equivalent percentage mark-grade band corresponding to the classifications A, B, C, and F given to students for course-unit examinations. The scheme for the award of Honours was based on that used for the B.Sc. special degree.

In September 1968 a new third-year course C30 on Physics of Solids was introduced to form the ninth course-unit for six students who had failed two or more B course-units, they forming a class equivalent to the old B. Sc. pass degree class.

The new course structure was devised and the individual course units planned on the basis of the general principles (i) the course should continue to be of a special nature, directed towards the dedicated student of physics who aimed to become a professional physicist, (ii) emphasis should be on those branches of the subject necessary for an appreciation of the main points of growth of contemporary physics, (iii) since the requisite background knowledge of basic physics was sufficiently comprehensive and detailed to constitute a full three years' study, leaving no time for optional courses, a common course structure should be followed by all undergraduates, (iv) the separate course units should be designed to reveal the unity of the subject and where possible to allow an increasing depth of treatment to be followed year by year. Hence the third-year experimental and mathematical physics of the B.Sc. degree were abolished and a common lecture course was adopted with the recognition that a special aptitude for mathematical physics or a particular inability in experimental physics could be met in the choice of the third-year project.

A syllabus revision committee was appointed, consisting of Massey, Burhop, Castillejo, Heymann, Seaton and Fox, to devise a coherent course unit system within the foregoing framework. It sought not only the views of departmental staff, but also those of other physics departments, e.g., a newly, and an old, established department, Sussex and Manchester respectively. In arranging the first-year course units, the needs of 'freshers' were particularly borne in mind, B11 being designed to encourage and stimulate enthusiasm for physics at university level, particular care being paid to its teaching, even though parts of B12 and B13 might appear less interesting. Prof. Massey instituted regular meetings with students to obtain first-hand information of their experiences of the new courses and in 1967 a staff meeting was held to review the year's experience.

In parallel with the syllabus committee, a sub-committee was appointed, consisting of Fox, Heyland, Bullock, Lush, M. J. B. Duff and Metheringham, to consider the experimental programme. In the B.Sc. special degree course, first and second-year students spent three afternoons per week in the laboratories and wrote accounts of each experiment performed, handing in a practical note-book for marking each week. It was decided to abolish the old Part I practical examination and to introduce complete continuous assessment represented by a course mark assigned to each Physics course-unit studied. Students were required to spend only two afternoons per week in the laboratories during their first and second years and present detailed accounts of only about six experiments performed, half of which were chosen by themselves. The first and second-year experiments were designed to illustrate physical principles and theories, to teach specific techniques, and to provide an integrated training in the essentials of experimental physics. Some experiments were open-ended and some were project-typed, designed to give scope for creativity in the context of experimental physics. Some specialised short courses were retained, e.g. workshop practice, technical drawing and radioactivity, and new courses in electronics and computing were introduced. The third-year major project was retained since this offered greatest scope for initiative and creativity, and had proved to be highly successful in stimulating interest and developing critical thought and attitudes; again credit for the project was allocated to each C course-unit.

A new third-year scheme was introduced for the 1969-70 session, under which there were two common courses and one optional course, the latter reflecting student opinion. The common courses were:
C34 - Quantum Mechanics, Atomic Physics, Solid State Physics.
C35 - Nuclear Physics, Elementary Particle Physics, Mathematics.

The optional course was chosen from:
C36 - Astrophysics and Geophysics.
C37 - Plasma Physics, Materials Science, Superfluidity and Superconductivity.

As mentioned on p. 68, the swing away from the physical sciences among candidates seeking admission to the universities hit the department badly in physics, and led to the introduction of two new degree courses. Following discussions with several members of the Departments of Chemistry and Physics with Professors Nyholm and Massey a working party, consisting of Professors Millen and Tobe with Professor Willmore and B. G. Duff, explored the possibility of chemistry/physics or other interdisciplinary degree courses. Consequently a new joint Chemistry/Physics degree course, intended for a small number of high-grade students and offering the choice of transfer to chemistry or physics at the end of the first year, was introduced in the 1969-70 session, with the admission of 8 students.. This required the introduction of two new half course-units of physics, namely, B13(a) - Electromagnetism and B205 - Solid State Physics, specifically for the joint-degree students. The degree structure was:

First Year	Second Year	Third Year
B1, B11, B13(a), and  11/2 c.u. of Chemistry	B4, B23, B205 and  11/2 c.u. of Chemistry	3 c.u. and a project, subject to a  minimum of 1 c.u. of Phys/Chem.

An Applied Physics Committee, consisting of Willmore, D. G. Davis, M. J. B. Duff and M. J. Esten explored the possibility of an applied physics degree course, with the result of the admission in the 1970-71 session of 7 students to the newly instituted Applied Physics degree course. Only two additional third-year course-units were introduced, namely, C38 - Systems, Computers and Control, and C39 - Microwaves and Modern Optics, a joint c.u. with the Department of Electronic and Electrical Engineering. The degree structure only differed from that for the Physics degree in the third year, namely:

First Year	Second Year	Third Year
B1, B11, B12, B13	B4, B21, B22, B23	C38, C39 and 1 c.u.  from the other four

A change in the Physics degree structure was made in the third-year courses, namely, C34, C35 and 1 c.u. chosen from C36, C37, C38 and C39.

The B.Sc. (Special) degree in Astronomy included observational and practical work carried out at the Observatory at Mill Hill. In addition to Astronomy, the course included a one-year ancillary course in Mathematics and a two-year ancillary course in Physics. The examinations in ancillary Mathematics and ancillary Physics were taken at the ends of the first and second sessions respectively. Part I of the final examination in Astronomy was taken normally at the end of the second session, and Part II at the end of the third session. Students were required to pass the normal test on the translation into English of scientific texts in two languages. Astronomy lectures were given, e.g., as follows:

First Year - S1 (Part 1)
S1-1 Descriptive astronomy: Monday at 10; Wednesday at 12.
S1-2 Spherical astronomy: Wednesday at 10; Friday at 12.
S1-3e Observational astronomy; Thursday at 6.

Second Year - S2 (Part 1)
S2-1 Astrophysics, (50 lectures).
S2-2 Dynamics.
S2-3 Spherical astronomy, (20 lectures).

Third Year - S3 (Part 2)
Three courses, of 40 lectures each, selected by arrangement from:

Stellar structure	Galactic structure
Astronomical spectroscopy	Radio astronomy
Stellar atmospheres	Solar physics
Celestial mechanics	Mathematical astrophysics
Statistical astronomy

The Observatory was open for practical work on Tuesday and Thursday from 2 to 10 p.m. First-year students attended practical classes on Thursdays, and second and third-year students attended on Tuesdays and Thursdays.

The Astronomy Department courses listed for the new B. Sc. degree were:

B1 Astronomy (1¹/₂ c.u.)
B2 Astrophysics (1¹/₂ c.u.)
B3 Orbital astronomy (¹/₂ c.u.)
B4 Stellar astronomy (¹/₂ c.u.)
C1 Observational astronomy (1 c.u.)
C2 Stellar interiors and atmospheres (1 c.u.)
C3 Solar and radio astronomy (1 c.u.)
C4 Stellar and galactic systems (1 c.u.)
C5 Statistical astronomy (¹/₂ c.u.)
C6 Lunar and planetary astronomy (¹/₂ c.u.)
These courses were approved by the University Special Advisory Committee in Astronomy.

The 1974-75 session was historic for several reasons, the most significant being it was the last of the Massey regime. The first entry to a joint Astronomy-Physics B.Sc. degree and the introduction of half-course units took place in October 1974. Massey started his last series of lectures, giving the ¹/₂ c.u. on Modern Physics and Astronomy to the Physics, Astronomy and joint Astronomy and Physics students, and Wilson started his first series, giving the ¹/₂ c.u. on Foundations of Modern Astronomy to the Astronomy and joint Astronomy and Physics students. As reported on p. 70, the flexibility of the half-units reducing the work-load of some students and enabling the less able student to select less demanding courses, but not retarding the most able, produced an immediate reduction in the drop-out rate of the first-year students. These half-units arose from a comprehensive review of the existing courses by a syllabus re-organization committee, proposed courses being examined by small groups of teachers suggesting tentative lists of topics to be included each course; the committee then ensured the coherence of topics in each course. The applied physics third-year courses resulted from the committee's discussions with the Department of Electronic and Electrical Engineering. A half-unit course normally consisted of c. 35 lectures and c. 5 separately time-tabled discussion periods, the latter enabling revision of difficult topics, attention to specific problems that had arisen, and generally to monitor the progress of the course.

The structures of the five degree courses offered by the department were listed in the 1974 departmental booklet as follows:

Physics and Applied Physics Degree Courses

First Year
1 c.u. Practical physics, including courses in workshop practice, engineering design and drawing, statistics, and computer programming in FORTRAN language.
¹/₂ c.u. Electricity and magnetism.
¹/₂ c.u. Modern physics and astronomy.
¹/₂ c.u. Thermodynamics, kinetic theory and radiation.
¹/₂ c.u. Waves, optics and acoustics.
¹/₂ c.u. Mathematics in physics.
¹/₂ c.u. Pure mathematics or Supplementary mathematics.

