190 EXTRACT FROM "EXPERIMENTAL RESEARCHES." 



tion has heaped up in its own course. This would indeed be 

 a creation of power, and is like no other force in nature. We 

 have many processes by which the form of the power may 

 be so changed that an apparent conversion of the one into 

 the other takes place. So we can change chemical force 

 into electric current, or current into chemical force. The 

 beautiful experiments of Seebeck and Peltier show the con- 

 vertibility of heat and electricity ; and others by Oersted and 

 myself show the convertibility of electricity and magnetism. 

 But in no cases, not even those of the Gymnotus and 

 Torpedo (1790), is there a pure creation of force, a produc. 

 tion of power without a corresponding exhaustion of some- 

 thing to supply it. 2 " 



" 2073. — Were it otherwise than it is, and were the 

 contact theory true, then, as it appears to me, the equality 

 of cause and effect must be denied (2069). Then would 



" - {Note March 2gth, 1840). — I regret that I was not before aware of most 

 important evidence for this philosophical argument, consisting of the opinion 

 of Dr. Roget, given in his Treatise on Galvanism in the Library of Useful 

 Knowledge, the date of which is January, 1829. Dr. Roget is, upon the facts 

 of science, a supporter of the chemical theory of excitation, but the striking 

 passage I desire now to refer to is the following: At §113 of the article 

 Galvanism, speaking of the voltaic theory of contact, he says — 'Were any 

 further reasoning necessary to overthrow it, a forcible argument might be 

 drawn from the following consideration : If there could exist a power having 

 the property ascribed to it by this hypothesis, namely, that of giving a continual 

 impulse to a fluid in a constant direction without being exhausted by its own 

 action it would differ essentially from all 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, through this agency, perpetual motion. But the electromotive force 

 ascribed by Volta to the metals 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 excited with undiminished power in the production of a never-ceasing 

 effect. Against the truth of such a supposition, the probabilities are all but 

 infinite. ' — Roget." 



