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This change Teemed likewife to arifi* from Tome 
alteration on the furfaces of the tourmalin , by haying 
the heat equally diffufed throughout the ftone : if it 
was not fo, I (ee no reafon but that the tourmalin 
fhould continue to be electrified minus on both fides, 
whilft any eletfxical figns remained. 
I was naturally led next to examine at which fur- 
face of the tourmalin the fluid entered (if any did), 
whilft it continued heating. 
Exp . 7. Flame being improper for my purpofe, 
becaufe the eleCtric fluid is readily difiipated by its 
prefence, I made choice of an iron rod, at the end of 
which was a round knob. This was heated, and af- 
terwards brought to a certain diftance from the balls, 
in order to fee if they were moved by it: but not per- 
ceiving tire leaft motion, I interpofed the tourmalin , 
with the convex fide next the balls. They acceded 
a little, and when I removed the heated iron, they 
returned to their place again. I then brought the 
iron nearer to the tourmalin than before: the balls 
in this cafe moved with vigour towards the ftone, and 
continued in contatt with it for a confiderable time ; 
and, after that, they receded from it. 
On examining the balls, I found they had loft all 
their plus ele&ricity, and were ele&rified minus. I 
alfo obferved that the ftone itfelf was minus on both 
ftdes. 
I gathered from this experiment, that the elcttric 
fluid flowed from the balls towards the ftone ; becaufe 
they not only loft their own plus electricity, but were 
electrified minus : and, as the tourmalin was minus 
alfo on both fides, a quantity of clettric fluid mufl 
have 