Second Year
1 c.u. Practical physics, including lectures on electronics with associated laboratory work.
¹/₂ c.u. Electromagnetic theory.
¹/₂ c.u. Quantum physics.
¹/₂ c.u. Mathematical methods in physics I. PLUS
Three half-unit courses chosen from the options:
Atomic and nuclear physics.
Earth resources.
Mathematical methods in physics II.
Modern acoustics and fluid mechanics (recommended for Applied Physics students).
Physics of solids and statistical mechanics.

Third Year
1 c.u. Project
PLUS
Six optional half-unit courses chosen from:
Physics students chose the majority of their options from the Physics list including;
Atomic and molecular physics; Extreme states of matter; Methods of mathematical physics; Nuclear
and particle physics; Plasma physics; Quantum theory; Solid state physics.

Applied Physics students chose the majority of their options from a list including;
Computer hardware; Computer software and systems; Control theory and machine intelligence;
Microwaves; Modern optics; Project management.

Both Physics and Applied Physics students could also choose options from the Astronomy list.

Astronomy Degree Course

First Year
¹/₂ c.u. Practical physics, including courses in workshop practice, engineering design and drawing, statics and computer programming in FORTRAN language.
¹/₂ c.u. Practical astronomy.
¹/₂ c.u. Basic astronomy.
¹/₂ c.u. Modern physics and astronomy.
.¹/₂ c.u. Physics.
¹/₂ c.u. Mathematical astronomy.
¹/₂ c.u. Mathematics for physics.
¹/₂ c.u. Pure mathematics or Supplementary mathematics. Second Year
1 c.u. Practical astrophysics, including lectures on electronics with associated laboratory work.
¹/₂ c.u. Astronomical techniques.
¹/₂ c.u. Astrophysics and atomic physics.
¹/₂ c.u. Astrophysics and radiation.
¹/₂ c.u. Astrophysics and properties of gases.
PLUS
Two half-unit courses chosen from the options;
Mathematical methods in physics I; Mathematical methods in physics II; Earth resources or another physics option; Introduction to geology.

Third Year
1 c.u. Project.
¹/₂ c.u. Observational astronomy.
PLUS
Five optional half-unit courses chosen from the Astronomy list:
Cosmic abundances of the elements; Extra-galactic astronomy; Geophysics; High-energy astrophysics; Interstellar physics; Lunar geology; Planetary astronomy; Solar physics; Stellar atmospheres; Stellar structure and evolution; Relativity and cosmology.
Options could also be chosen from the Physics or Applied Physics list.

Astronomy and Physics Degree Course

First Year
¹/₂ c.u. Practical physics, including courses in workshop practice, engineering design and drawing, statistics and computer programming in FORTRAN language.
¹/₂ c.u. Basic astronomy.
¹/₂ c.u. Modern physics and astronomy.
¹/₂ c.u. Electricity and magnetism.
¹/₂ c.u. Waves, optics and acoustics.
¹/₂ c.u. Mathematics for physics.
¹/₂ c.u. Practical astronomy or practical physics.
¹/₂ c.u. Pure mathematics or Supplementary mathematics. Second Year
1 c.u. Practical astrophysics, including lectures on electronics with associated laboratory work.
¹/₂ c.u. Astrophysics and atomic physics.
¹/₂ c.u. Astrophysics and radiation.
¹/₂ c.u. Astrophysics and properties of gases.
¹/₂ c.u. Quantum and solid state physics.
¹/₂ c.u. Mathematical methods in physics I.
PLUS
One half-unit course chosen from:
Astronomical techniques; Earth resources; Mathematical methods in physics II; Modern acoustics and fluid dynamics.

Third Year
1 c.u. Project.
PLUS
Six half-unit courses chosen from the three third-year lists of options subject to a minimum of two in
Astronomy and two in Physics or Applied Physics.

Chemistry and Physics Degree Course

First Year
¹/₂ c.u. Chemistry of atoms and molecules.
¹/₂ c.u. Physical chemistry, including practical work.
¹/₂ c.u. Chemical physics.
¹/₂ c.u. Practical physics, including courses in engineering design and drawing, statistics, and computer programming in FORTRAN language.
¹/₂ c.u. Electricity and magnetism.
¹/₂ c.u. Waves, optics and acoustics.
¹/₂ c.u. Mathematics for physics.
PLUS
¹/₂ c.u. Pure mathematics or Supplementary mathematics Second Year
1 c.u. Physical Chemistry.
¹/₂ c.u. Practical physics, including lectures on electronics with associated laboratory work.
¹/₂ c.u. Atomic and nuclear physics.
¹/₂ c.u. Electromagnetic theory.
¹/₂ c.u. Chemical physics.
¹/₂ c.u. Mathematical methods in physics.
PLUS
¹/₂ c.u. Pure mathematics or any other available Chemistry or Physics option.

Third Year
1 c.u. Project in Chemistry or Physics.
PLUS
Six half-unit courses chosen from any of the third-year options offered by the two Departments, subject to a minimum of two in Chemistry and two in Physics or Applied Physics.

It was possible to transfer from a joint honours course to one of the associated single subject courses at the end of the first year, without loss of time or credit; a similar transfer from Physics to Applied Physics or vice versa could be made at the end of the first or second year.

The statistics component of the first-year practical physics course embraced the statistical analysis of experimental data and FORTRAN programming using the College IBM 360/65 computer. In the first year, Physics students started project work in the summer term, e.g., construction of magnetometers of the type used in spacecraft. A more extensive six-weeks project was undertaken in the second year, e.g., Schlieren photography in a wind tunnel. The Physics third-year major project could be be experimental or theoretical, a wide range of topics being available e.g., development of x-ray, ultra-violet and infra-red detectors, study of traffic control problems by computer techniques, investigations using molecular and positron beams, analysis of winds on Mars, and a theoretical study of pulsars. Besides the third-year project, the Astronomy students had an advanced course in observational astronomy, the main telescopes used by them at the Observatory being the 24-inch Radcliffe refractor and a modern 24-inch reflector.

In the 1975-76 session lectures for first and second-year students changed from the term to the semester system then introduced in the Faculty of Science.

Tutors

Some academic tutorials were introduced in the 1954-55 session, a systematic system following later with all students attending a weekly tutorial for one hour. Pairs of first and second-year students were tutored by a member of the teaching staff and on alternate weeks took their "problem" books, which had been marked by their tutor, for discussion of any outstanding points; later these students met in groups of four. Third-year students met in groups of two, with specially chosen postgraduate students as tutors. The introduction of the course-unit degree system led to a cyclic arrangement of tutorials for first-year students, namely, four sets of students, each consisting of three sub-sets, the twelve sub-sets moving cyclically each week amongst the three tutors assigned to each set; however this was abandoned in 1969. Third-year optional course-units led to a weekly cyclical movements of tutorial sub-sets amongst tutors assigned to specific course-units.

A Departmental Tutor was not appointed until 1964, when Dodd took on the post. Duties of departmental tutors, as approved by the College Committee on 6 July 1965 and amended in the light of subsequent developments, were classified as Academic and Pastoral, the former consisting of Admissions, Progress and Attendance, Vacation Study, Examinations, Scholarships, Advice on Courses, and Departmental Leaflets, and the latter into References, Student Problems and Social Affairs. Before 1964 Wood and then Gibbs had served in that capacity with the Science Faculty Tutorship. When Dodd succeeded Gibbs as Faculty Tutor in the following session in 1965, Fox joined him as Departmental Tutor, assuming full responsibility of the post in 1966 when Dodd became increasingly involved with the introduction of the B. Sc. course-unit system. The procedure of admission of students began early in the first term with the arrival of the UCCA forms completed by applicants for admission to the department; following Dodd's procedure, these were scrutinized by Fox, who selected a list of candidates for interviews and carried them out in his room on the top floor. Typically an interview lasted about twenty minutes, beginning with questions about the interests and activities of the candidate, including any special references on the application form, then proceeding to ascertain the candidate's suitability for the selected course, and ending with the performance of some mathematical problems during my perusal of the practical physics notebook, which each candidate brought to the interview. In the early days a very good candidate, whose first preference was UCL, was given an AL 'pass-level' offer which had to be accepted or rejected; the standard offer was a grade C in both physics and mathematics; however a the offer for the combined Chemistry/Physics course was a grade B in physics, mathematics and chemistry. The interview being over, the candidate was taken downstairs, on a short tour of the three undergraduate laboratories. The progress of students in each of the three years was regularly reviewed at interviews during the first and second terms, and references written usually for third-year students.

In 1970 Imrie and Miller became Assistant Tutors, taking over student admissions to the department; and in 1974, when Fox became the College Schools Liaison Officer, McKenzie joined him as Tutor taking over responsibility for students, starting with that year's intake. McNally was appointed Departmental Tutor in Astronomy in 1965, Somerville succeeding him in 1970.

