[ 3 26 ] 
before in the preceding experiments ; and, inftead of 
being minus , they were now plus $ for the amber 
caufed them to accede . 
By the balls receding to a greater diftance in this 
la ft cafe than in any other experiment I have yet pro- 
duced, and the flow of the fluid, during the natural 
Jiate of the ftone, being from the minus to the plus 
fide, we have produced another proofs that the refin- 
ance is leaf at the minus fide of the fone : and from 
this caufe, the tendency of the fluid from the balls 
towards the fione muft be greater, than when the fluid 
tended from the ftone towards the balls. But there is 
a reflftance appertaining to the wood, that was ob- 
ferved before, and which muft be taken into the ac- 
count, though it is the fame in each experiment. 
Neverthelefs, fince the tendency of the fluid is differ- 
ent when different fldes of the fone are expofed, dif- 
ferent degrees of the eledtric fluid will be accumu- 
lated. Hence we fee the reafon why, upon removing 
the fone from off the wood, as in this lad experi- 
ment, more of the accumulated fluid muft have 
flowed in, than flowed out , becaufe the balls were elec- 
trified plus. 
HAVING endeavoured to explain thele three dif- 
ferent fates of the Tourmalin , caufed by different ap- 
plications of heat , I fhall now offer fome farther ex- 
periments in which fridlion is concerned, and com- 
pare them with other experiments of the vitreous and 
refinous kind, in order to obferve how far they agree 
with one another, and whether the principles here 
advanced are conftant and uniform. 
Exp . 20. The Tourmalin being again fixed to the 
wax, I gave the convex fide one flight rub with my 
finger , 
