1. du Bois-Reymond Emil , op. cit. (87), p. 51.
2. ‘Study and Research’, Annual Report of the Smithsonian Institution (1894), p. 661, p. 660, and pp. 662–63, resp.
3. Rather , op. cit. (23), pp. 43 and p. 45, resp.
4. McCormmach , op. cit. (1), pp. 159–65.