48 THEORY OP THE EARTH. 



by great rains, they undermine the bottoms of 

 the earthy or sandy hills which lie in their way, 

 and carry their fragments to be deposited on the 

 lower grounds which they inundate, and which are 

 somewhat raised in height by each successive in- 

 undation. Finally, when these rivers reach the 

 great lakes, or the sea, and when of course that 

 rapid motion by which they are enabled to keep 

 the particles of mud in suspension has wholly 

 ceased, these particles are deposited at each side 

 of their mouths, where they form low grounds, by 

 which the coasts or banks of the river are gradual- 

 ly lengthened out into the sea or lake. And if 

 these new coasts are so situated that the sea also 

 throws up sand to contribute towards their in- 

 crease, provinces, and even entire kingdoms, are 

 thus as it were created, which usually become the 

 richest and most fertile regions, if their rulers per- 

 mit human industry to exert itself in peace. 



11. Of the Formation of Downs* 



The effects produced by the sea alone, without 

 the aid of rivers, are far less beneficial. When 

 the sea coast is low, and the bottom consists of 

 sand, the waves push this sand towards the shore, 

 where, at every reflux of the tide, it becomes par- 

 tially dried ; and the winds, which almost always 

 blow from the sea, drift up some portion of it upon 



* Note G, 



