[ 47 ] 
which arc placed Books, and feveral other Non- 
eledrics 5 and that the Motions of the light Bodies 
underneath correfpond with the Motions of the glafs 
Tube held over them, the Elcdricity feeming inftan- 
taneoufly to pafs through the Books and the Glafs. 
But this does not happen, till the Eledricity has fully 
impregnated the Non-eledrics, which lie upon the 
Glafs 5 which received Eledricity 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-dedrics. But if the thinneft 
Non-eledric, even the fineft Paper, as I before men- 
tioned, is held in the Hand of a Man at the fmalleft 
Diftance over the Leaf- Gold, and the Eledricity is 
not flopped, not the leaft Power will be exerted, 
and the Gold will lie ftill. I mu ft here remark like- 
wife, that this Law of Eledricity is fo conftant and 
regular, that I have not found one Deviation from 
it y fo that even the Quicklilver, fpread thin, as it 
ufually is at the Back of a Plate of a Looking-glafs, will 
prevent the Pafllng thro* of the eledrical Attraction, 
unlefs flopped by an Originally-electric. This Pene- 
tration of the electrical Power through Originally- 
electrics is much greater than has hitherto been 
imagined, and has caufed the Want of Succefs to 
great Numbers of Experiments. I have; been at no 
fmali 
makes the Glafs, as has been before ^ demonftrated, a Conductor 
of Electricity : Secondly, As Heat enlarges the Dimenfions of ail 
known Bodies, and, confequently caufes their conftituent Parts to 
recede from each other, the eledrical Effluvia^ palling in (trait 
Lines, find, probably, a more ready Paftage through their Pores. 
^ See Numb. 477, of thefe Tranfaffions , p, 486.. 
