G. W. Hough on the Galvanic Battery. 189 
which the zine is placed should have a capacity of at least 150 
cubic inches. As the resistance of large clay cells is more than 
three times as great as for those made of leather, the latter 
are preferred ; since with the same surface of zinc, g. is nearly 
doubled. The constant use of leather cells during the past 
year tully demonstrates their superiority over those made of 
white clay. For it is found in practice that for working mag- 
nets such as are used in telegraph offices for local sounders, one 
element as described above gives more effective working force 
than two of those in ordinary use. .The zine casting may be 
of any form ; for cells of this size, it should have an external 
surface of 50 square inches. 
The battery should be started with s.z. at 15°° B. specific 
gravity. Sulphuric acid should never be used in the cell con- 
taining the zinc. Crystals of s.c. are suspended in a bag or 
perforated cup near the top of the liquid surrounding the nega- 
tive plate, in order to keep the solution at saturation. After 
a battery has been in constant use for a number of months, 
crystals of s.c. will be found precipitated on the bottom of the 
Jar. When this is the case, the liquid must be poured in 
another vessel, and all the s.c. removed, as it seems to lessen 
g- During cold weather the battery may be improved by add- 
ing occasionally a little sulphuric acid to the s.c, solution. 
Between 40° and 100° Fahr., the specific resistance of the li- 
quids is increased about one sixth for every 10° decrease of 
temperature. ‘It is not desirable therefore, to work the battery 
at a temperature below 50° Fahr. 
The zinc need not be amalgamated, but it should be cleaned 
Once in two or three months, and all the sediment removed from 
the porous cell. 
When the specific gravity of the s.z. approaches 40° B. one 
half of the liquid should be removed, and fresh water added. 
It is always best, however, to keep the specific gravity of the 
8.% between the limits 15° to 38° B. 
ug; 
the orifice in the vnins plate. The battery should be examined 
9ccasionally with the hydrometer, and the specific gravity oi 
the liquid never allowed to become greater than 36°° B. 
