34 On the Hypotheses of Galvanism. [Jan. 



which he employs the most frequently, and which seems to he the 

 only one referred to, or recognized by others, 1 shall speak of this 

 as the electrical hypothesis ; and it will be proper to begin by 

 inciuiring how far the experiments of Bennett, and others of a 

 similar kind, which have been considered as substantiating, or 

 coinciding with it, can be referred to the same principle.* In the 

 iirst pkice, Volta always speaks of the principle as one which he had 

 discovered. In his letter to Cavallo he says, '* Thus I have dis- 

 covered a new law," *' tlie discovery of tliis new law, of this arti- 

 ficial electricity hitherto unknown ;" and afterwards, '•' a new and 

 very singuhr law which I have discovered." Now besides the 

 improbability that Volta would thus disingenuously arrogate" to 

 himself ihe di'^covery of a series of facts to wliich he had no claim, 

 there is a stronger reason for believing that the effects of Bennett's 

 experiments are difi'erent from the action which Volta supposes to 

 take place in his apparatus, although they have been so generally 

 confounded together. Both from the construction of the pile, and 

 from the direct assertion of Volta himself, it api)ears that the metals 

 are in contact when this destruction of their electrical equilibrium 

 takes place ; but in the experiments of Bennett, Cavallo, and others 

 of a similar kind, the metals that act upon each other were either 

 separated, after having been in contact, or were only^ a state of 

 proximity. Bennett never found the different states of + and — 

 to take place while the metals were in contact, but when they were 

 separated, after having been in contact. Fabroni speaks of the 

 effects produced by metals that had been in contact, but were then 

 separated.! Priestley expressly says, that bodies brought near each 

 other acquire different states of electricity; but when they touch, 

 they acquire the same state. % It is upon this principle that the 

 Doubler is formed : metallic plates are put in contact, or are placed 

 very near each other, and are afterwards separated, in order that 

 the effect may be produced. The same remarks may be made upon 

 all experiments of a similar nature ; and it is obvious that it cannot 

 be in this way that the metals act in the pile, because they are kept 

 in contact during the whole of their action. § Yet notwithstanding 

 this circumstance, 1 believe it will be found that all writers have 

 confoundc;d the two principles, or considered them as identical. 



• I (hink. it muit have been obserTed by those who have paid attention to the 

 subject of galvanism, that although Yolta has frequenlly broiiglit forward explana- 

 tions, or illustrations, of his hypothesis, yet that it has never been done in that 

 ample and detailed manner, which might present an unequivocal yiew of it in all 

 its parti aud relations. Thi» may serve as some apology for any unintentional 

 omisiioii or misrepresentation that may be found in this essay; aud will, at the 

 eanie time, accountfor the different modifications of it that have been adopted by 

 different writers. 



+ Jour. Phys. xlix. 350. % History of Electricity, p. 375. 



^ An electrified body may communicate electricity either by contact or by 

 approximation. In the first method the electricity communicated is the same with 

 that of the communicating body ; by the second, the communicated electricity i( 

 of the opposite kind, and is destroyed a; soon as the bodies come into contact. 



