250 HISTORY OF GALVANISM. 



the equal reaction which necessarily accompanies this action acts op- 

 positely to the action, not in the same line, but in a parallel line, a1 

 the other extremity of the distance ; thus forming a primitive couple 

 to use a technical expression borrowed from mechanics. To this 

 Ampere objected, 4 that the direct opposition of all elementary action 

 and reaction was a universal and necessary mechanical law. He 

 showed too that such a couple as had been assumed, would follow as 

 A derivative result from his theory. And in comparing his own the- 

 ory with that in which the voltaic wire is assimilated to a collection 

 of transverse magnets, he was also able to prove that no such assem- 

 blage of forces acting to and from fixed points, as the forces of mag- 

 nets do act, could produce a continued motion like that discovered by 

 Faraday. This, indeed, was only the well-known demonstration of 

 the impossibility of a perpetual motion. If, instead of a collection of 

 magnets, the adverse theorists had spoken of a magnetic current, they 

 might probably interpret their expressions so as to explain the facts ; 

 that is, if they considered every element of such a current as a mag- 

 net, and consequently, every point of it as being a north and a south 

 point at the same instant. But to introduce such a conception of a 

 magnetic current was to abandon all the laws of mao-netic action 



o o 



hitherto established ; and consequently to lose all that gave the hypo- 

 thesis its value. The idea of an electric current, on the other hand, 

 was so far from being a new and hazardous assumption, that it had 

 already been forced upon philosophers from the time of Volta ; and 

 in this current, the relation of preceding and succeeding, which neces- 

 sarily existed between the extremities of any element, introduced that 

 relative polarity on which the success of the explanations of the facts 

 depended. And thus in this controversy, the theory of Ampere has a 

 great and undeniable superiority over the rival hypotheses. 



1 



CHAPTER VII. 



CONSEQUENCES OF THE ELECTRODYNAMIC THEORY. 



T is not necessary to state the various applications which were soon 

 made of the electro-magnetic discoveries. But we may notice one 



* Ampere, Thiorie, p. 154. 



