f 627 ] 
IS impelled with any given force Jn the dire6Hon of 
the canal at that place, the fedion D d would, in 
confequence thereof, be impelled with exadly the 
fame force in the diredion of the canal at D, if the 
fluid between E ^ and D ^ was not at all attraded or 
repelled by the two bodies ; and, confequently, the 
fedion D is impelled in the diredion of the canal, 
with the fum of the forces, with which the fluid in 
each part of the canal is impelled, by the attradion 
or repuUion of the two bodies in the diredion of the 
axis in that part j and confequently, unlefs this fum 
was nothing, the fluid in D ^ could not be at reft. 
Corollary. 
Therefore, the force with which the fluid in the 
canal is impelled one way in the diredion of the axis, 
by the body B, muft be equal to that with which it 
impelled by b in the contrary diredion. 
P R O P. XX. 
Let two fimllar bodies B and ^ ( fig. r 3 .) be conneded 
by the very flender cylindric or prifmatic ca- 
nal A filled with incomprefiible fluid, in the 
fame manner as defcribed in the preceding pro- 
pofition ; let the bodies be overcharged j but 
let the quantity of redundant fluid in each bear 
fo fmall a proportion to the whole, that the 
fluid may be confidered as difpofed in a fimilar 
manner in both j let the bodies alfo be fimilarly 
fituated in refped of the canal A^j and let 
them be placed at an infinite diftance from each 
4 L a other, 
