HISTORY OF GALVANISM. 1J 



Having thus exhibited a general view of the hypothefis Remarks and 

 which has fuggcfled Itfclf to my mind, as affording a ^f^M*^^ 

 explanation of the phenomena, without offering violence to 

 any of the generally received opinions refpecting chemiftry or 

 electricity, I (hall proceed to illuftrate its truth, by applying 

 it to the explanation of fome of the rood remarkable properties 

 of the pile. It is fufficiently obvious that upon thefe principles 

 the action of the pile will continue as long as the furface of the 

 zinc continues to be oxidated, and that, the fize of the pile re- 

 maining the fame, its energy will be proportionate to the rapi- 

 dity of this operation. The real difference between the two 

 ends of the apparatus will appear to be not fo much a differ- 

 ence in the abfolute quantity of electrical matter contained in 

 them, as a difference in the direction of its current ; becaufe 

 exactly the fame quantity of fluid which paffes out of the zinc 

 end muft be received at the filver end, when a communica- 

 tion is eftablifhed between them. It may be farther remarked, 

 that when the pile is condru&ed as directed by Volta, begin- 

 ning with zinc, then iilver, card and zinc, &c. though the zinc 

 forms the bails of the pile, yet as no change takes place in the 

 electric fluid during its paffage from the filver to the zinc, this 

 might with equal propriety have been called the filver end: in 

 order, however, to avoid confufion, the ufual language has been 

 adopted in this paper ; the terms difcliarging and receiving ends 

 would be more appropriate. 



It has excited a good deal of furprize, that, in the experi-Confiderationa 

 ments of Mr. Davy and Mr. Cruickihank, apparatufes, CO n-°" the r p r para * 

 ffructed of various fliapes and of fuch very different materials, and Cruick- 

 fhould be capable of producing the fame operations. We may fliank * 

 in a few words enumerate the circumftances which are effen- 

 tial to its formation. \ft. An oxidable fubftance, one end or 

 fide of which only is to be oxidated ; Id, A fubftance from 

 which the ele&ric fluid generated during the oxidation can ab- 

 ffracl hidrogen : thefe two fubftances muff be alternately ar- 

 ranged, either perpendicularly or horizontally; the firft fets the 

 fluid at liberty, the fecond confines it and conducts it in the 

 proper direction. When we admit the neceflity of the oxida- 

 tion of the zinc, we immediately fee the reafon why the pile 

 ceafes to act when perfectly pure water is interpofed between 

 the plates, why the action is fufpended in vacuo and increafed 

 by oxigen gas. The hypothefis advanced above fhews us how 



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