UCL Centre for Digital Humanities


Book that opens to show an abacus

Special Collections has a curious leather-bound book (GRAVES 121.k.4) that opens to reveal an abacus. The inscriptions suggest it is French and from the 18th Century (Figure 1).

Abacus Book

The abacus consists of moveable beads held on rigid metal wires and we were asked if we could find out what the beads were made of. They were either ivory or bone, but the conservation process is different for each.

The chemical composition of ivory and bone are very similar, both being a mixture of collagen and minerals. However, because they grow differently, the structure of the two differs. CITES, the Convention on International Trade in Endangered Species, provides a useful guide for identifying ivory that explains that ivory is tooth-like with cross-hatchings, whereas bone contains tubes and pits through which fluid flows.

Using a microscope, we acquired close-up images of some of the beads (Figure 2). These show the pits and tubes (called a Haversian System) that are characteristic of bone.


We then took the opportunity to test out photogrammetry on this book. We took 44 photographs (Figure 3).

Abacus Book animation

Using software called Agisoft Photoscan, we were able to render these photographs into an interactive 3D model

The model is clearly not perfect. The wires holding the beads have not rendered well. However, we hope that with improved lighting, we can reacquire new photographs and create an improved interactive model.