on Rivers and Canals. 583 
great livers, although a large extent of their bed next the 
fea fhould be abfolutely horizontal, and without any de- 
clivity at all, yet their waters do not ceafe to flow, and to 
flow even with great rapidity, both from the impulfion 
of the back waters, and from the compreflion of the up- 
per waters upon the lower in the fame fedtion. 
30. Whoever is well acquainted with the principles 
of the higher geometry, will eafily perceive that it would 
be no difficult matter fo to dig the bed of a canal or ri- 
ver, that the velocity of the current Jhould be every where 
equal. It would be only giving it the form of a curve 
along which a moving body fhould recede from a given 
point, and defcribe /paces every where proportional to the 
times , allowance being made therein for the quantity of 
effedl of the compreflion of the tipper waters upon the 
lower. This curve is what is called the Horizontal Ifochronic , 
being the flatteft of an infinity of others which would 
equally anfwer the problem where fluids were not con- 
cerned. Upon thefe curves may be feen leibnitz, huyg- 
hens, and the two bernouilli’s, who were the firft that 
determined and analyfed them, and alfo many fucceed- 
ing geometricians, if any one is defirous to occupy him- 
felf in fuch fpeculations as are more curious than ufeful, 
which is not my purpofe in this treatife. 
4 G 2 ^ 31. Not- 
