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but the principal {hock is felt in the bread, as if a 
blow from each fide met there. This plain and 
fimple experiment feems obvioufly to fugged to ob- 
fervation, the exidence of two didind powers, adding 
in contrary directions : And I believe it would be held 
as a fufficient proof by any who diould try the expe- 
riment, with a view to determine the quedion limply 
from their own perceptions. 
But as I am fenfible, that the proof of any import- 
ant point in philol'ophy, ought not to depend upon 
the perceptions of this or that particular perfon, I 
judged it neceffary to have recourfe to experiments, 
the refult of which might admit of no ambiguity. 
The fortunate difcovery of M. Mufchenbroek and 
M. Allamand, with the improvements that have fince 
been made upon it, puts it in our power to increafe 
eledricity to what degree we pleafe. I did not there- 
fore defpair of the means of bringing this matter to a 
fair decifion. I exported, that if an eledrical droke 
fhould be made to pals through a folid body, with fo 
much force as to pierce and tear the fubdance of it, 
fuch marks would be left, as might enable us, with 
certainty, to trace the courfe of the eledrical power 
in its pafiage through the body. 
Having no apparatus of my own capable of pro- 
ducing fuch effeds, I had recourfe to a worthy mem- 
ber of this Society, dodor Franklin, who was pof* 
felled of a very good one. I had communicated all 
my obfervations to this gentleman as they occurred, 
and, in return, met with an ingenuity and can- 
dour, that render him as edimable in private life, as 
the improvements he has introduced into eledricity, 
and particularly his difcovery in relation to thunder 
