Dulong and Thenard on Platina 95 ? I 345. There can remain no doubt that the property of in- 5 1 ducing combination, which can thus be conferred upon masses r : of platina and other metals by connecting them with the poles 9 \ of the battery, or by cleansing processes either of a mechanical i or chemical nature, is the same as that which was discovered * | by Dobereiner,1 in 1823, to belong in so eminent a degree to ? | spongy platina, and which was afterwards so well experimented j upon and illustrated by MM. Dulong and Thenard,2 in 1823. '* • The latter philosophers even quote experiments in which a 3 very fine platina wire, which had been coiled up and digested in nitric, sulphuric, or muriatic acid, became ignited when put e into a jet of hydrogen gas.3 This effect I can now produce at f pleasure with either wires or plates by the processes described '' (3°6, 337, 341); and by using a smaller plate cut so that it e | shall rest against the glass by a few points, and yet allow the J: water to flow off (fig. 19), the loss of heat is less, the metal is assimilated somewhat to the spongy state, and the probability Q of failure almost entirely removed. . Fig. 19. 346. M. Dobereiner refers the effect entirely to an electric action. He considers the platina and hydrogen as forming a voltaic element of the ordinary kind, in which the hydrogen, I being very highly positive, represents the zinc of the usual •d I arrangement, and like it, therefore, attracts oxygen and combines te j with it.4 *e i 347. In the two excellent experimental papers by MM. Dulong a I and Thenard,5 those philosophers show that elevation of tempera- te | ture favours the action, but does not alter its character; Sir -T ' Humphry Davy's incandescent platina wire being the same | phenomenon with Dobereiner's spongy platina. They show h. that all metals have this power in a greater or smaller degreer ie and that it is even possessed by such bodies as charcoal, >y pumice, porcelain, glass, rock-crystal, etc., when their tempera- )n | tures are raised; and that another of Davy's effects, in which is | oxygen and hydrogen had combined slowly together at a heat >