on Rivers and Canals. 
579 
water of that foie part of the current where it remains 
fufpended. 
It is very eafy to guide both the cylinder and the globe 
in that part which we want to meafure, by means of two 
threads or fmail cords, which two perfons muft hold and 
direct, one on each fide the river; taking care at the fame 
time neither to retard nor accelerate the motion of the 
inftrument. 
Several other methods have been invented for deter- 
mining the velocity of the currents of rivers and canals^ 
which may be feen in moft of the authors enumerated- 
in the beginning of this elfay (N° a.) 
IV. application of the preceding laws of the acceleration 
and retardation of currents to rivers and canals in ge- 
neral, from whence are deduced the various means of 
preventing or remedying the defeSls and inconveniencies' 
which mujl neceffarily happen to them in a feries of 
years 
27. By combining together all we have laid hitherto* 
upon the nature and theory of motion in rivers, and par- 
ticularly in the articles 13. 18. 20. 21. and 23 .it follows 
evidently, that the deeper the waters are in their bed 
in proportion to its breadth , the more their motion is ac- 
celerated f 
