be made up of particles, or to be indefinitely divisible, is not usually stated, though Franklin himself certainly believed in the existence of an electrical particle or atom, for he says: "The electrical matter consists of particles extremely subtle, since it can permeate common matter, even the densest, with such freedom and ease as not to receive any appreciable resistance." When Franklin wrote that, however, he could scarcely have dreamed that it would ever be possible to isolate and study by itself one of the ultimate particles of the electrical fluid. The atomic theory of electricity was to him a pure speculation.
The first bit of experimental evidence which appeared in its favor came in 1833, when Faraday found that the passage of a given quantity of electricity through a solution containing a compound of hydrogen, for example, would always cause the appearance at the negative terminal of the same amount of hydrogen gas, irrespective of the kind of hydrogen compound which had been dissolved, and irrespective also of the strength of the solution; that, further the quantity of electricity required to cause the appearance of one gram of hydrogen, would always deposit from a solution containing silver exactly 107.1 grams of silver. This meant, since the weight of the silver atom is exactly 107.1 times the weight of the hydrogen atom, that the hydrogen atom and the silver atom are associated in the solution with exactly the same quantity of electricity. When it was further found in this way that all atoms which are univalent in chemistry, that is, which combine with one atom of hydrogen, carry precisely the same quantity of electricity, and all atoms which are bi-valent carry twice this amount, and, in general, that valency, in chemistry, is always exactly proportional to the quantity of electricity carried by the atom in question, it was obvious that the atomic theory of electricity had been given very strong support.
But striking and significant as were these discoveries, they did not serve to establish the atomic hypothesis. Indeed, the attention which Faraday himself directed to the rôle played by the medium which surrounded a body carrying a charge, or the wire through which a charge was passing (an electric current) led to a point of view which was distinctly antagonistic to the atomic concept of electricity. This point of view was emphasized very strongly by the followers of Maxwell, notably by Oliver Lodge, who through his book on "Modern Views of Electricity" influenced very largely the points of view adopted by the text-books of the last two decades of the nineteenth century. This view was that an electric charge is nothing more than a "state of strain in the ether," and an electric current, instead of representing the passage of anything definite along the wire, corresponded merely to a continuous "slip" or "breakdown of a strain" in the medium within the wire, whatever these terms may mean. Now there can be no doubt that
