Page:Proceedings of the Royal Society of London Vol 4.djvu/46

Rh 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 phenomena, and was led to the discovery of the gradual deposition of zine 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 galvanic action. Two principal objects are accomplished by this arrangement of the constituent parts of the battery; first, the re- moval out of the circuit of the oxide of zinc, the deposit of which gradually reduces, and at length suspends, the action of the ordinary battery; and secondly, the absorption of the hydrogen evolved upon the surface of the copper, without the precipitation of any substance tending to counteract the voltaic action of that surface

The advantages likely to arise to science from the invention of the constant voltaic battery are numerous and important. Mr. Da- niell has shown how it may be made to supply a measure of chemical affinity, and has applied it with effect in the investigation of the in- fluence of changes of temperature on voltaic action. The construc tion of a constant battery of large dimensions, which he has recently completed, has already opened new views of the possible application to economical purposes of the powers of voltaic electricity, an agent of which the influence appears to be so energetic and so widely dif- fused throughout nature.

The Council have adjudged one of the Royal Medals, in con- formity with the announeement made in 1834, to Mr. Whewell, for his series of Researches on the subject of the Tides, which have been published in our Transactions during the last three years. Mr. Whewell's researches have been chiefly directed to the three following points: first, the motion of the tide-wave at different points