[ 3*9 ] 
the balls receded from them, but rather with a greater 
force from the convex fide, than from the plain fide. 
This appearance proves an increafe of the power in 
the flone ; becaufe it continued to aCt for a time like 
other bodies electrified plus . And in regard to the 
different forces of the two fides, that will be particu- 
larly confidered hereafter. 
Exp. 4. After a fhort time, the 'Tourmalin being 
colder, and the remaining heat more equally diffufed, 
it changed its laft ftate to a plus and minus one j for 
the plain fide made the balls accede , and the convex 
fide made them recede. 
This change feemed to arife from fome alteration, 
on or near its furfaces, by having the heat equally dif- 
fufed throughout the ftone: if it was not fo, I fee 
no reafon but that the Tourmalin fiiould continue to 
be eledtrified plus on both fides, whiifl any eleCtrical 
figns remained. 
Exp. y. I now held the plain fide as near the flame 
as I had done the convex one; and inftead of both 
fides being electrified plus, they were electrified mi- 
nus, for each fide caufed the balls to accede. 
From this experiment, I had reafon to believe that 
the flone was emptied (if I may fo fay) of its electri- 
city; becaufe it continued to aCt for a time like other 
bodies electrified mmus. 
Exp. 6. After the fame length of time as in the 
fourth experiment, the Tourmalin being colder, it 
changed its ftate alfo ; for the convex fide made the 
O t 
balls recede , and the plain fide continued to make 
them accede , as they had done before, 
This 
