F 361 ] 
exactnefs, to the degree in which the body to which 
it is connected is electrified ; but this inconvenience 
is eafily remedied, by moiftening the Item and the 
index, for the femicircle cannot be too dry. 
I find by experience, that this electrometer 2n- 
fwers all the purpofes I have mentioned, with the 
greateft eafe and exact nefs. I am now fure of the 
force of any explofion before a difcharge of a jar or 
battery, which I had no better method of gueffing 
at before, than by prefenting to them a pair of Mr. 
Canton’s balls, and obferving their divergency at a 
given difiance ; but the degree of divergency was 
iiill to be guefied at by the eye, and the balls can 
only be applied occafionally ; whereas this infirument, 
being conftantly fixed to the prime conductor or the 
battery, fhews, without any trouble, the whole pro- 
grefs of the charge ; and, remaining in the fame fi- 
tuation, the force of different explofions may be as- 
certained with the utmofl exactnefs before the dif- 
charge. 
If a jar be loaded with pofitive electricity, and I 
want to know the exact time when, by attempting to 
charge it negatively, it firfi becomes difcharged, I fee 
every ftep of its approach to this ftate by the falling 
of the index j and the moment I want to feize, is 
the time when it has got into a perpendicular fixa- 
tion, which may be obferved, without the leaf!; dan- 
ger of a miftake. Accordingly I find that, in this 
.cafe, not the leaft fpark is left in the jar. If I con- 
tinue the operation, the index, after having gained 
its perpendicular pofition, begins to advance again, 
and thereby fhews me the exact quantity of the op- 
pofite electricity that it has acquired. 
Vol. LXII. A a a 
Confi- 
