Conducting Power of Solid and Liquid Bodies. 335 



contact respectively with the polarized platinum plates. It is 

 true that on the cessation of the polarizing current the polarized 

 electrodes are capable of generating a reverse current, but that 

 only results from the continued action of the same affinities 

 which have to be dissolved by the primary current, either in the 

 case of the polarized electrodes or the hypothetical neutral ones. 



The principle we would venture to suggest for estimating the 

 resistance to transit in any case may be stated thus. Each of the 

 affinities concerned, viz., those dissolved or those satisfied, may 

 be considered equivalent to a definite electro-motive force; let 

 the sum of such forces belonging to the affinities dissolved be 

 represented by F, and of those belonging to the affinities satisfied 

 by F'; all affinities that do not take effect, either in the separation 

 or the combination of elements being neglected, and including 

 under the term affinity all attractions that are capable of modify- 

 ing the form or chemical action of a body, attributing also a defi- 

 nite force to the catalytic action of the electrode in facilitating 

 the evolution of the element when that takes place, — then repre- 

 senting the resistance to transit by E, we have E = F — F'. 



We are not aware indeed that any systematic experiments have 

 been made to demonstrate this principle ; but we think it suffi- 

 ciently probable in the present state of our knowledge on the sub- 

 ject. We have seen something like this hinted at by some 

 authors, but do not recollect to have seen it definitely laid down. 



In the first experiment noticed by the author under the present 

 head, the current was passed through a solution of sulphate of 

 copper and positive electrode of copper and negative of platinum. 

 The resistance to transit being accurately measured apart from 

 the resistance to conduction, proved to be actually null or at least 

 within the probable errors of experiment. Here the affinities 

 dissolved on one side are satisfied on the other, reproducing, so 

 for as we know, precisely the same state of things, so that 



F-F-E-0. 



Mr. Smee mentions a curious circumstance respecting the action 

 of compound batteries that very beautifully illustrates the same 

 lhi ng. If the exciting acid of one pair of the series be saturated 

 with the zinc before that of the other pairs, the solution of the 

 salt of zinc in that pair is electrolyzed and the zinc deposited on 

 the negative plate, and this process extends from pair to pair of a 

 series of twelve or more until the zinc is deposited on the neg- 

 ate plate of every pair except one, the action remaining in the 

 fest pair being sufficient to decompose the salt of zinc with zinc 



electrodes in all the other pairs. 



hi cases where gases were evolved from one or both electrodes, 

 the general result obtained by the author is, that the apparent 

 distance to transit, i. e., all resistance over and above the simple 

 resistance to conduction due to the liquid and other parts of the 



