[Feb. 



86 On the Hijpolheses of Galvavism. 



city is liberated, wliich 



is transmitted to the sc- Fig. 4. 



cond copper plate, and 



which raises it to 120°. 



{Fig. 4.) According to 



the chemical hypo- 

 thesis, although one end of the pile becomes highly positive, and 

 is therefore disposed to communicate a portion of its redundant 

 electricity to the otiier end, yet this end may be considered as only 

 relatively negative, and there is no part of the apparatus in a neu- 

 tral state. There is no tendency in any part of the apparatus to 

 restore the equilibrium of the electric fluid, which is destroyed by 

 the oxidation of the metal. The sole effect is to increase the elec- 

 tricity of one end of the apparati;s ; and tlierefore the more power- 

 ful is the action of the fluid, either in oxidating the metals, or in 

 conveying the electricity to the opposite surface, the more powerful 

 will be the effect of the apparatus. This effect does not necessarily 

 depend upon the ends of the pile being united, because the essence 

 of the operation eTinsists in the oxidation of one of the inetals. It 

 is, however, to be expected, that the effect will be increased when 

 the extremities of the pile are united ; for in this case the electricity 

 will be powerfully attracted towards one end of the apparatus, in 

 order to produce an equilibrium with the other end, which is rela- 

 tively negative. The chemical hypothesis is not encumbered with 

 the necessity of a current of electricity from one end of the pile to 

 the other ; it only supposes the passage of the electricity across the 

 interposed fluid in each individual pair of metals. The chemical 

 differs from the electrical hypothesis in the material circumstance 

 of the former pointing out a source for the liberation or evolution 

 of electricity, in consequence of a change in the nature of one of 

 the substances, which renders it less disposed than before to contain 

 it. The electrical hypothesis only contemplates an interchange of 

 electricity between the different parts of the apparatus, one part 

 losing a poitiua merely in consequence of the other part attracting 

 It, a process by vi'hich there can be no absolute production of elec- 

 tricity. The chemical differs from the -electrical hypothesis with 

 respect to the state of the contiguous metals : the electrical hypo- 

 thesis supposes ihat they can have different states of electricity 

 while in contact ; the chemical takes it for granted that while they 

 are in contact their electrical states must be similar. The chemical 

 hypothesis explains all the facts that have been observed respecting 

 the necessity of oxygen for the action of the apparatus, it explains 

 the reason why the metals must ditferin their degree of oxidability, 

 and why the fluid must be one which will act diflercntly upon the 

 two metals. The facts which have been noticed respecting the dif- 

 ferent effects of the interposed fluids may be explained by referring 

 to three^ circumstances, which all coincide with the chemical 

 hypothesis. 1. That the fluid acts only upon one of the metals. 

 2- That the surface of one of the metals only is oxidated with a 



