Faraday. 203 



Not resting here, however, Koget brought up another argu- 

 ment of far-reaching significance. " If," he wrote,* " there could 

 exist a power having the property ascribed to it by the [contact] 

 hypothesis, namely, that of giving continual impulse to a fluid 

 in one constant direction, without being exhausted by its own 

 action, it would differ essentially from all the other known 

 powers in nature. All the powers and sources of motion, with 

 the operation of which we are acquainted, when producing their 

 peculiar effects, are expended in the same proportion as those 

 effects are produced ; and hence arises the impossibility of 

 obtaining by their agency a perpetual effect ; or, in other words, 

 a perpetual motion. But the electro-motive force ascribed by 

 Yolta to the metals when in contact is a force which, as long 

 as a free course is allowed to the electricity it sets in motion, 

 is never expended, and continues to be exerted with undi- 

 minished power, in the production of a never-ceasing effect. 

 Against the truth of such a supposition the probabilities are 

 all but infinite." 



This principle, which is little less than the doctrine of 

 conservation of energy applied to a voltaic cell, was reasserted 

 by Faraday. The process imagined by the contact school 

 " would," he wrote, "indeed be a creation of 'power -, like no other 

 force in nature." In all known cases energy is not generated, 

 but only transformed. There is no such thing in the world as 

 "a pure creation of force; a production of power without a 

 corresponding exhaustion of something to supply it."f 



As time went on, each of the rival theories of the cell 

 became modified in the direction of the other. The contact 

 party admitted the importance of the surfaces at which the 

 metals are in contact with the liquid, where of course the chief 

 chemical action takes place ; and the chemical party confessed 

 their inability to explain the state of tension which subsists 

 before the circuit is closed, without introducing hypotheses just 

 as uncertain as that of contact force. 



*Roget's Galvanism (1832), 113. 

 t Exp.Res., 2071 (1840). 