Teaching Administration

Gibbs became Superintendent and then Deputy Director of the Undergraduate Laboratories on Wood's retirement. After the occupation of the New Wing with the three undergraduate laboratories, Fox, R. C. Brown and effectively Heyland took charge of the first, second, and third-year laboratories under the general control of Gibbs. When Gibbs retired, the title of Deputy Director was abolished, Lush replaced Fox, Bullock replaced Brown, and Heyland became responsible for laboratory organization and student affairs for the foregoing laboratories under the leadership of Fox as head of the undergraduate teaching group. Two members of the academic staff and two postgraduate students were assigned to each of the first and second-year laboratories during each afternoon session, Heyland and project supervisors attending the third-year laboratory. Demonstrating, lecturing (including timetabling), tutoring and examinations were organized by Fox, later D. H. Davis taking over examinations; and Metheringham took charge of theatre demonstrations.

Professors' Meetings

In late September 1968 Prof. Massey suggested that informal and regular meetings of the departmental professors should take place to discuss the existing problems of the department and ideas for future development. Eight dates were fixed for these meetings during the session, starting with Friday, 18 October at 2.30 pm, followed by seven on Tuesdays at 3.00 pm between 5 November and 3 June. All of the meetings were on Tuesdays, except the first for which it was impossible to find a suitable Tuesday; Tuesdays were chosen to fit in with Professorial Board Meetings at 4.30 pm. In addition to the professors, Drs. D. G. Davis and Fox attended the meetings. At the first meeting Prof. Massey reported some proposed movements of research groups involving the Rocket, Infra-red, and Gargamelle groups. A general discussion of topics for consideration at future meetings resulted in the following:

(1) allocation of departmental resources;
(2) implications of three reports, two from the Committee on Manpower Resources for Science and Technology and one from the Council for Scientific Policy, namely:
'The Brain Drain; report of a Working Group on Migration', chaired by F. E. Jones, Managing Director of Mullard Ltd.;
'The Flow into Employment of Scientists, Engineers and Technologists', chaired Edinburgh University;
'Enquiry into the Flow of Candidates in Science and Technology into Higher Education, chaired by F. S. Dainton, V-C of Nottingham;
(3) the proposed Applied Physics course;
(4) the syllabus and effectiveness of the postgraduate courses;
(5) the grading of dissertations and the weighting in the final examination.

It was decided that the agenda of future meetings should be circulated with minutes of the previous meeting mainly reporting decisions taken; L. Castillejo would be the convenor and D. G. Davis, the secretary.

Topics for subsequent meetings included e. g., departmental grants, allocation to groups, academic and technical staff, academic staff meetings; staff-student relations, consultative committee and its library sub-committe; undergraduate teaching - introduction of new degree courses, syllabuses (arising from the implementation of the report of the Committee on Academic Organisation, chaired by Owen Saunders, Boards of Study function of approval of syllabuses was delegated to Schools without any formal requirement for involvement of staff other than the head of department), course-unit examinations, second marking of papers, assessment for honours, tutorials; intake of student, undergraduate and postgraduate; quinquennial development; future of astronomy in university, etc.

As an illustration of the financial allocation to the departmental groups, the following summary of their expenditure in the 1967-68 session, amounting to £364,538, is given:

Undergraduate Teaching
Laboratories; Theatres; Development	£13,682
Theoretical Research
Atomic Physics and Astrophysics	1,298
General Physics	704
High Energy Physics	952
Experimental Physics
High Energy:-
Bubble Chamber & Emulsion	26,534
Spark chamber	7,912
Atomic & Molecular:-
Ionic & Electronic	13,594
Atomic Physics	33,422
Molecular Beams	18,549
Other Experimental Physics	4
Space Science & Astronomy:-
Mullard Space Science Laboratory	148,170
Infra-red Balloon	9,266
Space Science & Atmospheric Structure	32,494
Service Groups
Design Office	404
Departmental Library	1,064
Photographic Services	1,169
Technical Physics	3,080
Glass Laboratory	498
Workshop	38,068
Stores	10,869
Administration	2,803
Total Expenditure	£364,538

Academic Staff Meetings

At the Professors' meeting on 13 January 1970, Prof. Massey recalled the requirements of the Professorial Board that each department should hold not less than two meetings of departmental staff in each session. He felt that such meetings were not adequate for good consultation amongst the staff, and asked what other arrangements could be made that might improve consultation. After extensive discussion it was agreed to make no changes in the existing arrangements for departmental staff or professors' meetings. There followed two Academic Staff Meetings on 22 May and 10 June, the first dealing with matters of general interest and the second with undergraduate syllabuses, teaching and examination methods.

The first meeting considered Communication Problems, Student Complaints, Libraries, Course Content, Lecture Theatres, and Educational Policy. There resulted a Departmental NewsLetter with seven issues from June 1970 to April 1971, and two special departmental lectures - 'A Personal View of High-energy Physics' by Prof. Heymann and 'X-ray Astronomy' by Prof. Boyd; the continuation of Prof. Massey's meetings once a term with representatives of each undergraduate year; a report of the student subscription lending library, controlled by the Library Sub-committee of the Staff-Student Consultative Committee; and the initiation of a central record of topics treated in sequence in courses. Attention was directed to College policy encouraging new members of staff to attend courses such as the 'Introductory Teaching Course for Lecturers 1971' to be given by the University Teaching Methods Unit at the Institute of Education. Prof. Massey expressed his views on possible changes in higher education which would affect the department, mentioning the increasing popular demand for higher education and the 'swing' from science as recorded in the Dainton report; the problem of retaining a good student intake into the department and the policy of concentration on specialised courses might need reconsideration. The meeting closed at 1.05 pm, having started at 10.30 am.

The second meeting considered proposals from the reconstituted Committee for Syllabus Revision (membership Burhop, Bullock, Castillejo (Chairman), B. G. Duff, Fox and Seaton) following its review of the syllabuses of the first-year courses, including a consultation of Duff with other first-year teachers. There followed a revision and a re-scheduling of the B1 and B11 courses, the former consisting of (i) mathematical techniques and (ii) pure mathematics (including 15 problem classes), and the latter consisting of (a) ideas of classical physics and survey of modern physics with (b) mathematical physics. Lectures in the first six weeks of the first term were confined to five per week of (a) and six per week of (i), the mathematical techniques being taught by a physicist. The number of first-year lectures was reduced by about 10% by unification of topics previously scattered throughout the courses, but mainly in the reduction of the lectures in the previous B1.

Two meetings were held in June 1971, the first dealing with general matters, e. g.,SRC Physics Committee proposals for course training for postgraduate students; amendments to University Regulations for Ph.D. permitting award of M.Phil. to Ph. D. candidates; technical staff restructuring; and the departmental situation in College - commencement next session of Executive Committee of the Professorial Board; College resources and their allocation; and Takeover, Letter from SRC chairman. The second considered proposals for changes to second-year courses, based on teachers' suggested revisions and Syllabus Revision Committee amendments designed to reduce content and lectures, to unify content of each unit and relate it clearly to the others, and to integrate theory with applications. Meetings continued to be held during Massey's tenure of the Quain chair and thereafter by his successors.

Staff-Student Consultative Committee

Following the recommendation of the Joint Committee (of the College Committee and Professorial Board) on Student Matters, this committee was formed primarily to improve staff-student relations; provided opportunities for the interchange of ideas or matters affecting students within the department and, when appropriate to make recommendations to the Head of the Department. It held its first meeting on 13 January 1969, the membership, with Prof. Massey's agreement, being 1 Professor (L. Castillejo), 1 Reader (R. E. Jennings), 1 Lecturer (A. J. Metheringham), Tutor to undergraduate Physics Students (J. W. Fox), 2 Postgraduate Students (K. S. Barnes & D. E. Burgess), 1 Third-year Student (Miss J. E. M. Cook), 1 Second-year Student (A. J. Morris) and 1 First-year student (J. C. Palfreman), the student members being elected being by their colleagues. Mr. Metheringham and Miss Cook were elected Chairman and Secretary respectively, although Miss Cook resigned on being elected Administrative Vice-President of the Students' Union in March and was replaced by Mr. Barnes. It held three further meetings during the session, considering three major topics on the basis of submitted reports, namely the structure of the B. Sc. course-unit degree, undergraduate tutorials, and practical work, Drs. G. R. Heyland, F. W. Bullock and G. J. Lush, staff in charge of the third, second, and first-year laboratories respectively being present for the last topic. A number of recommendations were made to Prof. Massey, the most significant being the establishment of a personal tutor system, the provision of model answers to the weekly problems to students and their tutors, and the re-organization of departmental notice boards; all were approved by Prof. Massey and put into effect. Following a discussion of the availability of undergraduate textbooks in the Physical Sciences Library, a Departmental Undergraduate Library was instituted and a Library Sub-Committe formed to be responsible for its operation. The membership of the sub-committee was the three undergraduate representatives of the Staff-Student Consultative Committee, one member of the academic staff appointed by that committee (A. J. Metheringham), the Librarian (Mr. C. A. R. Tayler, the Laboratory Superintendent), appointed by the Department, and three further undergraduates, one elected from each year. Four or five of each of the main textbooks and two or three of the others were housed in a small room attached to the first-year laboratory, one of each text being retained for use in the library, the rest being available for loan for one week, not renewable by the same borrower for the next week. The first meeting of the sub-committee was held on 26 October 1970 under the Chairmanship of Mr. Metheringham, Mr. C. A. R.Tayler, being elected Treasurer, and Miss L. J. Passmore as Secretary. A membership subscription of £6 was agreed with a third depreciation for the session. Mr. Tayler reported a membership of 86 of 143 undergraduates, 80, 58, and 42% of the first, second and third-year undergraduates respectively; the library had 203 books, 107 of which had been issued during its opening eight days. Mr. Metheringham reported that £550 had been spent on buying books, a £50-order being outstanding; including second-hand books costing £72, the average discount was c.11%, the expenditure being necessarily before any receipt of subscriptions.

