EPOCH OF DAVY AND FARADAY. 295 



instant, "a capital experiment." This discovery was soon followed by 

 that of the decomposition of soda ; and shortly after, of other bodies of 

 ihe same kind ; and the interest and activity of the whole chemical 

 world were turned to the sxibject in an intense degree. 



At this period, there might be noticed three great branches of specu- 

 lation on this subject ; the theory of the pile, the theory of electricai 

 decomposition, and the theory of the identity of chemical and electrical 

 forces ; which last doctrine, however, was found to include the other 

 two, as might have been anticipated from the time of its first 

 suggestion. 



It will not be necessary to say much on the theories of the voltaic 

 pile, as separate from other parts of the subject. The contact-theory, 

 which ascribed the action to the contact of different metals, was main- 

 tained by Volta himself; but gradually disappeared, as it was proved 

 (by Wollaston 6 especially,) that the effect of the pile was inseparably 

 connected with oxidation or other chemical changes. The theories 

 of electro-chemical decomposition were numerous, and especially 

 after the promulgation of Davy's Memoir in 1806 ; and, whatever 

 might be the defects under which these speculations for a long time 

 labored, the subject was powerfully urged on in the direction in which 

 truth lay, by Davy's discoveries and views. That there remained 

 something still to be done, in order to give full evidence and consistency 

 to the theory, appears from this ; that some of the most important 

 parts of Davy's results struck his followers as extraordinary paradoxes ; 

 for instance, the fact that the decomposed elements are transferred 

 from one part of the circuit to another, in a form which escapes the 

 cognizance of our senses, through intervening substances for which they 

 have a strong affinity. It was found afterwards that the circumstance 

 which appeared to make the process so wonderful, was, in fact, the 

 condition of its going on at all. Davy's expressions often seem to indi- 

 cate the most exact notions : for instance, he says, " It is very natural 

 to suppose that the repellent and attractive energies are communicated 

 from one particle to another of the same kind, so as to establish a con- 

 ducting chain in the fluid ; and that the locomotion takes place in 

 consequence ;" 7 and yet at other times he speaks of the element as 

 attracted and repelled by the metallic surfaces which form the poles ; 

 a different, and, as it appeared afterwards, an untenable view. Mr. 

 Faraday, who supplied what was wanting, justly notices this vagueness. 



Phil. Trans. 1801, p. 427. Paris, i. 154. 



