C 7° r 1 
other Non-Elecirics j and that the Motions of the 
light Bodies underneath correfpond with the Motions 
of the glafs Tube held over them, the Eledricity 
feeming inftantaneoufly to pafs thro" the Books and 
the Glafs. But this does not happen, till the Elec- 
tricity has fully impregnated the Non-eledric$> 
which lie upon the Glafs j which received Elec- 
tricity is flopped by the Glafs $ and then thefe Non- 
Eledrics dart their Power diredly through the upper 
Part of the Glafs, after the Manner of Originally- 
Eledrics. But if the thinnefl Non-Eledric, even 
the fineft Paper, as I before mentioned, is held in 
the Hand of a Man at the fm ailed: Diftance over the 
the Leaf-Gold, and the Electricity is not flopped* 
not the leaft Power will be exerted, and the Gold 
will lie ftiil. I muft here remark likewife, that this 
Law of Electricity is fo conftant and regular, that I 
have not found one Deviation from it ; fo that even 
the Quickfilver, fpread thin, as it ufually is at the 
Back of a Plate of a Looking-Glafs, will prevent 
the parting through of the eledrical Attraction, unlefs 
flopped by an Originally -Eledric. This Penetration 
of the eledrical Power through Originally-Eledrics 
is much greater than has hitherto been imagined, 
and has caufed the Want of Succefs to great Num- 
bers of Experiments. I have been at no fmall Pains 
to determine, how far this Power can penetrate 
through a dry Originally-Eledric, and have found, 
by repeated Trials, that either in a Cake of Wax 
alone, or of Wax and Refin mixed, when the Elec- 
tricity is very powerful, it has parted, I fay, in ftrait 
Lines through thefe Cakes of the Thicknefs of two 
Inches and -A $ but I never could make it a ft through 
one of two inches -^5 for in this it was perfedly 
flopped 