Students' Societies

The oldest society having a membership involving physics and chemistry staff and students was the Chemical and Physical Society, first founded in 1834, but it did not last long, being absent form the first listing of societies in the 1854 Calendar; refounded on 9 November 1876, Oliver Lodge, then a part-time demonstrator in the department, was elected as President. The other old society embracing members of the mathematics and physics departments was the Mathematical and Physical Society, first listed in the 1903 Calendar. 1950 being the year for a 'Physics President' of the former society, Massey became President on taking up the Quain professorship. A new society, the Carey Foster Society, was formed just after Massey's entry to the department, more emphasis being placed on the social side of the student membership, e. g., welcoming freshers on the night before the commencement of the session, introducing them to the Carey Foster coffee room and showing them some of the department and college. The Astronomical Society, first listed in the 1959 Calendar, continued to thrive after the formation of the joint department. Both societies were mentioned under 'Living in London - Social Activities' in the departmental booklets containing information for prospective undergraduates, namely "these societies promote staff-student contact and enliven the social life of the department, by organising a variety of functions ranging from discos and cheese and wine parties to lectures by distinguished scientists."

Tea parties

Besides the departmental welcome party for freshers, parties were regularly held in the Men's Staff Common (later the Housman) Room each session for first, second, and third-year students. Additionally Massey, a professor and Fox regularly had tea in his room with delegations of students from each year. On one occasion, in 1970 Massey, Seaton and Fox met the whole second-year class at their request in place of the usual tea; among the matters discussed were some criticisms of their teaching and the assessment of course work. On another occasion, the Slade Film Unit shot scenes of the party in Massey's room involving him with Wilson, Fox and a third-year group; some were incorporated in the first College Film, copies of which were loaned to schools, Local Education Authorities, etc. primarily to aid recruitment of students.

Cumberland Lodge Weekend

The King George VI and Queen Elizabeth Foundation of St. Catherine's, established in 1947, is based at Cumberland Lodge in Windsor Great Park, its main concern being with the universities, particularly university students. The departmental week-end started in the 1963-64 session after some visits by a group of members of the Departments of Physiology, Psychology and Physics, organised by Denis Noble of Physiology. The first weekend, from 24-27 April 1964, was entitled 'Attitudes and Methods in Physical Research' and involved an introductory session, 'Why Research?' by E. H. S. Burhop, after dinner on the Friday evening. On Saturday morning there were two sessions; 'Research - Pure or Applied?' by D. W. O. Heddle and M. J. B. Duff, and 'Experimental and Theoretical Approaches' by J. B. Hasted and S. Zienau. After tea Sir Harrie Massey discussed 'The Research Programme of the Department' and after dinner there was 'Laboratories in extensio' by F. F. Heymann and A. P. Willmore. On Sunday there were two sessions, one before and the other after dinner; the former being 'Not only Physicists' by D. G. Davis and F. R. Stannard, and the latter,'Undergraduate Courses - A Preparation for Research' by C. Dodd. There were some 50 participants, half being third-year students. A second weekend took place in 1964, namely from 27-30 November, 'Aspects of University Research in Physics' by R. L. F. Boyd, A. Donnachie and H. B. Gilbody being followed by 'Research in an Industrial Laboratory' by G. A. Gough of Hawker Siddeley Dynamics Ltd. and 'Research in a National Laboratory' by G. H. Stafford of the Rutherford High Energy Laboratory. The November 1965 weekend on 'Experiment and Theory in Modern Physics' included a Saturday evening session on 'St. Catharine's' by Anthony Bland, the Principal of the Foundation. The opening session of the 1966 November weekend, 'Physicists - Supply and Demand', covered a survey of published material on the employment of physicists, and the pre-luncheon session on Saturday, 'Careers for Physicists' was given by R. C. Brown, who had succeeded Orson Wood as the College Careers Adviser in 1961. The Sunday evening sessions were 'The Impact of Computers on Research' by F. F. Heymann and 'Undergraduate Teaching', a discussion started by J. W. Fox.

I succeeded Douglas Davis as organiser of the weekends for the fifth, held from 26-29 January 1968, until my retirement from the department in September 1983. The records show 41 third-year undergraduates, 4 postgraduates, 11 members of staff staying and 5 visiting the Lodge - a full complement! The students were charged £1 each, the department paying a subsidy of £2.5 for each of them. The opening session after dinner was 'How an ethologist might see a physicist' by L. Castillejo. Three of the Saturday sessionswere 'Atomic Physics as a Career', R. F. Stebbings; 'New Forms of Astronomy', A. P. Willmore; 'High Energy Nuclear Physics as a Career', F. F. Heymann, the fourth being the usual pre-prandial one by Sir Harrie Massey. The two Sunday sessions were 'Big Science' by E. H. S. Burhop and 'A Discussionof Undergraduate Problems' under my Chairmanship.

In later years the weekend, starting on the last Friday in October, proved the most convenient; some second-year students were included in the party, some staff continued to stay for the whole week-end, others visiting, and Massey always coming on Saturdays at tea-time for his session between tea and dinner. A 52-seater coach was used to take the students and me to and from the Lodge. The programme of the week-end of 25-28 October 1974 is reproduced below, this being the last one under Massey's headship. The party comprised 53 undergraduates, 5 postgraduates and 19 staff, including Ian McKellar, the College Careers' Adviser.

Friday:25 October
6.45 pm Sherry Party
7.15 pm Dinner
8.45 pm UCL participation in H.E. physics research at C.E.R.N. F. F. Heymann

Saturday: 26 October
8.15 am Breakfast
10.00 am C.U.S.C. - Can computers assist learning? J. McKenzie
11.00 am Tea
11.30 am Observation of compact X-ray sources P. W. Sanford
1.00 pm Lunch
4.30 pm Tea
5.00 pm Sir Harrie Massey
7.15 pm Dinner
8.30 pm Artificial intelligence M. J. B. Duff

Sunday: 27 October
9.00 pm Breakfast
1.00 pm Lunch
4.30 pm Tea
5.00 pm After University I. D. McKellar
7.15 pm Dinner
8.15 pm General discussion Chairman: J. W. Fox

Monday: 28 October
8.00 pm Breakfast

As will be seen, there was plenty of free time for staff and students to take advantage of the recreational facilities at the Lodge; occasionally some of them attended the Sunday morning service in the Royal Lodge Chapel.

Annual Cricket Match

Another feature of departmental life was the annual staff/student cricket match played at Shenley, the staff team being captained by Massey. He was a very good cricketer, having played for the Cavendish Club and being captain in 1933 when the club won the Inter-Laboratory cup. He played club cricket regularly at Belfast and then at Chislehurst, where his prowess gained the Hobbs bat, presented by the great man himself. The Australian test wicket-keeper, B. A. Barnett, is recorded as considering him to be a potential professional player. Massey told Bates that his success as a player was mainly due to his exceptionally fast reaction time; Bates (loc cit) adds that he was exceptionally fast at anything dependent on his mental processes - reading, writing, understanding, mathematical analysis.

Institute of Education Courses

In the late sixties and early seventies the department ran a series of triennial courses on Modern Trends in Physics in relation to the work of the Sixth Form for the Institute. The courses were designed for sixth-form teachers of physics and were held in the lecture theatres and laboratories of the department. As an illustration of the courses, the programme for the course held between 29 June and 4 July 1970 is given below; seventeen members of the department and Prof. P. A. Samet, Director of the Computer Centre, were involved in the course. Residential members of the course stayed in the Institute's John Adams Hall; a special collection of books was displayed at the University Book Shop (later Dillons); and members were allowed to use the College General and Physical Science & Engineering Libraries for reference purposes.

