2 02 Mr. cavendish on the Torpedo. 
end on fteel pins as centers, with cork balls about ~ of an 
inch in diameter fixed on the other end. The way by 
which I eft i mated the divergence of tliefe balls, was by 
feeing whether they appeared to coincide with parallel 
lines placed behind them at about ten inches diftance ; 
taking care to hold my eye always at the fame diftance 
from the balls, and not lefs than thirty inches off. To 
make the ftraws conduit the better, they were gilded, 
which caufes them to be much more regular in their 
effeCt. This electrometer is very accurate; but can be 
ufed only when the electricity is very weak. It would be 
eafy, however, to make one on the fame principle, which 
fhould be fit for meafuring pretty ltrong electricity. 
The inftrument by which I found to what diftance 
the fpark would fly is reprefented in fig. 2.; it differs 
from Mr. lane’s electrometer no otherwife than in not 
being fixed to a jar, but made fo as to be held in the 
hand. The part abcdefgklm is of baked wood, the 
reft of brafs; the part gkl being covered with tinfoil 
communicating with the brafs work at fg; and the part 
abm being alfo covered with a piece of tinfoil, com- 
municating with the brafs work at cd. 
I next took four jars, all of the fame fize; electrified 
one of them to a given degree, as fhewn by the electro- 
meter ; and tried the ftrength of the fhock which it gave ; 
and found alfo to what diftance the fpark would fly. I 
then took two of the jars, electrified them in the fame 
degree as before, and communicated their electricity to 
the two remaining. The fhock of thcfe four jars united, 
was 
