Disjointed observations connected with animal electricity had been accumulating for many centuries. The first chronicled note that refers to the subject dates back to 676 A. D. Whether or not entirely by chance, the Arabians named the electric eel, or torpedo, in a way that impresses us now as singularly felicitous, raad (the lightning). Toward the end of the last century Redi discovered that the shock was sometimes conveyed through the line and rod to the fisherman, and Kampfer compared the effects to those of electrical discharges. It does not appear, however, that the resemblance was actually believed to be more than accidental until Bancroft urged, in the last ten years of the eighteenth century, the view which was shortly proved. Investigation since has shown that several other aquatic animals possess this astonishing manifestation of vitality, notably the Gymnotus electricus (Surinam eel), the Trichiurus electricus, and the Tetraodon electricus. Humboldt gives an account of wonderful battles in South America between gymnoti and wild horses. In fact, the most expeditious method, if not the most humane one, of capturing these alarming creatures appears to be to drive horses into the pond inhabited by them, and to allow the eels to exhaust their strength by repeated electric discharges before endeavoring to bring them to land by other means.
Cavendish was one of the most noted experimental investigators in the electrical field during the latter third of the eighteenth century. His work was remarkably accurate, considering the lack of a proper equipment for taking observations incident to operations in those days. He computed the relative conductivities of iron and water as four hundred million to unity, and found that the addition of but one part of common salt to one hundred of water increased the conductivity of the latter a hundredfold. A twenty-six-per-cent solution of salt he found to possess only seven and one quarter times the conductivity of the extremely weak one mentioned. He also established the law that the capacity of condensers (of which the previously mentioned Leyden jar is an example) varies directly as the active area, and inversely as the distance separating the conducting surfaces. It was reserved for later investigators to make the grand discoveries which relate to electrochemical dissociation, but Cavendish succeeded in accurately determining the ratio of combination of the elements of water in a method which superficially suggests the inverse of electrolytic decomposition—i. e., by inducing the combination of hydrogen and oxygen by the electric spark in the instrument known as the eudiometer.
Hard on the heels of this work came news of Galvani's remarkable discovery (1790) of the fact that freshly amputated frogs' legs, on being touched along the lines of the muscles by dissimilar metals, were powerfully agitated. We can only speak of this discovery as the stumbling on to an isolated fact, for it was reserved for Volta to establish the generalization that a current is produced in the conductor joining dissimilar metals when the latter are both in contact with a suitable electrolyte (or liquid capable both of conducting electricity and of acting on one, and incidentally also sometimes both, of the metals). Meantime (Du Bois-Reymond observes), "wherever frogs were to be found, and where two different kinds of metal could be procured, everybody was anxious to see the mangled limbs of frogs brought to life in this wonderful way. Physiologists believed that at last they should realize their visions of a vital power, and physicians that no cure was impossible."
Volta first discovered merely the fact of electrification by contact. He wrote to Galvani: "I don't need your frog. Give me two metals and a moist rag, and I will produce your animal electricity. Your frog is nothing but a moist conductor, and in this respect it is inferior to my wet rag!" Nobili, nevertheless, in 1825 proved the existence of galvanic currents in muscles.
Later on Volta invented the "couronne des tasses" (crown of cups), thus at the same time adopting the general form of cell used, with modifications, to-day, and producing the higher electromotive force, or electrical pressure, consequent on the multiplication of the cells in a series battery.
Just before Volta's celebrated communication to the Royal Society, in 1800, Fabroni, of Florence, in discussing Galvani's phenomenon, went to the root of the matter by suggesting that the energy of chemical action was at the bottom of galvanic manifestations, and he was warmly upheld in this contention by Sir Humphry Davy, who, upon the publication of Volta's discoveries, constructed a most elaborate battery with which (apparently about 1806) he produced the arc light between carbon pencils.
In the year referred to, Davy published the results of a series of experiments of enormous significance, among other things of the isolation of the alkali metals, sodium and potassium, whose existence had hitherto not been dreamed of. The simple electrolytic decomposition of water had been accomplished by Nicolson and Carlisle in the last year of the eighteenth century. Sir W. S. Harris says: "A series of new substances was speedily discovered, the existence of which had never before been imagined. Oxygen, chlorine, and acids were all dragged, as it were, to the positive pole, while metals, inflammable bodies, alkalies, and earths became determined to the negative pole of the battery. When wires connected with each extremity of the new battery were tipped with prepared and well-pointed charcoal, and the points brought near each other, then a most intense and pure evolution of light followed, which on separating the points extended to a gorgeous arc." It was at first supposed that the galvanic or voltaic electricity was distinct from the so-called "frictional" or "ordinary" electricity.
A distinguished contemporary of Cavendish was Coulomb, the value of whose work in developing certain exceedingly important mathematical laws with regard to action at a distance, surface densities, and rates of charge dissipation can hardly be overestimated. His name was given to the torsion balance which, since his day, has been the standard instrument for measuring electric and magnetic attractions and repulsions. The importance of his work has since been recognized by the perpetuation of his name in connection with the unit of quantity of electricity, as that of Volta has been honored by its use, abbreviated (volt), to designate the unit of electrical tension or pressure.
Certain highly instructive and interesting data were accumulated about this time by Volta, Laplace, Saussure, and the renowned chemist Lavoisier, in connection with the subject of electrification produced when evaporation, and the liberation of gases and vapors in general from any cause, occurs. The liquid, solid, or mixture liberating the gas was contained in a metallic dish and the resultant electrification of the latter examined qualitatively. Volta's observations led him to conclude that the electrification was always negative, but Saussure demonstrated finally that its sign was dependent on the material of the dish. These experimenters covered, between them all, a somewhat extensive field, examining, among other things, the electrification resulting from the ebullition of various liquids, from the ordinary combustion of fuel, and from the decomposition of acids by metals to liberate hydrogen.