After an early evening reception and sherry party at the Institute, including an introduction of the course, on Monday 29 June, the course started at 9.30 a.m. on Tuesday at UCL, the programme being as follows:

Tuesday,30 June:
9.30 am Prof. Burhop; Physics in the seventies
10.20 Discussion
10.35 Coffee
10.55 Prof. Heymann; Elementary particles
11.45 Discussion
12.00 Lunch
2.00 pm Dr. R. C. Brown; Careers for physics graduates
3.30 Tea
4-5.30 Research laboratories open for inspection

Wednesday,1 July:
9.30 am Prof. Boyd; X-ray astronomy
10.20 Discussion
10.35 Coffee
10.55 Dr. Jennings; Infra-red astronomy
11.45 Discussion
12.00 Lunch
2.00 pm Mr. Metheringham; Projects and special courses in undergraduate practical work
3.30 Tea
4-5.30 Undergraduate laboratories open for inspection

Thursday, 2 July:
9.30 am Prof. Seaton; The origin of the chemical elements
10.20 Discussion
10.35 Coffee
10.55 Dr. Griffith; Collisions of positrons with molecules
11.45 Discussion
12.00 Lunch
2.00 pm Dr. Fox; Assessing performance in sixth-form practical physics
3.30 Tea
4-5.30 Research and undergraduate laboratories open for inspection

Friday, 3 July:
9.30 am Dr. Samet; Computer science as an academic discipline
10.30 Discussion
10.35 Coffee
10.55 Scientific films
12.00 Lunch
2-5.30 All laboratories and Computer Centre open for inspection

Saturday, 4 July:
10.00am General discussion, chaired by Mr. Underwood of the Institute
11.00 End of course

It is interesting to note that the course was numbered 930 by the Institute; successive courses were run in 1973 and 1976, but those arranged for 1979 and 1982 were cancelled owing to lack of applicants.

Student Numbers

In 1965, on the advice of Massey, the Provost (Sir Ivor Evans) appointed Dr. A. W. Barton on a part-time basis to help with the recruitment of students into the science departments of the college. Incidentally Barton, the son of E. H. Barton, F.R.S. (one-time Professor of Physics at Nottingham) read physics at Cambridge, being Senior Scholar of Trinity College. After his Ph. D. degree for research in the Cavendish Laboratory, he took up schoolmastering on Rutherford's advice, becoming Chief Physics Master at Repton and successively Headmaster of King Edward VII School, Sheffield and the City of London School. He was a commanding figure in the Headmasters' Conference, and being a first-class soccer referee, was active in the Football Association. He became Advisor for Recruitment of Science Students in 1966 and the first Schools Liaison Officer of the College in 1966. In 1971 Barton was succeeded by Mr. M. W. Brown, a Cambridge mathematician, who had taught at the Bec School, Wilson's Grammar School and Wandsworth Training College before becoming Deputy Head of Peckham Boys' School and then Head of Charlton and Holloway School - the latter being one of the earliest London schools to be re-organised on a comprehensive basis. He joined the I.L.E.A. in 1960 as a District Inspector (Mathematics), becoming a Staff Inspector (General) in 1963. Whereas Barton made his biggest impact in the independent sector, Brown made a complementary contribution mainly in the maintained sector, including the L.E.A. Careers Advisory Service. When the time came to review Brown's appointment, it had become evident that his successor should be chosen from someone with an intimate knowledge of the College, some involvement with the schools, and some experience of the problems faced by admission tutors. Hence my appointment to succeed Brown in 1974 on the recommendation of the Faculty Tutors. With the approval of Massey and his successor, Heymann, I was able to develop the job, devoting as much time to it as seemed in the best interests of the College within the framework of my departmental duties of Head Tutor and Head of the Undergraduate Teaching Group.

Undergraduate admissions during the last ten-year Massey period are tabulated below, the second column recording the total number of candidates applying for physics and the other columns recording the number applying for the relevant UCL courses, the numbers in parenthesis being those admitted.

	National	UCL
Year	Physics	Physics	App/Phys	Chem/Phys	Astron	Astron/Phys
1965	2749	641(42)			58(8)
1966	2367	467(43)			77(10)
1967	2436	358(52)			76(8)
1968	2578	375(54)		22(0)	84(6)
1969	2738	323(47)		49(8)	99(9)
1970	2795	280(35)	42(7)	34(4)	137(23)
1971	3017	268(37)	67(19)	41(9)	132(20)
1972	2807	216(31)	43(9)	46(6)	135(18)
1973	2579	194(24)	46(4)	40(6)	149(22)
1974	2471	158(24)	34(7)	17(2)	113(21)	111(16)
1975	2295	181(30)	22(3)	32(6)	98(30)	110(13)

Drop-out Statistics

For each session from 1968 to 1974, the number of students (percentages in brackets) not proceeding to the second and third year of each course are given in the first and second rows respectively, the analysis in the columns - A(academic failure); B(transfers to other colleges and within UCL); C(left for medical reasons); D(left at own request); E(total) - being normal Faculty of Science procedure.

	Session	Course	A	B	C	D	E
	1968	Phys	4 (7.7)	3 (5.8)	0	1 (1.9)	8 (15.4)
			0	0	1 (2.8)	2 (5.6)	3 (9.4)
		Ast	1 (12.5)	0	0	0	1 (12.5)
			0	0	1 (14.3)	0	1 (14.3)
	1969	Phys	1 (2.0)	2 (4.0)	0	1 (2.0)	4 (8.0)
			4 (9.3)	0	1 (2.3)	0	5 (11.8)
		Ast	0	0	0	0	0
			0	0	0	0	0
	1970	Phys	2 (4.3)	2 (4.3)	0	2 (4.3)	6 (13.0)
			2 (4.3)	0	0	0	2 (4.3)
		Chem/Phys	1 (12.5)	1 (12.5)*	0	0	2 (25.0)
		Ast	1 (11.1)	1 (11.1)	0	0	2 (22.2)
			0	0	0	0	0
				*Chem/Phys: transfer to Phys
	1971	Phys	1 (2.9)	1 (2.9)	0	3 (8.6)	5 (143.4)
		4	(9.8)	0	1 (2.4)	0	5 (12.2)
		App Phys	2 (28.6)	0	0	1 (14.3)	3 (42.9)
		Chem/Phys	0	1 (25.0)*	0	0	1 (25.0)
			0	0	0	0	0
		Ast	1 (4.3)	0	0	1 (4.3)	2 (8.6)
			0	0	0	0	0
				*Chem/Phys: transfer to Phys
	1972	Phys	5 (13.9)	4 (11.1)	0	0	9 (25.0)
			8 (25.0)	0	0	0	8 (25.0)
		App Phys	1 (5.3)	5 (26.3)	0	0	6 (31.6)
			0	0	0	0	0
		Chem/Phys	1 (11.1)	0	0	0	1 (11.1)
			0	0	0	0	0
		Ast	0	0	0	1 (5.0)	1 (5.0)
			5 (23.8)	0	0	0	5 (23.8)
	1973	Phys	4 (12.9)	0	0	0	4 (12.9)
			2 (7.1)	0	0	0	2 (7.1)
		App Phys	1 (11.1)	0	0	0	1 (11.1)
			0	0	0	0	0
		Chem/Phys	0	0	0	0	0
			1 (14.3)	0	0	0	1 (14.3)
		Ast	0	0	0	1 (5.5)	1 (5.5)
			1 (5.3)	1 (5.3)	0	0	2 (10.6)
	1974	Phys	2 (8.3)	0	0	2 (8.3)	4 (16.6)
			0	0	0	0	0
		App Phys	0	0	0	0	0
			0	0	0	0	0
		Chem/Phys	0	1 (50.0)*	0	0	1 (50.0)
			0	0	0	0	0
		Ast	1 (5.9)	0	0	3 (17.6)	4 (23.5)
			2 (11.1)	0	0	1 (5.5)	3 (16.6)
		Ast/Phys	2 (11.8)	5 (29.4)*	0	0	7 (41.2)
				*Chem/Phys: transfer to Chem Eng;  Ast/Phys:3 transfers to Ast, 2 to Phys

Postgraduate Students

The number of postgraduate students in the department increased to 29 in Massey's first session, special lecture courses for them being given in radiation theory, theory of spectra, nuclear physics, and atomic collision phenomena; in addition seminars in nuclear physics, and electronic and ionic physics were regularly held. Throughout substantial coherent courses of lectures and seminars were provided, and all students were required to attend some courses during their first year. Lectures in high energy physics were arranged on a collaborative basis with Queen Mary and Westfield Colleges; those in astronomy and space research, and in atomic and molecular physics were mainly given by departmental staff, with collaboration from some honorary staff in SRC laboratories. A small number of students took courses at other schools of the University, particularly Imperial College.

An M.Sc. course in theoretical physics was given at times during the mid-fifties to the mid-sixties; from 1962 to 1965 it was designated 'M.Sc. course on Theoretical Atomic and High Energy Physics'. The College Diploma in Space Science (one year full-time, two years part-time) was instituted in the 1962-63 session; this course was directed by G. V. Groves, who gave almost all the lectures required (see p. 101).

Dr. M. J. B. Duff was Tutor for Admission of postgraduate students; before the introduction of new M.Phil. research degree (one of the results from the 1965-66 Saunders's Committee on Academic Organization) all research students registered for the Ph. D. degree; afterwards they registered for the M.Phil. for the first year, normally transferring to the Ph.D. in their second year. Massey was keen to recruit his own students, the procedure after the introduction of the course-unit degrees being as follows: after the lunch for the external examiners in the Whistler Room, I announced the degree classifications to the assembled finalists in the small theatre on the fourth floor, finishing by "Professor Massey wishes to see all those having gained first-class honours, and any others who would like to see him". Interviews followed in his room, Messrs. Duff, Fox, D. G. Davis and sometimes Burhop also being present, and SRC studentships were allocated to students, some of whom having previously expressed their preferences for particular research groups.

