this pressure to be exerted by some external elastic medium which was itself thrown into a state of stress by the reaction of the com pressed electric fluid.
Apparently the first physicist to definitely suggest the pressure of an elastic medium as the cause of electric attractions and repulsions was Dr. Thomas Young. In his lectures which were given before the Royal Institution and published in 1807 he says:
It must be confessed that the whole science of electricity is yet in a very imperfect state. We know little or nothing of the intimate nature of the substances and actions concerned in it: and we can never foresee, without previous experiment, where or how it will be excited. We are wholly ignorant of the constitution of bodies, by which they become possessed of different conducting powers; and we have only been able to draw some general conclusions respecting the disposition and equilibrium of the supposed electric fluid from the laws of the attractions and repulsions that it appears to exert. There seems to be some reason to suspect from the phenomena of cohesion and repulsion that the pressure of an elastic medium is concerned in the origin of these forces; and if such a medium really exists, it is perhaps nearly related to the electric fluid.
Between the time of Cavendish's writing and the publication of Young's lectures there had been great advancement in electrical knowledge and very important improvement in facilities for electrical measurement. The most important discovery in electrostatics was Bennett's discovery of contact electrical charges. Galvani's discovery of muscular contractions due to electrical stimulation of the nerves had attracted a great deal of attention, and there was much controversy over the question whether the force with which Galvani was experimenting was really electrical, or whether it was some force before unknown and which was called Galvanism. This question was finally settled by Volta, who in 1796 discovered the electrical current set up in a circuit containing two metals and an electrolytic conductor. Then in 1800 Volta announced the discovery of the voltaic pile, by means of which the electromotive force of a single metallic pair could be increased to any desired degree. This was followed the same year by the discovery by Carlisle and Nicholson of the separation of water by electrolysis and very rapidly thereafter by the experiments of Davy and others on electrolytic dissociation. As a result of these investigations, the study of electrostatic phenomena was neglected, and aside from the work of Faraday but little of consequence has since been done in this field.
Faraday's most important contributions to electrostatics were his proofs of the perfect equality of the inducing and induced charges in all cases; his proof that electric induction might sometimes act in curved lines (as he stated it) and hence could not be
