174 HISTORY OF 



remain without any further mutation. And it is 

 happy for man that bounds are thus put to the 

 erosion of the earth by water ; and that we find 

 all rivers only dig and widen themselves but to a 

 certain degree.* 



In those plains t and large valleys where great 

 rivers flow, the bed of the river is usually lower 

 than any part of the valley. But it often hap- 

 pens that the surface of the water is higher than 

 many of the grounds that are adjacent to the 

 banks of the stream. If, after inundations, we 

 take a view of some rivers, we shall find their 

 banks appear above water, at a time that all the 

 adjacent valley is overflown. This proceeds from 

 the frequent deposition of mud, and such like 

 substances, upon the banks, by the rivers fre- 

 quently overflowing ; and thus, by degree, they 

 become elevated above the plain ; and. the water 

 is often seen higher also. 



Rivers, as every body has seen, are always 

 broadest at the mouth, and grow narrower to- 

 wards their source. But what is less known, and 

 probably more deserving curiosity, is, that they 

 run in a more direct channel as they immediately 

 leave their sources, and that their sinuosities and 

 turnings become more numerous as they proceed. 

 It is a certain sign among the savages of North 

 America, that they are near the sea, when they 

 find the rivers winding, and every now and then 

 changing their direction. And this is even now 

 become an indication to the Europeans thenv 



* Guglielmini della Natura de Fiumi, passim. 

 f Buffon, De Fleuves, passim? vol. ii. 



