“I propose, then, first to describe a method by which the motion of such a fluid can be clearly conceived; secondly to trace the consequences of assuming certain conditions of motion, and to point out the application of the method to some of the less complicated phenomena of electricity, magnetism, and galvanism; and lastly, to show how by an extension of these methods, and the introduction of another idea due to Faraday, the laws of the attractions and inductive actions of magnets and currents may be clearly conceived, without making any assumptions as to the physical nature of electricity, or adding anything to that which has been already proved by experiment. “By referring everything to the purely geometrical idea of the motion of an imaginary fluid, I hope to attain generality and precision, and to avoid the dangers arising from a premature theory professing to explain the cause of the phenomena. If the results of mere speculation which I have collected are found to be of any use to experimental philosophers, in arranging and interpreting their results, they will have served their purpose, and a mature theory, in which physical facts will be physically explained, will be formed by those who by interrogating Nature herself can obtain the only true solution of the questions which the mathematical theory suggests.” The idea was a bold one: for a youth of twenty-three to explain, by means of the motions of an incompressible fluid, some of the less complicated phenomena of electricity and magnetism, to show how the laws of the attractions of magnets and currents may be clearly conceived without making any assumption as to the physical nature of electricity, or adding anything to that which has already been proved by experiment. It may be useful to review in a very few words the position of electrical theory[57] in 1855. Coulomb’s experiments had established the fundamental facts of electrostatic attraction and repulsion, and Coulomb himself, about 1785, had stated a theory based on these experiments which could “only be attacked by proving his experimental results to be inaccurate.”[58] Coulomb supposes the existence of two electric fluids, the theory developed previously by Franklin, but says-- “Je préviens pour mettre la théorie qui va suivre à l’abri de toute dispute systématique, que dans la supposition de deux fluides électriques, je n’ai autre intention que de présenter avec le moins d’éléments possible les résultats du calcul et de l’expérience, et non d’indiquer les véritables causes de l’électricité.” Cavendish was working in England about the same time as Coulomb, but he published very little, and the value and importance of his work was not recognised until the appearance in 1879 of the “Electrical Researches of Henry Cavendish,” edited by Clerk Maxwell.