CHAP. II. TOLTAIO OIBCLE. 13 



I shall confine my remarks to the former, and state 

 what the chemical theory is *, 



' The chemical theory,' says Faraday, ' assumes, 

 that at the place of action the particles which are in 

 contact act chemically upon each other, and are ahle 

 under the circumstances to throw more or less of 

 the acting force into dynamic force ; that in the 

 most favourable circumstances the whole is con- 

 verted into dynamic force ; that then the amount of 

 current force produced is an exact equivalent of the 

 original chemical force employed ; and that in no 

 case (in the voltaic pile) can any electric current be 

 produced, without the active exertion and con- 

 sumption of an equal amount of chemical force 

 ending in a given amount of chemical change.' 



Let us now take a simple voltaic circle, and study 

 the changes that occur in it. I shall assume my 

 readers to be acquainted with the origin of the 

 terms, ' electrode,' ' anode,' and ' cathode^.' If we take 

 a vessel containing dilute sulphuric acid, and dip 

 two rods, one of zinc and the other of platinum, 

 into it, so long as they remain separate no action 

 occurs on the platinum, but gas is evolved on the 

 zinc, where chemical action is taking place. Let the 

 two rods be brought into communication by means 

 of a conducting substance, such as a metallic wire, 



« I cannot do better than refer my readers to Faraday's 

 Paper, On the source of the power in the Voltaic pile. Expe- 

 rimental Researches, vol. ii. p. 18. 



i- Ibid. vol. i. p. 195. 



