because it appears insoluble. "I said once to Faraday," wrote Stokes to his father-in-law in 1879, "as I sat beside him at a British Association dinner, that I thought a great step would be made when we should be able to say of electricity that which we say of light, in saying that it consists of undulations. He said to me he thought we were a long way off that yet."[1]
For his next series of researches,[2] Faraday reverted to subjects which had been among the first to attract him as an apprentice attending Davy's lectures: the voltaic pile, and the relations of electricity to chemistry.
It was at this time generally supposed that the decomposition of a solution, through which an electric current is passed, is due primarily to attractive and repellent forces exercised on its molecules by the metallic terminals at which the current enters and leaves the solution. Such forces had been assumed both in the hypothesis of Grothuss and Davy, and in the rival hypothesis of De La Rive;[3] the chief difference between these Being that whereas Grothuss and Davy supposed a chain of decompositions and recompositions in the liquid, De La Rive supposed the molecules adjacent to the terminals to be the only ones decomposed, and attributed to their fragments the power of travelling through the liquid from one terminal to the other.
To test this doctrine of the influence of terminals, Faraday moistened a piece of paper in a saline solution, and supported it in the air on wax, so as to occupy part of the interval between two needle-points which were connected with an electric machine. When the machine was worked, the current was conveyed between the needle-points by way of the moistened paper and the two air-intervals on either side of it; and under these circumstances it was found that the salt underwent decomposition. Since in this case no metallic terminals of any kind were in contact with the solution, it was evident that
