* G. W. Hough on the Galvanic Battery. 185 
end of three days and at the end of five days there will be 
scarcely any action. On the contrary with Hill’s element, of 
the size before described, g. will continue uniform for more than 
thirty days, and will be but little less at the end of fifty days. 
Most of the writers on galvanism seem to imagine that 
sulphuric acid is essential for exciting the battery, but our ex- 
periments show that this is not the case; in fact we consider 
it a detriment ; for if too great a quantity is used, crystals of 
sulphate of zine are deposited on the zinc, thereby greatly les- 
sening g. It seems to me that the only office of the sulphuric 
.acid, is to make the water a better conductor ; since nitric acid, 
muriatic acid, salt, sulphate of copper, or sulphate of zinc, will 
answer equally well, By using a solution of s.z, of a certain 
specific gravity, the same quantity and electro-motive force is 
obtained, as with sulphuric acid. This is also true for Grove’s 
and the bi-chromate of potash battery. 
The use of a number of porous cells in the same jar.—Since 
the decrease of g. is due to the formation of s.z., the question 
naturally arises, how can a battery be constructed that will 
give a uniform current for a long period of time? The an- 
swer is plain, we must increase the capacity of the cell in which 
the zine is placed. 
In a two-gallon stone jar, three porous cells were placed with 
a sheet of copper surrounding them. The current was then 
passed through the galvanometer and rheostat, and sufficient 
resistance inserted to make gq. equal to that due to a single cell, 
when used alone. The amount of s.z. formed in a given time 
was then measured, when it was found each cell made as muc 
8.2. as if only a single one had been employed. This combina- 
tion showed very great local action. Nothing, therefore, would 
be gained by such an arrangement, but on the contrary a much 
greater amount of zine would be consumed without advantage. 
We next had constructed large porous cells 6 inches in dia- 
meter and 7 inches high having a capacity of 180 cubic inches. 
Our previous experiments enable us to calculate with consider- 
able precision the length of time one of these elements will 
maintain a maximum current of electricity. Allowing 5:7 
cubic inches for the amount of liquid saturated daily between 
the limits 12° to 40°, it is apparent that a battery of this size 
Should remain constant for more than 30 days, without any 
external resistance being introduced in the circuit. 
electro-magnets are operated, as the external resistance should 
at least be equal to that of the battery, the current would re- 
main constant for more than two months ona continually 
closed circuit. 
Am. Jour. Sc1.—SEconp.Series, Vou. XLVIII, No. 143,—Sepr., 1869. 
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