Should the charge on the sphere be set in motion, then the filaments or lines of force attached to it would also move. Thus far I followed Faraday, but went no farther; if I had gone just a little farther I should have met Maxwell. But, unfortunately for me, this simple picture which I constructed, in order to aid my understanding of Faraday’s “Experimental Researches in Electricity” over which I pondered at Arran, suggested nothing more than a mere geometrical representation of the electrical force which the charged sphere exerts at any point in space. It conveyed no additional information which a simple mathematical formula, well-known at that time, did not convey. Additional information, however, was added by Faraday’s imagination, which introduced here what I and many other mortals at that time considered a strange hypothesis. He described the hypothesis at great length in his books, and here is a brief statement of it: Faraday claimed that all electrical and magnetic actions are transmitted from point to point along his lines of force; and, impelled by a remarkable intuition, he insisted that his lines of force are not mere geometrical pictures but that they had a real physical existence, and that there was something like muscular tension along these lines of force tending to contract them, and a pressure perpendicular to them tending to expand them; and that these tensions and pressures give the same numerical value for the mechanical force between the charges as that calculated from Coulomb’s law, but with the fundamental difference, which Faraday pointed out, that his hypothesis demands a definite finite time for the transmission of electrical and magnetic forces; whereas according to the hypothesis of direct action at a distance, which Coulomb’s law neither favors nor opposes, these forces are transmitted instantaneously. The question of the velocity of transmission of electrical and of magnetic forces through space became, therefore, a crucial question in the decision between the old view and Faraday’s view. In a letter addressed to Maxwell in 1857, and quoted by Campbell, Faraday said: I hope this summer to make some experiments on the time of magnetic action ... that may help the subject on. The time must probably be short as the time of light; but the greatness of the result, if affirmative, makes me not despair. Perhaps I had better have said nothing about it, for I am often long in realizing my intentions, and a failing memory is against me. This letter was written ten years before Faraday’s death, and nothing was ever reported about the result of the experiment planned by him. We know, however, that the result which he expected from the experiment was obtained thirty years later by Hertz, a pupil of Helmholtz. I imagined at Arran that I could hear Faraday say: Where the lines of magnetic force are there is magnetism, and where the lines of electric force are there is electricity.