198 Faraday. 



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 

 own. He retained one of the ideas of Grothuss' and Davy's 

 doctrine, namely, that a chain of decompositions and recombi- 

 nations 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 decom- 

 posed 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 



*Exp. lies., 523. 



