[ 44 ° ] 
can fed by glafs, is once traced, that which is cauled 
by wax, amber, or refin, follows of courfe. The 
eieCtric fluid, when it is emitted from any fmooth 
lurfaceof metal without edges, cr angles, appears, 
in certain circumflances, to ilfue from all parts of that 
lurface equally. This fact, I apprehend, is fo well 
eifablilhed that it needs no further proof 
Now the column of quickfilver being confined 
.by the fides of the glafs, which are fuppofed par- 
allel, the top of the quickfilver will anfwer to 
the fmooth lurface defcribed. The eleCtric fluid 
therefore that is to pals from it, into the void fpace, 
which is of the fame diameter with the column of 
quickfilver, will move forward within the hollow 
of the tube to the next, column of quickfilver. 
And lince no refiflance is fuppofed to be within any 
part of the vacuum, there can be no caufe for any 
accumulation : confequently when the fluid is fuf- 
fered to pals along the tube, the appearance ought 
to be the fame at the furfaces, that it is in every 
part of the void fpace. But by my experiment 
there is a greater quantity of light feen at the le~ 
cond lurface of the quickfilver, than in any other 
part, (when polifhed glafs electrifies the firfl: co- 
lumn) and that this light which appears fo denfe, 
extends itfelf about one tenth of an inch from the 
furface. Whereas the light extending all along the 
intermediate hollow of the tube, appears to be 
much thinner, and rarer, and of an uniform 
denfity. I conclude therefore that this luminous 
accumulation at the fecond furface is caufed by a 
rejijlance exerted at, or near, the furface ol the 
quickfilver ; when the eledtric fluid, ifluing from 
