350 Boy al Society : Report of the Council : 



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 Daniell, 

 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. Daniell 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 

 this purpose he contrived an apparatus which he designates by the 

 name of the dissected battery, and which consists of a series of cylin- 

 drical glass vessels capable of holding the fluid electrolyte, with a 

 pair of metallic plates immersed in it, each plate communicating 

 below by means of a separate wire, with a small quantity of mercury, 

 as the medium of the various communications which may at pleasure 

 be made with other metallic parts of the apparatus. This arrange- 

 ment affords peculiar advantages for studying the difference of effect 

 in reference to the quantity and the intensity of the electric current, 

 consequent on the different modes of connecting the elements of the 

 battery, and also the influence of retarding forces resulting from 

 other modes of connexion. In the course of these researches, 

 Mr. Daniell, observing the great extent of negative metallic surface 

 over which the deoxidating influence of the positive metal appeared 

 to manifest itself, was induced to institute a more careful examina- 

 tion of the circumstances attending this class of phsenomena, and was 

 led to the discovery of the gradual deposition of zinc on the platina 

 plates being the principal cause of the progressive decline of the 

 power of the battery. It was then that the means of counteracting 

 this tendency presented itself to his mind. His plan consists in the 

 constant application of a solution of sulphate of copper to the copper 

 surface, while, at the same time, diluted sulphuric acid is constantly 

 applied to the zinc surface, on which it exerts an oxidating and a 

 solvent power, and is constantly renovated as it becomes charged 

 with zinc. The two fluids are separated from one another by a par- 

 tition formed of membrane, or other porous substance, which pre- 

 vents intermixture, but offers no obstacle to the transmission of 



* Abstracts of Mr. Daniell's papers were given in Lond. & Edinb. Phil 

 Mag., vol. viii. p. 421, and vol. ix. p. 376. 



