[ 641 ] 
Corollary. 
By the fame method of reafonfng, with the Jielp 
that if it appears, 
hat if AB and II each communicate with a third 
body, by canals of incomprethble fluid, and a com- 
munication is made between AB and H by another 
canal of incompreffible fluid, the fluid will have no 
tendency to flow from one to the other through this 
canal j fuppofing that the fluid was in equilibrio 
before this communication was made. In like 
manner if AB and H communicate with each other 
or each communicate with a third body, by canals of 
leal fluid, inftead of the imaginary canals of incom- 
prefhble fluid ufed in thefe propofitions, and a com- 
munication is alfo made between them by a canal of 
incompreflible fluid, the fluid can have no tendency 
to flow from one to the other. The truth of the 
latter part of this corollary will appear by fuppofing 
an imaginary canal of incompreffible fluid to be con- 
tinued through the whole length of the real one. 
P R' O P. XXV. 
Let now a communication be made between the 
two plates AB and DF, by the canal NRS of 
incompreffible fluid, of any length j and let the 
body H and the plate A B be overcharged. It 
is plain that the fluid will flow through that 
canal from A B to D F. Now the whole force 
with which the fluid in the canal is impelled 
VoL. LXI. 4 N along 
