on Rivers and Canals. 573 
place, compared to that in another, is in a compound ratio 
of the mafs of water and of the velocity of the current 
in thofe places refpedtively. 
24. In different parts of the fame river, the velocity 
of the current is greater in a diredt proportion of the 
greater declivity of the bed ; becaufe the relative gravity 
of the flowing particles augments in that ratio. 
25. But in the fame fection of a river, the fuperior 
parts, and thofe which are farthefl from the bottom and 
the fides, will continue their courfe by the foie caufe of 
the declivity of their bed, how little foever it be ; becaufe 
thefe waters not being retarded by the fridfion of the 
bottom and fides of the bed, or hardly by any other ob- 
ftacle whatever, the leajl pofible deviation from a level 
will produce a current. But the waters at the bottom of 
a river, both becaufe of their fridtion againft it, and of 
the irregularities which are almofl every where found in 
it, will lofe that little motion which a very fmall declivity 
can give them, and their motion in that cafe will be pro- 
duced alone by the compreffion of the fuperior waters 
upon them. 
The inferior waters which thus acquire their motion 
from the weight of the fuperior ones upon them, com- 
municate reciprocally a part of their motion, by means 
of the natural cohefion of the particles together (N° 20.) 
4 F a to 
