[ 665 3 
knobs on It, or is otherwife formed in fuch manner 
as to make the ele<ftricity efcape fafter from fome 
parts of it than the reft. 
In like manner, if the body ABD be under- 
charged, the air adjoining to it will alfo be under- 
charged, and will therefore be repelled by it; but as 
the air dole to the end of the point will be more 
nndert barged than that ciofe to the reft of the body, 
it will be repelled with much more force ; W'hich 
will caufe exadly the fame current of air, flowing 
the fame way, as if the body was overcharged; and 
confequently the velocity with which the electric 
fluid flows into the body, will be very much increafed. 
1 believe indeed that it may be laid down as a con- 
ftant rule, that the fafter the eledtric fluid efcapes 
from any body when overcharged, the fafter will it 
run into that body when undercharged. 
Points are not the only bodies which caufe a quick 
difcharge of eledtricity ; in particular, it efcapes very 
faft from the ends of long ftender cylinders; and a 
fwift current of air is caufed to flow from the middlie 
of the cylinder towards the end : this will eafily ap- 
pear by confidering that the redundant fluid is col- 
ledled in much greater quantity near the ends of the 
cylinders than near the middle. The fmis thing 
may be faid, but 1 believe in a lefs degree, of the 
edges of thin plates. 
What has been juft faid concerning the current of 
air, ferves to explain the reafon of the revolving 
motion of Dr. Hamilton’s and Mr. Kinnerfley’s bent 
pointed wires, vide Phil. Tranf. voi. LI, p. 905, and 
vol. LIII, p. 86; alfo Prieftly, p. 429: for the lamere- 
pulflon which impels the air Ifom the thick part of the 
VoL. LXI, 4 wire 
