aes 
Self-sustaining Voltaic Battery. 57 
The quantity near the battery is very great compared with the 
quantity on the part remote from the battery, for the insulation is 
always imperfect; and of the whole quantity that leaves the bat- 
tery, only a small proportion reaches the remoter part. But to 
get all the waste included in my measurement, I measured near 
the battery, and found when the line was in good working order, 
the quantity of the electricity was that represented by the solu- 
tion of one grain of zinc per hour. Sometimes the line would 
work well with much less than a grain; and often after the bat- 
teries had been recently charged, the quantity was ten grains; 
but mostly, when the line was in fine order, the quantity was 
about the grain. 
the mercury ) say fifty pounds, which is a cube of less than six 
luches square. 
Thave lately had a fair opportunity of knowing the value of 
this battery. In May last, I charged six cells, which were put 
ina box in the upper laboratory, to be -used in the experiments 
on photographic engraving, The battery has since been a 
Most daily use for gilding deep-sea thermometers, or other in- 
Struments, or else in the experiments. During the six months 
Which have elapsed, it has been used probably 2000 times, in 
Which there was nothing more required to get the current than 
_ 0 complete the circuit. During the intensely hot spell of the 
past summer, L three times added a little water to supply the loss 
from Evaporation, aud these were the only times the box was 
Opened, 
Stcoxp Sates, Vol. XXI, No. 61.—Jan. 1856. 8 
