youngest son of Adam Walker (1731-1821), inventor and writer; As a travelling science lecturer, Adam Walker travelled throughout Great Britain and Ireland lecturing on 'natural philosophy'. He was responsible for the introduction of the transparent orrery and an improved model of a harpsichord. His numerous popular works on science included An Epitome of Astronomy. Friend of Joseph Priestley whose discoveries he publicized also, and of other members of the Lunar Society.