C 394 ] 
EXPERIMENT V. 
I infulated the rubber of my machine, and hung 
a pair of Mr. canton’s balls upon the prirrie-con- 
dudlor. I then worked the machine, and having 
taken off a fpark, or two, to draw off the electri- 
city naturally inherent in the rubber, &c. I ob- 
ferved the divergence of the balls; which was very 
great ; in fo much that the firings were bent : and 
on approaching the back of the rubber with a 
fmoking green wax taper , juft blown out, (the 
fmoak of which was inftantly attracted to it,) they 
diverged no wider (a K I then took off the balls, and 
placed my own electrometer in its ftand, upon the 
prime-condu6tor [tab. xnr. fig. 4] ; and having 
taken off a fpark, or two, as before; I again worked 
the machine, to obferve the repellency of the in- 
dex from the ftem ; and found it constantly to vi- 
brate between five, and ten degrees, of the quadrant, 
which was divided into fifteen. I then brought 
the fmoking taper, within four, or five inches, of 
the back of the rubber, as before; and obferved, 
that on the attraction of the fmoak to it, the index 
prefently began to rife; and in a very fhort time, 
got up to right angles. I repeated the experiment, 
feveral times, with the fame fuccefs. I then tried 
the experiment by bringing my finger to the fame 
diftance from the rubber, and pointing towards it; 
but this, in many trials, had not the leaft effeCt. 
The taper likewrfe, when held at the fame dif- 
tance, and not fmokingy had no effeCt at all. .1 am 
(a) For this experiment, the back of the infulated rubber 
fliould be perfectly fmooth : mine, is of wood ; with the leather 
pafted down clofely to it; foas to leave no points. 
convinced 