In 1973 the department received a quota of 11 SRC studentships, namely 3, Nuclear Physics; 3, Space Research; 3, Astronomy; and 2, Physics. 4 studentships were awarded 'on appeal' and 1 as an 'instant', making a total of 16. It was understood that Professor A. H. Cook's panel advising the SRC on the research programme of the Mullard Space Science Laboratory had recommended an increase of 2 in the number of space research studentships. As recorded on p. 70 the Committee reviewing the resources of the department noted that there was an increase of postgraduate students from 65 in 1973 to 70 in 1976, but there was little chance of realising the capacity of 100 owing to the numbers of studentships and suitably qualified candidates then available.

In conclusion further reference is made to Massey's Royal Society Biographical Memoir (B.B.D), following closely Boyd on Space Research, Davis on Scientific Policy, and Bates on the Royal Society etc.

Space Research (1953-78)

M. O. Robins in the preface to the History of British Space Science, written by Massey and Robins, writes "Space Science in Britain was initiated, and the foundations for its development were laid, very largely by one man, the late Sir Harrie Massey". Massey's involvement at the outset has been sketched on p. 87, following his Chairmanships of the Royal Society's Gassiot Committee in 1951, its Rocket Sub-Committee in 1955, and Artificial Satellite Sub-Committee of the National I.G.Y. Committee in 1956. Ten days after the launch of 'Sputnik 1', the Artificial Satellite Sub-Committee met and decided to set up two working parties, one on the scientific value of satellites, the other on radio, optical, and computing methods of study. After the first successful Skylark experiments at Woomera in 1957, the requirements of the national rocket programme and the scientific and policy matters relating to satellites led Massey to set up in the department a Space Management Unit headed by Robins, who was seconded from the Ministry of Supply. The decision of the Bureau of the International Committee of Scientific Unions to establish a special Committee on Space Research (COSPAR) led to Massey's attendance at the preparatory meeting at the Royal Society in November 1959 as the nominee of the British I. G. Y. Committee; the meeting set up a five-man Executive Council, including Massey; and in December the Royal Society decided to appoint a British National Committee on Space Research with Massey as chairman, an office he discharged energetically for a quarter of a century. Massey served as a Bureau member of COSPAR until 1978 and the importance of his role in the National and International Space scene at this seminal time cannot be overestimated.

As soon as it existed, Massey led the National Committee into a study of the U. K. way ahead by setting up two sub-committees, one for Tracking and Data Recovery, the other for Design of Experiments. The latter, under his chairmanship, immediately considered the provision of satellite flight opportunities for British scientists. There resulted the development of the U. K. launching system at Woomera, with Commonwealth cooperation, opportunities on American rockets, and European cooperation. A launcher development based on the Blue Streak intermediate range ballistic missile project, possibly using a development of Black Knight as the second stage was considered with the view of orbiting a stabilized ultra-violet telescope. In the event the Prospero satellite launched into orbit by a Black Arrow vehicle on 28 October 1971 was the only all-British launching system. However Massey's big-thinking approach led to the successful IUE collaboration of the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) of the USA.

As recorded on p. 88, NASA'S offer to launch suitable space experiments without charge for other countries led to the launching of Ariel 1 on 26 April 1962. Within six weeks of the offer, Massey had set up working groups of his Design of Experiments Sub-committee in seven different disciplines to make proposals for suitable experiments. The unusual method of financing the NASA-UK cooperative space programme owed much to Massey's personality and his dedication to university science: namely, a Steering Group, including Massey, set up within the office of the Lord President of the Council, who was also Minister for Science, had responsibility within the Government for space policy and finance, but the scientific programme rested with the British National Committe for Space Research, that was Massey and the Royal Society, financial caring being carried out by the Department of Scientific and Industrial Research (DSIR).

During the late fifties and early sixties Massey sought to share his vision and enthusiasm with scientists and statesmen in Australia, Canada, India, New Zealand and Pakistan. He became Chairman of an informal Consultative Space Research Committee, which met in Colombo, Ceylon in 1968 and planned a useful programme of mesospheric and lower ionospheric research.

Massey played a key role in bringing about the European Space Research Organization (ESRO), which arose following the success of CERN at Geneva. It was discussed with Massey at the COSPAR meeting in January 1960, and after a small meeting with senior European scientists in February, he arranged a more formal meeting in April at the Royal Society by invitation of the British National Committee on Space Research. Although absent in Australia, the studies of working groups he had set up earlier, together with the Skylark experience and the start on UK-1 (Ariel 1), enabled the UK to play a leading part at the meeting. There followed the formal establishment of a Preparatory Commission for European Space Research, which held its first meeting in Paris on 13-14 March. Massey was elected chairman of a small bureau to make arrangements for an intercontinental meeting to set up the Commission; consequently he chaired a meeting for technical discussion at the Royal Society. The intergovernmental meeting was held in Geneva on 28 November, Massey being elected chairman and presiding as he called the head of each government's delegation to sign the protocol. When the Commission convened in Paris in the early Spring, he was elected President, both of the Commission and its inner bureau. More than three years elapsed before the first meeting of the ESRO Council, during which Massey's energy at home and diplomacy abroad not only set the mould of ESRO for years ahead, but also got a research programme agreed and started before the organization had been ratified.

Massey relinquished his Chairmanship of the ESRO Council towards the end of 1964. His appointment as Chairman of the Council of Scientific Policy (CSP) in January 1965 restricted his activities on space research affairs, although he was frequently consulted by ESRO and its successor, the European Space Agency (ESA). The establishment of the Research Councils resulted in the removal of the executive control of UK space research policy from the Royal Society's National Committee to the Science Research Council (SRC). However Massey continued to attend meetings of the Astronomy Space and Radio Board and of the SRC influencing policy. His frustration at not getting any of the ESRO institutes in the UK probably led to the acquisition of the Mullard Space Science Laboratory at Holmbury House in 1965, recorded on p. 61.

ESA had a wider remit than ESRO and in 1972 its scientific programme was giving grounds for concern. Massey saw that NASA had managed to maintain a prime role for space science benefiting from its close consultations with the Space Board of the National Academy of Sciences. He called together senior European space scientists and became Chairman of a Provisional Space Science Board for Europe, having representative exchange with the corresponding USA Board. In 1974 the European Board became the Standing Committee on Space Research of the European Science Foundation, Massey being Chairman until 1978.

Science Policy (1953-83)

Massey's early involvement in science policy was in areas of physics in which he was particularly interested, namely space and nuclear physics research. He was a member of the Department of Scientific and Industrial Research (DSIR) Nuclear Physics Sub-Committee from 1956; the Research Grants Committee from 1959; and the Governing body of the National Institute for Research in Nuclear Science from its foundation in 1957. In January 1965 the Secretary of State for Education and Science appointed the Council for Scientific Policy to advise him on civil science policy, Massey being Chairman. At the same time a Bill was going through Parliament, which became the Science and Technology Act 1965, providing for the establishment by Royal Charter of the Science and Natural Environmental Research Councils, and for the transfer to them of many of the former functions of the DSIR, which was then dissolved. The Research Councils were financed directly by the Department of Education and Science and the industrial research responsibilities of the DSIR were transferred to the Ministry of Technology. The full members of the CSP were all distinguished scientists and the heads of the four Research councils and the Chairman of the UGC were assessors. The CSP was required to provide both general advice on civil science policy and also specific advice on the programmes and financial needs of the Research Councils. During the previous decade Research Council expenditure had grown at an annual rate of around 13% in real terms and it was necessary to find a way towards a rate much closer to the GNP rate without serious damage to science. Massey set up working parties to study the problem; the Research Councils were invited to consider their long-term programmes and to develop the justification for their policies, 'both in terms of intrinsic scientific criteria and in relation to their educational, social and economic benefits'.

Some of the studies were toward specific measures to improve the 'scientific environment'. The first group to report was that chaired by Prof. B. H. Flowers on computers for research; it recommended a major programme of computer installation in the universities and research councils over a five-year period and the establishment of a Computer Board to coordinate the assessment of computing needs and provision. The proposals were strongly endorsed by the CSP and they were accepted by the Government at the end of 1965, with implementation over six rather than five years. Another group, chaired by Sir Gordon Sutherland, studied liaison between universities and Governmental research establishments. Its report in March 1967 dealing with the outstanding success of the Medical Research Council Unit in Molecular Biology not being balanced by a comparable development in teaching the subject led to the Group on Molecular Biology, chaired by Dr. J. C. Kendrew, examining the field and reporting back in July 1968.

Some evidence of a trend away from science in school sixth forms led to a working party, chaired by Prof. F. S. Dainton, set up to enquire into the flow of candidates in science and technology into higher education; it included members of the Committee on Manpower Resources for Science and Technology and produced an interim report in February 1966.

