[ 643 ] 
If the canal hy is of fo great a length, that the 
repulfion of h thereon is the fame as if it was con- 
tinued infinitely, then the thing is evident : but if it 
IS not, et the canal hy^ inftead of communicating 
with xy IS, fo that the fluid can flow out of the canal 
into xy z, be continued infinitely through its fub- 
Irance, along the linejji'u : now it mufl; be obferved 
that a fmall part of the body namely, that 
which IS turned towards h, will by the adion of upon 
It, be rendered undercharged ; but all the refl: of 
the body will be faturated ; for the fluid driven out 
of the undercharged part will not make the re- 
mainder, which is fuppofed to be of an infinite fize, 
fenfibly overcharged : now the force with which the 
fluid in the infinite canal hyv, is impelled by the 
body ^ and the undercharged part oi xy%, is the 
fame with which the fluid in is impelled by them; 
but as the fluid in all parts of xyx is in equilibrio, 
a particle in any part ofyv cannot be impelled in 
any diredion ; and therefore the fluid in by is im- 
pelled with as much force as that inhyv, and there- 
fore the fluid in by is impelled with as much force 
as that in ^ c ; and is therefore impelled with as much 
force as the fluid in N R S is impelled by the two 
plates. 
It perhaps may be afked, whether this method of 
demonftration would not equally tend to prove that 
the fluid in by was impelled with the fame force as 
that in N R S, though xyz did not contain juft fluid 
enough to faturate it. I anfwer not; for this de- 
monftiation depends on the canal yv being continu- 
ed, within the body xyz^ to an infinite diftance 
beyond any over or undercharged part ; which could 
4 N 2 not 
