The first account of Volta's pile reached England in a letter to sir Joseph Banks by the inventor (1800). A few weeks,afterwartis Carlisle and Nicholson decomposed water with it, and afterwards several salts. They were the first to use platinum electrodes. Davy, in the same year, traced the electricity of the pile to chemical action. Wollaston (1801) reiterated the same theory, and went the length of attributing even fric tional electricity to chemical action. He proved likewise the identity of the two eleetricities, and showed that by diminishing the electrodes to mere points, the electricity of the machine could produce the same chemical effects as that of the pile. In 1802, improved the construction of the pile by dis posing the plates horizontally in a trough instead of vertically in column. The main'features of electro-chemical decomposition were discussed by Davy in his famous Bakerian lecture of 1806. In 1807, the same philosopher obtained, for the first time by galvanic agency, the metals potassium, Sodium, barium, strontium, calcium, and mag nesium_ Deluc (1809) first made dry piles of gold and silver paper, and these were altered and improved by Zamboni (1812). In 18i3, Davy discovered the electric light, and voltaic arc (see ELECTRIC LIGHT) by means of the colossal battery then placed at his disposal at the royal institution. (Ersted (1820) first observed the action of the cur rent oa the magnetic needle; and, a few-months afterwards, Ampere discovered the law of this action, and originated an electric theory of magnets whielibas proved wonder fully fertile in practical results. In the same year Schweiggcr invented the galvanome ter. In 1825, Becquerel, with the aid of his differential galvanometer, investigated the conductibility of metals. Kemp, in 1826, first used amalgamated zinc for the galvanic. battery. In 1827, Ohm gave a mathematical theory of the pile, rigidly deduced from Volta's fundamental principle, and in perfect keeping with experiment. Faraday
(1831-32) published his discoveries of the induCtion of electric currents, and of the evo lution of electricity from magnets, which have since enriched the science with the induction coil (q.v.) and the magneto-electric machine (q.v.). This distinguished Arician discovered (1833-34) the nature of electrochemical decomposition, and proved that electrochemical and chemical equivalents were identical. In 1836, Daniell .constructed his constant battery. Spenser in England, and Jacobi in Russia, made, sim ultaneously (1837), the discovery of electro-metallurgy. Grove (1839) constructed his nitric-acid battery. Faraday 08-10)gave his proof of the truth of the chemical theory. Smec's battery dates also from this year. In 1843, Wheatstone, by means of his rheo stat and resistance coils, investigated the resistances offered by various conducting sub stances to the current. In the same year Bunsen introduced his carbon battery.
The rivalry between the chemical and contact theorists has favored the advancement of the science, each party calling in the aid of experiment to support their views. Among the more distinguished contact theorists may be mentioned Volta, Ritter, Pfaff, Biot, Deluc, Oinn. and Fechner; and among the chemical theorists, Fabroni, Davy, Wollaston, Parrot., De La Rive, and Faraday. Davy latterly maintained a the ory- of distribution and equilibrium of electricity midway between the two, which num tiered among its supporters Jager, Berzelius, Ermatm, and Prechtl. Recently (1860 onwards), sir William Thomson has given what lie considers to be convincing proofs of Volta's contact theory, but he modifies the theory so far as to make it consistent with the conservation of force.