GALVANISM is that branch of the science of electricity which treats of the electric currents arising from chemical action, more particularly from that attending the dis solution of metals. It is sometimes called dynamical electricity, because it deals with current electricity, or electricity in motion, and it thus distinguished from frictional electricity (q.v.), which is called statical in consequence of its investigating the electric condition of bodies in which electricity remains insulated or stationary. These terms, although in the main thus properly applied, are in all strictness applicable to both sci ences. Frictional electricity, though small in quantity, can pass in a sensible current, and galvanic electricity, though small in tension, can be made to manifest the attractions and repulsions of stationary electricity Thus the series of discharges which are trans mitted in a wire connecting the prime donduotor of a machine in action with the ground, possesses, though feebly, the characteristics of a galvanic current; and the insulated poles of a ninny-celled galvanic battery, manifest before the current begins the electric tension of the friction machine. The other branches of current electricity will be found under INDUCTION OF ELECTRIC CURRENTS, MAGNETO-ELECTRICITY, and THERMO ELECTRICITY.
Historical Sketch.—The science of G. dates from the close of the 18th century. In the year 1780, Galvani, in making investigations on the nervous irrittibility of cold blooded animals, discovered by accident that the limbs of a recently killed frog, when hung by the crnral nerve on a metal support near an electric machine, contracted con vulsively at the recurrence of each spark. This he properly accounted for by the back stroke. See ELECTRICITY, Six years afterwards (1786), in experimenting ou atmos pheric electricity with frog limbs as delicate electroscopes, he obtained, also accident ally. the same convulsions by bringing the copper hook on which the nerve hung, and the limb itself, simultaneously iu contact with an iron railing. The similarity of the result led, him to attribute it to the same cause—viz., electricity either existing in the limb itself or produced in the conducting arc of metal. On consideration; he adopted the former hypothesis. and looked upon the limb a sa self-charging Leyden jar, with the nerve as the brass knob and wire, the interior of the muscle as the inner coating, its exterior the outer coating, and the metal arc as the discharging tongs. See ELECTRICITY,
AxiliAL. He first published his researches in 1791. Volta, 1792, discarded the account given by Galvani of his experiment; and from the fact that the convulsions in question took place with more energy when there were two metals in the conducting are instead of one, attributed the source of electricity to the heterogeneity of the metals employed. He maintained that at the surface of contact of two different metals an electric force arising from their heterogeneity is generated, which throws them into different tensions. This doctrine forms the fundamental principle of the contact theory of galvanism. In reply to Volta, Galvani proved incontestably that the contraction in the limbs of the frog took place when only one metal was employed, and even when the conductor was not of metal at all. Subsequent discovery has proved Galvani to be partly right in attributing the cause of these convulsions to animal electricity, and Volta also to be partly right in attributing them to generated in the metal arc, for both causes may be at work in producing the result. Volta's theory of contact is still maintained, though another theory obtains less support which attributes the source of galvanic electricity to the chemical action 0e a thinkd on a metal coupled with another metal less easily acted on than itself. Fabron., a professor at Florence, was the first (1792) to sug gest chemical action as one of the causes at work in Galvani's experiment. Volta did not accept of Galvani's vindication, but theory. by several apparently con elusive experiments. In 1799, he constructed, as the crowning evidence of the truth of his reasoning, his pile, and with it properly begins the history of galvanism. To Gal vani is thus due the merit of discovering a new manifestation of electricity; to Volta is due the merit of displaying in it a source of power of incalculable importance, and which,' but for his genius, might have remained among the barren .curiosities of science. Hence it becomes a question of some difficulty to decide to which of the two the science we are discussing owes its origin—whether it is to be called Galvanism or Voltaism. Priority of discovery has led men generally to decide in favor of Galvani, although Volta has almost equal claim to have his name attached to the science.