C 3 6 9 ] 
How much foever the vacuum, here made ufe of, 
>inay exceed that, which is ufuaily arrived at, it is far from 
being a perfect one ; and to make one more fo, ex- 
cept that of Torricelli, which cannot without difficulty 
be applied to the prefent purpofe, is not very eafy. 
But it appears from the already mentioned experi- 
ments, as well as from a fubfequent one, that the vacu- 
um, which we are mailers of, does not tranfmit the 
electricity fo perfectly as metals and water ; as we are 
able to draw fnaps from the prime conductor, an ar- 
gument of fome degree of accumulation, while the 
electricity is palling through the vacuum. This never 
happens, when metals, handing upon the ground, 
touch the prime conductor. As we obferve therefore, 
that the corufcations diverge more or lefs, in propor- 
tion as there is more or lefs air left in the tube, this 
effect may arife even from the ftnall quantity of air 
hill remaining undifcharged, 
I was delirous of knowing, for the farther illuf- 
tration of my proportions, whether the experiment 
of Leyden could be made through the vacuum. For 
this purpofe I made the before -mention’d exhauhed 
tube part of the circuit, fo necelfary to this experi- 
ment. What this circuit is, I have in my former 
communications fo often and fo clearly exemplified, 
that it would be needlefs to repeat it here. You 
know in this experiment it is likewife abfolutely nc- 
celfary, that the whole quantity, or nearly fo, of the 
accumulated electricity lliould be difcharged in the 
fame inftant of time. Accordingly, upon making 
the experiment, at the inftant of the explolion, you 
faw a mafs of very bright embodied lire jump from 
one of the brafs plates in the tube to the other : but 
this did not take place, when one of the plates was 
A a a farther 
