70 °N THE THEORY OF GALVANISM. 



cither apparatus at pleafure every effect of galvanifm ftrictly 

 But electricity f ca j| et ^ or f electricity. There appears however to be a 

 the pile. great difference in their mode of action ; in the pile the fluid 



is actually generated, whereas in the machine it is merely 

 transferred from one body, where it previoufly exifted in a 

 difengaged ftate, to another body. In fupport of this pofition 

 it may be alledged, that the energy of the pile is found to be 

 materially increafed by being infulated, whereas in the com- 

 mon machine it is impoffible to produce any confiderable de- 

 gree of excitement *, unlefs there be a communication formed 

 by a conductor between the rubber and the furface of the earth. 

 Dr. Woollaflon, who has thrown fo much light upon this fub- 

 ject, feems to have carried too far the analogy between the 

 methods of exciting the electric fluid, when he confiders the 

 The pile is con- oxidation of the amalgam on the cufhion, as more than a fe T 

 rating: and^hc'" con dary caufe in the operation of the electrical machine. By 

 ele&ric machine confideiing the pile as a generating, and the other as only a 

 apparatuf"^ collecling apparatus, we may aflign a probable caufe for the 

 vivid fparks, the bright flafhes, and the more confiderable 

 marks of excitement which are exhibited by the common ma- 

 chine ; in this latter cafe a quantity of electric fluid derived 

 from the neighbouring bodies, is as it were forcibly detained 

 in the apparatus, and is ready to efcape to every fubftance 

 for which it poffeffes any degree of affinity ; whereas in the 

 pile, though there is a rapid and conftant production of elec- 

 tricity, yet being derived from a change which takes place in 

 its own eompofition, by which different parts of it appear to 

 acquire different capacities for the electric fluid, it feems little 

 difpofed to enter into any combination with the furrounding 

 bodies, and is only brought into action by the approximation 

 of the different parts of the apparatus itfelf. 

 Theeffeasof It wasjuftly remarked by Mr. Nicholfon, that the peculiar 



the pile :has been e ff e $ s () f tne pile may be afcribed to the electric fluid exifting 

 afenbed to its . . . , r ' . . , , r . n ° 



great quantity of m it in a large quantity, but at a low degree of mteniity. 



elea.ricity a * * This confideration eafily explains all the lingular properties of 



1 y ' the apparatus, but it ftill remains to be afcertained by what 



* This is an overfight. In fact, the ground ferves only to form 

 a communication between the receiving conductor and the cufhion, 

 and the excitation is fully as ftrong when the current is made to fly 

 from the plus to the minus conductor, when both are infulated.- --N. 



means 