Massey always considered the universities to be the main centre of scientific activity, and the CSP appointed a group under his chairmanship 'to consider, with representatives of the University Grants Committee, how best to examine fully the policy and machinery for the support of research in the universities'. This led in April 1967 to a joint working group of the CSP and UGC 'to study criteria for the development of the system of support for scientific research in the universities giving particular attention to the implications of retaining initiative and freedom of manoeuvre for the individual researcher'. Again Massey led this group, which reported in October 1971, after the end of his chairmanship of the CSP. The report constitutes one of the most cogent statements for the continuation of the 'dual support system' of the UGC and the Research Councils

The CSP regarded international scientific relations as of the utmost importance and established a standing committee, with Massey as chairman, on the subject, the membership including representatives of the Royal Society and appropriate Governmental departments. A wide range of topics were considered, including measures to promote mobility of European scientists, and the possibility of European cooperation in molecular biology. The first led to a European fellowship scheme, administered by the Royal Society, and the second contributed to the establishment of the European Molecular Biology Organization some years later.

As recorded on p. 61, Burhop spent the 1962-63 session at CERN serving as secretary of the Amaldi Committee considering the future policy for accelerators in Europe. Its first proposal was accepted, the Intersecting Storage Rings being built. The second proposal resulted in further studies, culminating in detailed proposals to the CERN Council for a 300 GeV machine. Nine possible sites for the machine, including one at Mundford in Norfolk, were considered. In March 1967 the CSP set up a working group, chaired by Prof. M. M. Swann, to examine the implications of the proposed accelerator for the balance of the UK scientific effort, both national and international; and to assess the wider effects of implementing the proposal. The Nuclear Physics Board of the SRC strongly backed the proposal, but the SRC was naturally more divided. The SRC included provision for UK participation in the proposed accelerator in the Five-Year Forward Look submitted to the Department of Education and Science in May 1967, and advised the Secretary of State that the UK participation should be subject to various safeguards, the most important being the protection of the proper development of other disciplines; Massey and Nyholm formally dissented. The proposal presented the CSP with the 'big science versus little science' dilemma in stark form. The CSP endorsed the SRC recommendation, noting that the cost could be accommodated in a nuclear physics budget rising at an average annual rate of 7%, and recommending that the balance in favour of other fields of science should be redressed by an annual growth over the next decade of 9%. The various reports, including an economic assessment of the siting a 300 GeV laboratory in the UK instead of in another CERN member state, were published in January 1968. Although the SRC was prepared to accept lower growth rates and reduce the national programme of nuclear physics, the government in June 1968 decided on financial grounds against the participation of the UK in the 300 GeV project. The eventual outcome turned to be a happy one; after some protracted international discussions over costs and sites and further design studies, led by Dr. J. B. Adams, who had been a member of the CSP, revised cheaper proposals were accepted by the CERN Council in February 1971, with the support of the UK delegate, for a Super Proton Synchrotron at CERN using the existing Proton Synchrotron as an injector. This machine was built under Adams's direction, and members of the department, e.g., the Emulsion Group (see p. 80), were prominent among its users.

During Massey's chairmanship of the CSP a series of Science Policy Studies were published, mostly by members of the Secretariat, covering issues such as 'The sophistication factor in science expenditure' and 'An attempt to quantify the economic benefits of scientific research' on topics of interest to the CSP. Massey's term of office as chairman of the CSP finished at the end of 1969.

One important field of science policy in which Massey played a unique role was in UK-Australian collaboration. In the mid-sixties proposals for a major optical telescope in Australia were under discussion and in 1966 the SRC decided to give high priority for a joint UK-Australian 150 inch optical telescope. Massey supported the project on the grounds of being the most practicable way of providing good observing facilities in the Southern Hemisphere for British and Australian astronomers, and he helped the project along during its formative period. The construction of the telescope started in 1967, but the replacement of a Joint Policy Committee of the Australian Department of Education and Science and the SRC by the Anglo-Australian Telescope Board had to await the passing of the Anglo-Australian Telescope Agreement Act by the Australian Parliament in 1970. Massey was appointed a UK member of the Board, as Deputy Chairman in 1975 when the telescope was passing from the commissioning to the operational stage, and in 1980 he became Chairman, holding the office until 1983. At a Board meeting, which he was too ill to attend, it was decided to name the base laboratory in Epping after him.

After being Chairman of the CSP, Massey undertook fresh responsibilities: Physical Secretary of the Royal Society, 1969; Vice-Provost of UCL, 1969; Royal Society assessor on both the Astronomy and the Space Policy and Grants Committees of the SRC's Astronomy, Space and Radio Board, continuing in the latter role through various changes in the organization of the SRC, including the change of name to Science and Engineering Council.

Royal Society: Council Service (1949-51), (1959-60); Physical Secretary and Vice-President (1969-78).

An officer who served on the Council with Massey, The Treasurer, Sir John Mason, wrote "One of Massey's greatest contributions to the promotion and support of science in his later years was his outstanding service as Physical Secretary of the Royal Society. He held this onerous position for an unusually long period of nine years, from 1969-1978, serving under three presidents, Blackett, Hodgkin and Todd. In this office, which gave him much pleasure and satisfaction, Harrie Massey brought all his great gifts of creativity, wisdom, foresight and energy to bear on a whole range of issues under consideration by the Society as it was extending the scale and scope of its national and international activities and taking a much more active and positive role in science policy and public affairs."

He goes on to recall Massey's involvement in the controversial discussions on the organization and management of governmental research and development, culminating in the Rothschild proposals on which he had strong reservations; his even more decisive role after the Executive Secretary, Sir David Martin, died suddenly in December 1976 when the Treasurer, Biological Secretary and Foreign Secretary had been in office for only two weeks and the President for only a year. Harrie Massey kept "the ship on an even keel while the new crew was learning the ropes and it was largely due to his excellent judgement and calm authority, derived from a vast experience of people and situations, that the Society was able to undertake many new initiatives and changes with little disruption or dissension".

He refers to one of Massey's major tasks, namely, to chair a committee set up by the Society to review the functions and operations of the Ordnance Survey; this complex study starting in 1973, led to major representations to the Serpell Committee in 1979, and to further representations to the Secretary of State for the Environment in 1981.

Mason recalls Massey organizing, with others, a scientific discussion meeting almost every year from 1973 to 1980 with three separate discussions in both 1974/5 and 1977/8. He concludes with a supplement of undertakings additional to what might be thought of as the normal duties as Physical Secretary; some 30 items are listed, starting with 1970 March, R.S. delegation to Japan and ending with 1980 December, further submissions on Ordnance Survey.

Honours and Distinctions

The Sovereign: Knight Bachelor 1960.
Royal Society: Fellow 1940; Hughes Medal 1955; Royal Medal 1958; Rutherford Memorial Lecture 1967;
Council Service 1949-51, 1959-60; Physical Secretary and Vice-President, 1969-78.
Other learned societies: Royal Astronomical Society: Vice-President 1950-53, Gold Medal 1982. Honorary
Member, Royal Meteorological Society 1967. Physical Society: President 1954-56, Honorary Fellow 1976. Corresponding Member of Australian Academy of Science 1976, of Academy of Science, Liege 1967. Member, American Philosophical Society 1975.
Universities: Honorary Doctorates: Melbourne 1955, Belfast 1960, Glasgow 1962, Leicester 1964, Hull 1968,
Western Ontario 1970, Melbourne (again) 1974, Adelaide 1974, Heriot-Watt 1975, Liverpool 1975, York 1981, Ontario 1981. Honorary Fellow, University College London 1976.
Miscellaneous: Founder Member, Atomic Scientists Association, Vice-President 1949-53, President 1953-57. Anglo-Australian base laboratory building, named Massey Building 1984. Member, Middlesex County cricket Club and Melbourne Cricket Club; Awarded Hobbs cricket bat 1939.

Publications

Books (and lectures, separately published) The theory of atomic collisions (with N.F.Mott) 1933; Oxford, Clarendon Press, (2nd & 3rd edn, 1949 & 1965).
Negative Ions 1938; Cambridge Univ Press, (2nd & 3rd edn, 1950 & 1976).
The atom and its nucleus 1950; Univ of Queensland, Brisbane.
Electronic and ionic impact phenomena (with E.H.S.Burhop) 1952; Oxford, Clarendon Press, (2nd edn with H.B.Gilbody, also 5 vols., 1969-1974).
Atoms and Energy 1953; London, Elek Books, (2nd edn, 1956).
The upper atmosphere (with R.L.F.Boyd) 1958; London, Hutchinson, (2nd edn, 1960).
Ancillary Mathematics (with H. Kestelman) 1959; London, Pitman, (2nd edn, 1964).
The new age in physics 1960; London, Elek Books, (2nd edn, 1967).
Basic laws of matter (with A.R.Quinton) 1961; Bronxville, N.Y., Herald Books.
Scientific research in space (with M.O.Robins, R.L.F.Boyd, G.V.Groves & D.W.O.Heddle) 1964; London, Elek Books.
Space Physics 1964; Cambridge Univ Press.
Space travel and exploration 1966; London, Taylor & Francis.
Atomic and molecular collisions 1979; London, Taylor & Francis.
History of British space research (with M.O.Robins); 1984; Cambridge Univ Press.
Applied atomic collision physics 1982 (Editor with E.W.McDaniel & B.Bedserson, 5 vol); N.Y. Academic Press.
Negative ions by B.M.Smirov, translated by S. Chomet (Editor) 1982; London, McGraw-Hill.
Report of a study on the support of scientific research in the universities (commissioned by the Council for Science Policy) 1971; London, H.M.S.O. (Cmnd 4798).

