atoms of bodies which are equivalent to each other in their ordinary chemical action, have equal quantities of electricity naturally associated with them. "But," he added, "I must confess I am jealous of the term atom: for though it is very easy to talk of atoms, it is very difficult to form a clear idea of their nature, especially when compound bodies are under consideration."
These discoveries and ideas tended to confirm Faraday in preferring, among the rival theories of the voltaic cell, that one to which all his antecedents and connexions predisposed him. The controversy between the supporters of Volta's contact hypothesis on the one hand, and the chemical hypothesis of Davy and Wollaston on the other, had now been carried on for a generation without any very decisive result. In Germany and Italy the contact explanation was generally accepted, under the influence of Christian Heinrich Pfaff, of Kiel (b. 1773, d. 1852), and of Ohm, and, among the younger men, of Gustav Theodor Fechner (b. 1801, d. 1887), of Leipzig,[1] and Stefano Marianini (b. 1790, d. 1866), of Modena. Among French writers De La Rive, of Geneva, was, as we have seen, active in support of the chemical hypothesis; and this side in the dispute had always been favoured by the English philosophers.
There is no doubt that when two different metals are put in contact, a difference of potential is set up between them without any apparent chemical action; but while the contact party regarded this as a direct manifestation of a "contact-force" distinct in kind from all other known forces of nature,
- ↑ Jobanu Christian Poggendorff (b, 1796, d. 1877), of Berlin, for long the editor of the Annalen der Physik, leaned originally to the chemical side, but in 1838 became convinced of the truth of the contact theory, which he afterwards actively defended. Moritz Hermann Jacobi (b.1801, d. 1874), of Dorpat, is also to be mentioned among its advocates.
Faraday's first series of investigations on this subject were made in 1834: Exp. Res., series viii. In 1836 De La Rive followed on the same side with his Recherches sur la Cause de l'Eleels. Voltaique. The views of Faraday and De La Rive were criticized by Pfaff, Recision der Lehre van Galvanismus, Kiel, 1837, and by Fechner, Ann. d. Phys., xlii (1837), p. 481, and xliii (1838), p. 433: translated Phil. Mag., xiii (1838), pp. 208, 367. Faraday returned to the question in 1840, Exp. Res., series xvi and xvii.
