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 little 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 earthenw'are 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 Wollaston’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, how’ever, 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 Wollas- 
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 battery. 
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 greater w ill 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 oeconomical from its stopping all local 
action, and the amalgamation will be found not to require 
repeating, because there is no fear of copper being throwm 
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^mallness 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 Bachoffher’s apparatus, a bat- 
tery composed of platinized silver tw'o inches each way will 
be found sufficient. 
To recapitulate the processes of the formation of a battery: 
first the plabina, silver, or plated copper must be roughened, 
the two latter with nitric acid, and afterwards washed. The 
