Eloge of Alexander Volta. 19 



Among the numerous facts which this celebrated school op- 

 posed to Volta, there is one so singular as to throw us for a 

 moment into a state of suspense, — I mean the convulsions which 

 Galvani produced by touching the muscles of a frog with two 

 plates, not of different kinds, as Volta believed necessary, but 

 both taken from the same piece of metal. This effect, although 

 it was not constant, presents in appearance an insurmountable 

 objection to the new theory. 



Volta replied, that the plates employed by his opponents 

 might be identical in the name they bore, and even in their che- 

 mical nature, and yet differ in other circumstances, so as to pos- 

 sess properties truly distinct. In his hands, indeed, the plates, 

 although composed of two contiguous portions of the same piece 

 of metal, acquired a certain power when they had changed their 

 temperature, degree of nealing, or even the polish of one of their 

 elements. 



This discussion, therefore, did not invalidate the theory of the 

 celebrated professor. It proved only that the word dissimilar^ 

 applied to two superimposed metallic elements, had been under- 

 stood in relation to electrical phenomena in too restricted a 

 sense. 



Volta had to sustain another and a more severe assault. l)r 

 Valli, his antagonist, had produced convulsions simply by the 

 touch of two different parts of the frog, without the use of me- 

 tal, which, in all analogous experiments, had been, according to 

 our associate, the principal generator of electricity. 



It may be perceived, from more than one passage in Volta's 

 letters, how much he was hurt by the tone of assurance with 

 which the galvanists, old and young (I use his own expressions), 

 boasted of having reduced him to silence. This silence, at all 

 events, did not long continue. An attentive examination of 

 Valli's experiments soon convinced Volta that there were two 

 conditions necessary to secure success,-*as great a heterogeneity 

 as possible between the organs of the animal brought into con- 

 tact, and the interposition of a third substance between these 

 organs. The fundamental principle of the Voltaic theory, in- 

 stead of being endangered, thus acquired additional extension. 

 The metals no longer formed a class by themselves, and analogy 

 led to the belief that two dissimilar substances, of what nature 



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