The anonymous author was in fact Francis Green (1742-1809) whose son attended Thomas Braidwood's Edinburgh school.
Green, who was born in Boston, served in the British army as an officer for nine years. Remaining a loyalist in the War of Independence, he left for Britain in 1780, where his eight year old son was educated in Braidwood's Academy for the next six years. He returned to Halifax, Nova Scotia & later Medford, Massachusetts where he continued his interest in deaf education, translating works of the Abee de l'Epee into English.
"Man as a social being has an irresistible propensity to communicate with his species, to receive the ideas of others, and to impart his own conceptions" Green says in the introduction to Vox oculis subjecta. In the first part he surveys the natural capacity of humans for language, quoting extensively from authors such as Holder & Bulwer, before going into a description of how Braidwood's school worked in the second part.