Scientific papers

221 are listed in B.B.D., starting with 'The theory of the extraction of electrons from metals by positive ions and metastable atoms' (Proc Camb Phil Soc 26,386-401 and ending with 'Summary lecture in Fundamental processes in energetic atomic collisions' (ed H.O.Lutz, J.S.Briggs & H. Kleinpoppen), pp. 659-668; N.Y. Plenum Press. After his retirement in 1975, Massey regularly came into the department, Margaret Harding, the departmental secretary, continuing to do some of his work; despite his long painful illness, he soldiered on, towards the end, coming in with an arm in a sling. Massey died from bone cancer on 27 November 1983; Sir David Bates gave the address at his funeral service on 2 December in Christ Church, Esher, the coffin being draped with the Australian flag. Some members of the department attending the service accompanied the family to the interment in Long Ditton cemetery

A Memorial Service was held for Sir Harrie at noon on Thursday 8 March 1984 in The University Church of Christ the King in Gordon Square, WC1. Sir David Bates delivered the address, the Provost, Sir James Lighthill, and the President of the Royal Society, Lord Todd, read.

The College established an Appeal Fund to honour Massey's memory, income from the fund supporting the Massey Medal, awarded biennially to an individual making an outstanding contribution to space research, the recipient being selected by the Royal Society on the basis of nominations by COSPAR and presented at the Plenary Sessions of COSPAR; and an annual Massey Memorial Lecture commemorating his outstanding service to science and to the College.

REFERENCES

B	Bellot, H. Hale: University College London, 1826-1926; Univ. of London Press Ltd., 1929.
D.N.B.	Dictionary of National Biography.
D.L.U.	Description of the London University, 1828; (College Archives).
W	Wood, D.O.: About the Physics Department, University College London  and those who worked therein, 1826-1950 (Typescript, College Archives).
K	Ker, W.P.: Editor, Notes and Materials for the History of U. C. L. (College Archives).
P	Porter, A.W.: Department of Physics (Typescript, College Archives).
G	Grant, W.: Manuscript dealing with the history of the College in general  and of the Physical Department in particular (College Archives).
H & N	Harte, N. & North, J.: The World of University College London 1828-1978; Published by U.C.L.
M & R	Massey, Sir Harrie & Robins, M.O.: History of British Space Research; Cambridge Univ. Press 1986.
B.B.D.	Bates, Sir David; Boyd, Sir Robert & Davis, D.G.: Harrie Stewart Wilson Massey, 1908-1983;  Royal Society Biographical Memoir, Volume 30, November 1984.

Other:
College Archives consulted were Annual Reports from 1827 onwards; Calendars - London University, 1831, UCL 1853/4 onwards; Distribution of Prizes and Certificates of Honour, 1828/9-1851/2.
Manuscripts were Minutes, Council 1825-1907, then Committee 1908 onwards.
Apparatus Book, Natural Philosophy, 1827-30; Apparatus Book, 1862 and a somewhat earlier version thereof; List of Physical Apparatus, 1866-73.
Attendance Register, 1881-92.
The Admission of Women to University College London; A Centenary Lecture; N.B.Harte, UCL 1979.
Department of Physics Research Reports (ed. M.J.B.Duff) 1964/5, 1965/6, 1966/7, 1967/8, 1968/9.
Numerous papers in Scientific Journals, some specified in the text, most not.
Department of Physics Newsletters (ed. D.G.Davis) No. 1-7, June 1970-April 1971.
Report of the ad hoc Committee on the Resources Survey and Headship of the Dept of Physics & Astronomy; App. Executive Committee (D) 76/1/2.
Royal Society Obituary Notices:-
  George Carey Foster 1835-1919, A.H.Fison.
  Hugh Longbourne Callendar 1863-1930, S.W.J.S.
  Frederick Thomas Trouton 1863-1922, A.W.Porter.
  William Henry Bragg 1862-1942, E.N. da C. Andrade.
  Alfred William Porter 1863-1939, A.O.Rankine.
Royal Society Biographical Memoirs:-
  Edward Neville da Costa Andrade 1887-1971, A. Cottrell.
  Eric Henry Stoneley Burhop 1911-1980, Sir Harrie Massey & D.H.Davis.
  Harrie Stewart Wilson Massey 1908-1983, Sir David Bates, Sir Robert Boyd & D.G.Davis.

Other papers:-
Callendar, L.H. 1967: Professor H. L. Callendar, C.B.E., M.A., LL.D., F.R.S. (Life of father).
  Phys. Bull., April, 1961, 87-90.
Andrade, E.N. da C. 1966: A physics research student at Heidelberg in the old days.
  Physics Education, Vol.1, No.2, 69-78, July 1966.
Burhop, E.H.S. 1968: H.S.W.Massey - a sixtieth birthday tribute.
  Adv. Atomic Molec. Phys. 4, 1-11.
Bates, D.R. 1985: H.W.S.Massey, life, work, personality and characteristics.
  In 'Fundamental processes in atomic collision physics' (ed. H. Kleinpoppen)
  (Proc. NATO Summer School 1984) N.Y. Plenum Press.

References

B	Bellot, H. Hale: University College London, 1826-1926; Univ. of London Press Ltd., 1929.
D.N.B.	Dictionary of National Biography.
D.L.U.	Description of the London University, 1828; (College Archives).
W	Wood, D.O.: About the Physics Department, University College London  and those who worked therein, 1826-1950 (Typescript, College Archives).
K	Ker, W.P.: Editor, Notes and Materials for the History of U. C. L. (College Archives).
P	Porter, A.W.: Department of Physics (Typescript, College Archives).
G	Grant, W.: Manuscript dealing with the history of the College in general and of the Physical Department in particular (College Archives).
H & N	Harte, N. & North, J.: The World of University College London 1828-1978; Published by U.C.L.
M & R	Massey, Sir Harrie & Robins, M.O.: History of British Space Research; Cambridge Univ. Press 1986.
B.B.D.	Bates, Sir David; Boyd, Sir Robert & Davis, D.G.: Harrie Stewart Wilson Massey, 1908-1983; Royal Society Biographical Memoir, Volume 30, November 1984.

Other:
College Archives consulted were Annual Reports from 1827 onwards; Calendars - London University, 1831, UCL 1853/4 onwards; Distribution of Prizes and Certificates of Honour, 1828/9-1851/2.
Manuscripts were Minutes, Council 1825-1907, then Committee 1908 onwards.
Apparatus Book, Natural Philosophy, 1827-30; Apparatus Book, 1862 and a somewhat earlier version thereof; List of Physical Apparatus, 1866-73.
Attendance Register, 1881-92.
The Admission of Women to University College London; A Centenary Lecture; N.B.Harte, UCL 1979.
Department of Physics Research Reports (ed. M.J.B.Duff) 1964/5, 1965/6, 1966/7, 1967/8, 1968/9.
Numerous papers in Scientific Journals, some specified in the text, most not.
Department of Physics Newsletters (ed. D.G.Davis) No. 1-7, June 1970-April 1971.
Report of the ad hoc Committee on the Resources Survey and Headship of the Dept of Physics & Astronomy; App. Executive Committee (D) 76/1/2.
Royal Society Obituary Notices:-
  George Carey Foster 1835-1919, A.H.Fison.
  Hugh Longbourne Callendar 1863-1930, S.W.J.S.
  Frederick Thomas Trouton 1863-1922, A.W.Porter.
  William Henry Bragg 1862-1942, E.N. da C. Andrade.
  Alfred William Porter 1863-1939, A.O.Rankine.
Royal Society Biographical Memoirs:-
  Edward Neville da Costa Andrade 1887-1971, A. Cottrell.
  Eric Henry Stoneley Burhop 1911-1980, Sir Harrie Massey & D.H.Davis.
  Harrie Stewart Wilson Massey 1908-1983, Sir David Bates, Sir Robert Boyd & D.G.Davis.

Other papers:-
Callendar, L.H. 1967: Professor H. L. Callendar, C.B.E., M.A., LL.D., F.R.S. (Life of father).
Phys. Bull., April, 1961, 87-90.
Andrade, E.N. da C. 1966: A physics research student at Heidelberg in the old days.
Physics Education, Vol.1, No.2, 69-78, July 1966.
Burhop, E.H.S. 1968: H.S.W.Massey - a sixtieth birthday tribute. Adv. Atomic Molec. Phys. 4, 1-11.
Bates, D.R. 1985: H.W.S.Massey, life, work, personality and characteristics. In 'Fundamental processes in atomic collision physics' (ed. H. Kleinpoppen) (Proc. NATO Summer School 1984) N.Y. Plenum Press.

Acknowledgements

Finally, I must record my thanks to Michael Duff, who translated my manuscript into Word, and to John McKenzie, who has done all the work, including the insertion of the photographs, on including the document in the Departmental web site.