From 1857, W. W. Baxter of Bromley was CD’s regular chemist. The date is established from references to buying photography supplies for William Erasmus Darwin in CD’s Classed accounts (Down House MS). CD spent £9 5s. on ‘Photography’ on 23 July 1857, and £2 15s. on ‘Photography for William’ on 28 December 1857. (These particular payments were unlikely to have been to Baxter, however; CD paid Baxter’s bill annually, in January (CD’s Account books–cash account).)