[ 629 •] 
of B on the fluid in D E, is equal to that of b on the 
fluid in de : therefore, taking ag to A zs af to 
AF, the repulfion of b on the fluid in ag^ is equal 
to that of B on the fluid in A^j but the repulflon 
of ^ on ag may be confidered as the fame as its 
repulflon on A ; for, by the fuppofition, the repiil- 
flon of B on A^ may be confldered as the fame as if 
it was continued infinitely j and therefore, the re- 
pulfion of b on ag may be confidered as the fame as 
if it was continued infinitely. 
N. B. If n was not greater than one, it would 
be impoflible for the length of A <3: to be fo 
great, that the repulfion of B on it might be 
confidered as the fame as if it was contioued 
infinitely j which was my reafon for requiring 
n to be greater than one. 
Corollary. 
By jufi the fame method of reafoning it appears, 
that if the bodies are undercharged, the quantity of 
deficient fluid in b will be to that in B, as af'~' to 
AF”"k 
PROP. XXI. ■ 
Let a thin flat plate be connected to any other 
body, as in the preceding propofition, by a 
canal of incompreffible fluid, perpendicular 
to the plane of the plate ^ and let that body 
be overcharged, the quantity of redundant, fluid 
in the plate will bear very nearly the lame 
3 proportion 
