on the EleStrophorus. 1037 
obftru&ion in its free paflage to another neighbouring 
body by the interpolation of a. non-conduCting body (fuch 
as dry air, glafs,. 8tc.) forces by its repulfive power the elec- 
tric fluid naturally contained in all bodies to the further- 
moft extremity of the neighbouring body,., fo as to excite 
in its neareft extremity a kind of defeCt of the eleCtrie 
fluid, or a kind of vacuum,, till at laft the accumulation 
of the eleCtrie fluid becomes fo great upon the electrified 
body, that it overpowers the reflftance of the interme- 
diate non-conduCting fubftance, forces its way through it, 
and' rullies in the form, of a fpark upon the neighbour- 
ing body.. 
If the eleCtric fluid be thrown upon the furface of a 
pane of glafs, coated on both fides with a metallic fub- 
ftance, fuch as tin- foil ; the fluid, finding an obftruCtion 
to its paflage through the body, is croudedupon that fur- 
face of the glafs which has received it; forces the eleCtrie 
fluid out of the other furface, if fome conducting body 
is near it, or in contaCt with it, and can convey it away ;, till 
this fluid becomes fo much crouded upon that furface as 
to overpower the refiftance of the glafs, .and to force its way 
through the fubftance of the glafs,, in order to diffufe it- 
felf upon the other furface, upon which was produced a 
kind of vacuum. The glafs being thus rent is no longer 
able to be what is called charged; but after the crouded 
elec- 
