20 Wilde Lecture, Nature, March 12, 1908; ibid. Sept. 6, 1900, p. 485; Aether and Matter, p. 288. Cf. also Lord Kelvin, Fortnightly Review, 1892, p. 313.

21 Joly, The Abundance of Life, Proc. Roy. Dublin Soc. VII, 1890; and in Scientific Essays, etc. 1915, p. 60 et seq.

22 Papillon, Histoire de la philosophie moderne, I, p. 300.

23 With the special and important properties of colloidal matter we are, for the time being, not concerned.

24 Cf. Hans Przibram, Anwendung elementarer Mathematik auf Biologische Probleme (in Roux〙s VortrûÊge, Heft III), Leipzig, 1908, p. 10.

25 The subject is treated from an engineering point of view by Prof. James Thomson, Comparisons of Similar Structures as to Elasticity, Strength, and Stability, Trans. Inst. Engineers, Scotland, 1876 (Collected Papers, 1912, pp. 361〓372), and by Prof. A. Barr, ibid. 1899; see also Rayleigh, Nature, April 22, 1915.

26 Cf. Spencer, The Form of the Earth, etc., Phil. Mag. XXX, pp. 194〓6, 1847; also Principles of Biology, pt. II, ch. I, 1864 (p. 123, etc.).

27 George Louis Lesage (1724〓1803), well known as the author of one of the few attempts to explain gravitation. (Cf. Leray, Constitution de la Matiû´re, 1869; Kelvin, Proc. R. S. E. VII, p. 577, 1872, etc.; Clerk Maxwell, Phil. Trans. vol. 157, p. 50, 1867; art. 〜Atom,〝 Encycl. Brit. 1875, p. 46.)

28 Cf. Pierre Prûˋvost, Notices de la vie et des ûˋcrits de Lesage, 1805; quoted by Janet, Causes Finales, app. III.

29 Discorsi e Dimostrazioni matematiche, intorno û  due nuove scienze, attenenti alla Mecanica, ed ai Movimenti Locali: appresso gli Elzevirii, MDCXXXVIII. Opere, ed. Favaro, VIII, p. 169 seq. Transl. by Henry Crew and A. de Salvio, 1914, p. 130, etc. See Nature, June 17, 1915.