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conducted on a larger scale than those of M. Becquerel, endeavoured 

 more closely to imitate the arrangements of nature, by introducing, 

 bet^yeen the substances acted on, walls of clay, in imitation of the 

 " flucan courses" in the Cornish mines ; these walls performing the 

 same functions as the moistened clay in M. Becquerel's experiments ; 

 and he infers from his results, that the phaenomena presented by the 

 mineral veins of Cornwall are explicable on principles which are 

 similar to those pointed out by M. Becquerel. It is thus rendered 

 highly probable that the long-continued action of electricity of low 

 tension has been at least one of the means by which crystallized 

 bodies now existing in mineral veins have been produced. 



But quite independently of the bearing of M. Becquerel's results 

 on a question of great geological interest, the formation of crystals 

 of metallic sulphurets and other substances by the agency of elec- 

 tricity was a great step in chemical science. As M. Becquerel very 

 justly observes, the two branches of chemistry, analysis and syn- 

 thesis, are at present in very different states. With the exception 

 of crystals derived from aqueous solution, — which are by far the 

 least abundant of natural crystals, — and a few from fusion, the 

 great mass of crj^stallized bodies existing in nature had as yet re- 

 mained inimitable by chemical processes. In the Memoirs re- 

 ferred to, not only are experiments described by which crystals 

 of several of these substances have been obtained, but the principles 

 are pointed out, by the application of which we may anticipate that 

 large classes of others will be produced. M. Becquerel has thus 

 opened a new field for inquiry and discovery, in which he has him- 

 self gathered the first fruits, but which still offers to future labourers 

 the prospect of an abundant harvest of knowledge as regards both 

 the recomposition of crystallized bodies, and also the processes 

 which may have been employed by nature in the production of 

 such bodies in the mineral kingdom. 



A Copley Medal has been awarded to John Frederick Danieil, 

 Esq., for his two papers on Voltaic Combinations, published in the 

 Philosophical Transactions for 1836. 



The Council are desirous of testifying, by this award, their sense 

 of the great value of Mr. Daniell's invention of a new form of the 

 voltaic battery, capable of producing, for a considerable length of 

 time, a perfectly equal and steady current of electricity. The prin- 

 ciples on which his apparatus, which he terms the constant battery^ 

 is constructed, were the results of a series of well-devised experi- 

 ments, directed to the discovery of the cause of those great and 

 often rapid variations in the power of the ordinary battery, which 

 have hitherto limited its utility when employed for purposes of 

 philosophical research, and the removal of which has greatly ex- 

 tended the range and multiplied the applications of this powerful 

 instrument of chemical analysis. 



The train of reasoning that led Mr. Danieil to this discovery, 

 originated in an inquiry which he undertook with the view of de- 

 termining with precision the influence exerted by the different parts 

 of the voltaic battery in their various forms of combination. For 



