184 G. W. Hough on the Galvanic Battery. 
the zinc, and metallic copper is deposited on the copper plate. 
A long series of experiments were instituted to determine the 
rate of — of the s.z., during the various conditions of 
the batt A Hill’s element was put on a closed circuit 
through the galvanometer, without any external resistance, and 
the specific gravity of the s.z. was measured daily, by means 
of a Baumé hydrometer, The indications of the galvanometer 
needle and the temperature, was also ascertained at the same 
time. The jar containing the liquid was 7 inches high and 6 
inches in diameter. The zinc and copper plates each presented 
a surface of 28 co tg inches. The distance between — i 
was 52 inches. The battery was started wit Se. 
lt isa feadumanadl principle that the formation of s.2%. is 
directly proportional to the quantity of electricity oe in 
the circuit. This would be strictly true, provided there was 
no local action ; but actual experience demonstrates that this 
condition is never fulfilled. On laying down the daily results 
in the form of a curve, having the specific gravity of the s.2 
for one ordinate, and the time for the other, it was found that 
the observations could be well represented by an equation of the 
second degree in which 4,=+1:66° and 4,=—0:08°. 
this element, the amount of liquid intabbind with s.z. between 
the limits 12° to 40° B. ., was 3°6 cubic inches daily, A second 
element of the same size in which the distance between the 
plates was reduced to 4 inches, gave similar results. But the 
amount of liquid saturated daily was nearly twice as great, 
with but a small increase in the quantity of electricity gene- 
rated ; showing a much greater local action. 
The experiments with a Daniell’s element of the usual size, 
using a porous cell 24 inches in diameter and 7 inches high, 
e 5: : — a for the amount of liquid —— daily, 
al condition of the element. As q. wa nearly 
double cuts oie Hill’s element, and the amount of liquid satu- 
rated, less in proportion, it shows less local action. From 
these experiments it follows that once ha aving determined 4. 
the length of time the battery will maintain the currents at its 
normal force can readily be computed ; since it depends eD- 
tirely on the capacity of the cell holding the sulphate of zinc. 
With a porous cell of the usual size, when no external resist- 
ance is introduced, the battery will begin to decrease at the 
