Voltaic BatterieSi 8fc, 69 



The arrangement of the experiments which is here adopted is 

 very nearly the same in the order of succession as that in 

 which they were made, and differs from that order only so far 

 as has appeared desirable, in order the more clearly to show 

 the results actually arrived at, and at the same time to indi- 

 cate progressively the evidence for other results anticipated, 

 but the completion of which can be reached only at a more 

 advanced stage, or at the conclusion of the whole inquiry. 

 You will permit me also to refer to the circumstance, that 

 occasionally throughout the statements which follow I have 

 thought it desirable to make explicit and repeated references 

 to many minute and well-known details involved in researches 

 of this nature, which in writing to one with whom the subject 

 is so familiar, and to whom each particular would be sug- 

 gested by the matter in immediate connexion, may appear to 

 be somewhat unnecessary^ But as I am aware that my paper 

 may not be confined to your own perusal, I have preferred to 

 aid any demonstrations it may attempt by a recurrence to 

 such details, made explicitly and wherever they might appear 

 useful, rather than, for the sake of inserting only that which 

 is perfectly novel, to omit them, and thus lose the advan- 

 tage of as much clearness in description as the nature of 

 the subject itself might otherwise admit of. 



Section II. — The Principle of Investigation. 



20. The principle employed throughout the following in- 

 vestigation to detect and estimate effects, has arisen out of 

 the discovery of Faraday of the definite character of voltaic 

 action. 



21. The experiments which served chiefly, in the hands of 

 its discoverer, to establish this great principle, were those in 

 which a current of electricity, evolved by a compound arrange- 

 ment, was passed through water, when it was found, first, that 

 the water which such a current decomposed, bore, in its quan- 

 tity, a definite relation to the quantity of the elements by whose 

 mutual action that current was produced ; and, secondly, that 

 the quantity of any other body than water, which the same 

 current decomposed, was likewise definite, and bore a fixed 

 relation both to the quantity of water first decomposed and 

 to the quantity of elements expended in any one cell of the 

 generating battery itself. And the relations thus presented 

 were found to be exactly the same as the relations between 

 the different respective chemical equivalent numbers of the 

 bodies engaged in the operations. So that, for example, in 

 the instances of the zinc expended in any one cell of the bat- 



