406 Mr. J. A. Fleming on the new 



a 



4. When the two plates in one electrolyte are joined by a 

 wire, or when simple cells are joined up in series and the circuit 

 closed by a wire, we find it stated that there is a constant sepa- 

 ration of the electricities at the point of contact of different 

 metals and a constant recombination, attended with decomposi- 

 tion, through the electrolyte. tl Perhaps it is strictly accurate 

 to say that the difference of potential is produced by the contact, 

 and that the current which is maintained by it is produced by 

 chemical action" *. And, lastly, that in a series of cells the 

 electromotive force is due to the sum of the differences of poten- 

 tial produced by all the contacts. 



The above quotations may be taken as affording the plainest 

 notion of the new contact theory ; and it will be seen that its fun- 

 damental propositions are briefly these : — 



I. That two plates of different metals in one liquid are at the 

 same potential when insulated and separated; i. e. there is no 

 difference of potential due to chemical affinity. 



II. In a cell series the gradual rise in potential, or the electro- 

 motive force, is due only to the dissimilar metallic contacts. 



III. The chemical action in the battery is the result rather 

 than the cause of the difference of potential, and is looked upon 

 as an accompanying action rather than as the actual creator of 

 the current, it having little or nO share in the production of the 

 difference of potential between the terminals. 



These are, I venture to think, points not to be admitted as 

 proved without further inquiry, and against which, as I shall 

 hope to show, some grave if not insuperable objections may be 

 urged, founded on other experimental evidence. 



The first question to be settled is, then, whether in a series 

 of cells the whole of the difference of potential between the ter- 

 minals is due to the contacts, as above stated, or whether any 

 portion is due to the tendency towards chemical combination 

 existing between the metals and the electrolytes ; and, as a con- 

 sequence, whether in a single cell the plates are at the same 

 potential or at different potentials, owing to the difference of 

 chemical action upon them. Now I think this point will be 

 sufficiently proved if we can establish by experiment, (i) that a 

 battery of cells can be constructed without any dissimilar me- 

 tallic contacts and with terminal plates of the same metal, and 



electrochemical one ; but various causes may interfere to disturb it. At 

 any rate it is sufficient to show that this fact of the partial identity of the 

 potential series for different acids cannot by any means be claimed as con- 

 clusive of the contact theory. Moreover, although the order may be the 

 same for the different liquids, we do not know that the coefficients are the 

 same for each metal in every dilute acid. 

 * Electricity and Magnetism, pp. 53-55. 



