Royal Society. 329 



of accessible discoveries, which the law of substitutions re- 

 veals to the eyes of the chemist, justifies a remai'k of my dear 

 friend M. Ampere, having so warm a heart and a mind so 

 rich in delicate perceptions. When I was speaking to him 

 of the law of substitutions, he also, at first, confounded it 

 with the ordinary equivalent actions; but when I had de- 

 veloped the views, still very incomplete, which I was already 

 endeavouring to attach to them, " Ah ! my friend," said he, 

 " how I pity you ! you have found work for your whole life." 

 A prediction which would have been realised, if so many 

 minds of a higher order, taking up the law of substitutions, 

 had not given it a flight which makes my part of the work 

 much less necessary. 



[To be continued.] 



LV. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



Feb. 13, T^HE reading of a paper, entitled " Experimental Re- 

 1840. -*- searches in Electricity, Sixteenth Series." On the 

 source of power in the Voltaic pile. By Michael Faraday, Esq., 

 D.C.L., F.R.S., &c., was resumed and concluded. 



The determination of the real source of electrical power in gal- 

 vanic combinations has become, in the present state of our know- 

 ledge of electricity, a question of considerable importance, and one 

 which must have great influence on the future progress of that 

 science. The various opinions which have been entertained by phi- 

 losophers on this subject may be classed generally under two heads ; 

 namely, those which assign as the origin of voltaic power the simple 

 contact of dissimilar substances, and more especially of diff'erent 

 metals ; and secondly, those which ascribe this force to the exertion 

 of chemical affinities. The first, or the theory of contact, was devised 

 by Volta, the great discoverer of the Voltaic pile ; and adopted, 

 since it was promulgated by him, by a host of subsequent philoso- 

 phers, among the most celebrated of whom may be ranked Pfatf, 

 Marianini, Fechner, Zamboni, Matteucci, Karsten, Bruchardat, and 

 also Davy ; all of them bright stars in the exalted galaxy of science. 

 The theory of chemical action was first advanced by Fabroni, Wol- 

 laston, and Parret ; and has been since further developed by Oersted, 

 Becquerel, De la Rive, Ritchie, Pouillet, Schoenbein, and others. 

 The author of the present paper, having examined this question by 

 the evidence afforded by the results of definite electro-chemical 

 action, soon acquired the conviction of the truth of the latter of 

 these theories, and has expressed this opinion in his paper, pub- 

 lished in the Philosophical Transactions for 1834. 



The author, after stating the fundamental doctrine laid down by 



