1814.] On the Hypotheses of Galvanism. 41 



4. Another objection to the electrical hypothesis is, that it leaves 

 unexplained one of the most important effects attendant upon the 

 action of the pile, the decomposition of the interposed fluid. The 

 fluid is supposed by Volta to act merely as a conductor, and its 

 effect lis a conductor is well illustrated in tlie experiment of De Luc, 

 wheir he states the result of what he calls the third dissection of 

 the pile. The copper and zinc are here in contact with each other, 

 and the moistened card is placed upon the copper ; between this 

 and the next zinc plate is a small wire fr?ime, which prevents the 

 moisture from acting upon the zinc, yet at the same time is sufB- 

 cient for conducting the electricity which is liberafed, because a 

 similar kind of wire is employed for connecting the extremities of 

 the apparatus ; yet in this case no electrical eflects were produced.* 



5. The experiment performed by Sir H. Davy, in which he 

 reversed the action of the pile, by applying difierent fluids to the 

 same metal, has always appeared to me a veiy powerful objection 

 to the electrical hypothesis, and seems originally to have been 

 thought by Sir H. Davy liimself to be decisive against it. If, 

 according to the direct assertion of Volta, fluids differ from each 

 other solely in consequence of their being better or worse con- 

 ductors, it would seem evident that different fluids can produce no 

 difference of effect except in degree : the restoration of the equili- 

 Ijrium may proceed with greater or less rapidity, but the nature of 

 the change tlVected must still remain the same. 



6. According to that modification of the electrical hypothesis, 

 which supposes a progressive increase of power in the apparatus, as 

 we advance from one extremity to the other, (a modification which 

 is absolutely necessary to explain the phenomena,) it follows, that 

 each plate is negative or positive, not merely as respects the con- 

 tiguous plate, but tliat the whole of one end of the pile is negative, 

 and the other positive, while the plates in the centre are in their 

 iiatural state, t lo refer to the numerical illustration, the metals 

 will be as expressed in Fig. 3. 



Fig. 3. 



Z2 



100 



Water 



Z4 



120 



it appears, then, that not only C 1, but also Z 1, is negative; 

 and that not only Z 4, but likewise C 4, is positive; whi|c Z2 and 

 C .'i are l)oth neutral. But the exl'^tence of this stale of things is 

 not coimtcnruiccd by the elfects which we observe to take place : 

 for according to this arrangement it would be impossible for the 

 ajjparaius to act if it were dis|)oscd in a circle ; and it also follows, 

 iliat if we were to break the chain between Z 'J and C 3, we should 



Mill. Jour, jtxvi. 126. 



+ D« Luc, ill Nidi. Jour. .\xvi, 115, Sic. 



