on Rivers and Canals. 
619 
SECTION II. 
Laws of the meeting of oppojite currents , with the appli - 
cation of them to Jluices. 
53. When two equal currents of homogeneous fluids 
meet in oppofite directions, there is firft a iwelling and 
rifing up of them at the point of rencounter; then 
follows a revulfion and counter current of each equally 
back again, fo as to bring the whole to an equilibrium. 
54. If the two oppofite currents are unequal, either in 
force or in quantity, or in both, there will ftill be a fwel- 
ling and revulfion of each back again, but it will be 
diminilhed in the greater current, and augmented in the 
lefler, by the quantity by the which the one furpafles 
the other; and the point of rencounter of the two cur- 
rents will have a flow and progreflive motion in the di- 
rection of the ftronger, the degree of velocity thereof 
being always in a direCt ratio of the force and quantity 
of the one above the other, 
55. If the fluids in oppofite currents be not homoge- 
neous, as is the cafe between fea and river water, that 
which has the leaft fpecific gravity will fwim upon the 
other, and continue to follow its firft direction, until 
