320 Mr. Srnee on the Galvanic Properties of Metals, 



ment of the metals, and the diminution attending its opera- 

 tion appeared to arise from deficiency of acid, for it was in- 

 stantly restored by a Httle strong sulphuric acid in each cell. 

 Where the battery is required to possess the same power for 

 a long period, it might be advisable to separate the metals by 

 a porous earthenware vessel, or what answers the purpose 

 equally well, b}' a thick paper bag, the joinings of which must 

 be effected by shell-lac dissolved in alcohol. By these means, 

 the sulphate of zinc is retained on the zinc side of the battery. 

 The use of porous tubes, however, appears from observation, 

 as far as my battery is concerned, to be nearly superfluous, at 

 any rate in most cases ; for I find, that after a battery arranged 

 as WoUaston's had been at work in the same fluid for forty- 

 eight hours, it had no zinc deposited on the silver. It is worth 

 remarking, that during the last 24 hours contact had not been 

 broken for a single instant. Notwithstanding these experi- 

 ments, however, it may be as well in an extensive battery to 

 use porous plates. 



The battery may be arranged like the pot batteries, but 

 I should greatly prefer the troughs, such as used for WoUas- 

 ton's batteries, from the convenience of packing, and from a 

 battery of the same surface requiring so small a space. A 

 battery may be constructed to form a most powerful calori- 

 motor. It may also be arranged as a circular disc batteiy. 

 Or it may be made as a Cruickshanks, each cell being di- 

 vided or not by a flat porous diaphragm. Whatever ar- 

 rangement is adopted, the closer the zinc is brought to the 

 platinized metal, the gi'eater will be the power. 



The generating fluid which is to be employed is water, with 

 one-eighth of sulphuric acid by measure ; and the zinc ought 

 always to be amalgamated in the first instance, as that pro- 

 cess will be found very ceconomical from its stopping all local 

 action, and the amalgamation will be found not to require 

 repeating, because there is no fear of copper being thrown 

 down on the zinc, which occasionally happens in the sulphate 

 of copper batteries. 



The battery thus constructed is the cheapest and least 

 troublesome in action that has ever been proposed, and from 

 the smallness of its bulk will be found very valuable to electro- 

 magneticians. It is second in power only to the nitric acid 

 batteries, the objections to which have been already noticed. 

 For medical purposes, with a Bachoffner's apparatus, a bat- 

 tery composed of platinized silver two inches each way will 

 be found sufticient. 



To recapitulate the processes of the formation of a battery: 

 first the platina, silver, or plated copper must be roughened, 

 the two latter with nitric acid, and afterwards washed, The 



