Page:A history of the theories of aether and electricity. Whittacker E.T. (1910).pdf/218

 all hypotheses which attributed decomposition to the action of the terminals were untenable.

The ground being thus cleared by the demolition of previous theories, Faraday was at liberty to construct a theory of his He retained one of the ideas of Grothuss' and Davy's doctrine, namely, that a chain of decompositions and recombinations takes place in the liquid; but these molecular processes he attributed not to any action of the terminals, but to a power possessed by the electric current itself, at all places in its course through the solution. If as an example we consider neighbouring molecules A, B, C, D, ... of the compound—say water, which was at that time believed to be directly decomposed by the current—Faraday supposed that before the passage of the current the hydrogen of A would be in close union with the oxygen of A, and also in a less close relation with the oxygen atoms of B, C, D, ...: these latter relations being conjectured to be the cause of the attraction of aggregation in solids and fluids. When an electric current is sent through the liquid, the affinity of the hydrogen of A for the oxygen of B is strengthened, if A and B lie along the direction of the current; while the hydrogen of A withdraws some of its bonds from the oxygen of A, with which it is at the moment combined. So long as the hydrogen and oxygen of A remain in association, the state thus induced is merely one of polarization; but the compound molecule is unable to stand the strain thus imposed on it, and the hydrogen and oxygen of A part company from each other, Thus decompositions take place, followed by recombinations: with the result that after each exchange an oxygen atom associates itself with a partner nearer to the positive terminal, while a hydrogen atom associates with a partner nearer to the negative terminal.

This theory explains why, in all ordinary cases, the evolved substances appear only at the terminals; for the terminals are the limiting surfaces of the decomposing substance; and, except. at them, every particle finds other particles having a contrary