EXPERIMENT. 29 



which previous experimenters had thought essential for 

 the production of electrical phenomena. Davy asserted 

 that- no known fluids, except such as contain water, could 

 be made the medium of connexion between the poles of a 

 battery ; and some chemists believed that water was an 

 essential agent in electro-chemical decomposition. Faraday 

 gives abundant experiments to show that other fluids 

 allow of electrolysis, and attributes the erroneous opinion 

 to the very general use of water as a solvent, and its 

 presence in most natural bodies c . It was, in fact, upon 

 purely negative (vol. ii. p. 16) and weak evidence that the 

 opinion had been founded. 



Many experimenters attributed peculiar and even myste- 

 rious powers to the poles of a battery, likening them to 

 magnets, which, by their attractive powers, tear apart the 

 elements of a substance. By a most beautiful series of 

 experiments d , Faraday proved conclusively that, on the 

 contrary, the substance of the poles is of no importance, 

 being merely the path through which the electric force 

 reaches the liquid acted upon. Poles of water, charcoal, 

 and many diverse substances, even air itself, produced simi- 

 lar results, or if the chemical nature of the pole entered 

 at all into the question, it was as a disturbing agent. 



It is a most essential part of the theory of gravitation 

 that the proximity of other attracting particles is wholly 

 without effect upon the attraction existing between any 

 two molecules. Two pound weights weigh as much to- 

 gether as they do separately. Every pair of molecules in 

 the world have, as it were, a private communication, apart 

 from their relations to all other molecules. Another un- 

 doubted result of experience pointed out by Newton 6 is 

 that the weight of a body does not in the least depend 



c 'Experimental Researches in Electricity/ vol. i. pp. 133, 134. 



d Ibid. vol. i. pp. 127, 162, &c. 



e ' Principia,' bk. iii. Prop. vi. Corollary i. 



