256 On the Excitement of Voltaic Plates. 



The fundamental principle of M. Volta's hypothesis is, that 

 from the coTitact of two metals the equilibrium of electricity is 

 destroyed, and the metals while in contact possess different states 

 of electricity. This principle was supposed to be fairly deduci- 

 ble from the phaenomona of the Voltaic plates. 



In the first place my experiments demonstrate that two platen 

 of dissimilar metals, not previously electrified, being brought 

 into contact, indicate no electricity whatever ; but on being se- 

 parated a change in their electrical state is immediately percep- 

 tible, the one being positive and the other negative. A sup- 

 position that two bodies are in different states of electricity while 

 in contact, because they are so after sepaiation, would certainly 

 be gratuitous ; but to affirm that two bodies, which indicate no 

 electricity whateyer, are in different electrical states, would be 

 nothing less than to contend for an absurdity. In the combina- 

 tion for a Galvanic pile the metals are brought together, they 

 remain in contact a considerable time, and during that time the 

 excitement of the pile commences and continues. How can the 

 excitement which appears in the pile while the metals are in 

 contact, be referred to the same principle that occasions the ex- 

 citement of the plates, which never indicate excitement while 

 in contact — never until they are separated? In the second 

 place, Mr. De Luc has clearly demonstrated that the efficient 

 group consists of two metals, not in contact, but with a moist 

 substance interposed. How then can the excitement be attri- 

 buted to an electro-motive property of metals, exerted while they 

 are in contact, when contact does not appear to be an essential 

 to excitement; — nay, when excitement is not evhiced in the case 

 where contact subsists between the metals, as in dissection the 

 third ; but is fully evident in that, in which contact does not 

 subsist, as in dissection the first ? In the third place the Voltaic 

 plates do not act unless they are ap])lied to each other at so 

 many points as to manifest a sensible cohesion ; but in the 

 couronne de lasses, the porcelain trough, and Mr. De Luc's Jirst 

 dissection of the pile, excitement is produced, although the dif- 

 ferent metals are connected by very little more than a physical 

 point. Again ; the Voltaic plates do not act unless their surfaces 

 be perfectly bright and dry; in the pile the metals, even when 

 new, are never so clean as the Voltaic plates ; in general tliev 

 are very much tarnished, and during their action arc never dry. 

 Is there then any analogy between the circumstances necessary 

 for the excitement of the pile and those necessary for the ex- 

 citement of the Voltaic plates P and how can the phaenomcna 

 of the Voltaic plates afford a first principle for explaining tlic 

 excitement of the Galvanic pile P 



In thus arguing against the hypothesis of M. Volta, I by no 



means 



