HISTORY OF GALVANISM,
OR
VOLTAIC ELECTRICITY.
Percusssæ gelido trepidant sub pectore fibræ,
Et nova desuetis subrepens vita medullis
Miscetur morti: tunc omnis palpitat artus
Tenduntur nervi; nec se tellure cadaver
Paullatim per membra levat; terrâque repulsum est
Erectumque simul.
Lucan. vi. 752.
The form which lay before inert and dead,
Sudden a piercing thrill of change o’erspread;
Returning life gleams in the stony face,
The fibres quiver and the sinews brace,
Move the stiff limbs;—nor did the body rise
With tempered strength which genial life supplies,
But upright starting, its full stature held,
As though the earth the supine corse repelled.
CHAPTER I.
Discovery of Voltaic Electricity.
WE have given the name of mechanico-chemical to the class of sciences now under our consideration; for these sciences are concerned with cases in which mechanical effects, that is, attractions and repulsions, are produced; while the conditions under which these effects occur, depend, as we shall hereafter see, on chemical relations. In that branch of these sciences which we have just treated of, Magnetism, the mechanical phenomena were obvious, but their connexion with chemical causes was by no means apparent, and, indeed, has not yet come under our notice.
The subject to which we now proceed, Galvanism, belongs to the same group, but, at first sight, exhibits only the other, the chemical, portion of the features of the class; for the connexion of galvanic phenomena with chemical action was soon made out, but the mechanical effects which accompany them were not examined till the examination was required by a new train of discovery. It is to be observed, that I do not include in the class of mechanical effects the convulsive motions in the limbs of animals which are occasioned by galvanic action; for these movements are produced, not by attraction and repulsion, but by muscular irritability; and though they indicate the existence of a peculiar agency, cannot be used to measure its intensity and law.
The various examples of the class of agents which we here consider,—magnetism, electricity, galvanism, electro-magnetism, thermo-electricity,—differ from each other principally in the circumstances by which they are called into action; and these differences are in reality of a chemical nature, and will have to be considered when we come to treat of the inductive steps by which the general principles of chemical theory are established. In the present part of our task, therefore, we must take for granted the chemical conditions on which the excitation of these various kinds of action depends, and trace the history of the discovery of their mechanical laws only. This rule will much abridge the account we have here to give of the progress of discovery in the provinces to which I have just referred. [238]
The first step in this career of discovery was that made by Galvani, Professor of Anatomy at Bologna. In 1790, electricity, as an experimental science, was nearly stationary. The impulse given to its progress by the splendid phenomena of the Leyden phial had almost died away; Coulomb was employed in systematizing the theory of the electric fluid, as shown by its statical effects; but in all the other parts of the subject, no great principle or new result had for some time been detected. The first announcement of Galvani’s discovery in 1791 excited great notice, for it was given forth as a manifestation of electricity under a new and remarkable character; namely, as residing in the muscles of animals.[1] The limbs of a dissected frog were observed to move, when touched with pieces of two different metals; the agent which produced these motions was conceived to be identified with electricity, and was termed animal electricity; and Galvani’s experiments were repeated, with various modifications, in all parts of Europe, exciting much curiosity, and giving rise to many speculations.