THEORY OF THE EARTH. 29 



of trees, and plants growing near the sea, are en- 

 veloped in these aggregates ; and thus are pro- 

 duced what might he denominated indurated 

 downs, such as we see upon the coasts of New 

 Holland, and of which a precise idea may be 

 formed from the description given of them by 

 Peron *. 



Formation of Cliffs or Steep Shores. 



On the other hand, when the coast is high, the 

 sea, which is thus prevented from throwing up 

 any thing, exercises a destructive action upon it. 

 Its waves, by sapping the foundation, cause the 

 superincumbent portion of the face of the cliff, 

 thus deprived of support, to be incessantly falling 

 down in fragments. These fragments are tumbled 

 about by the billows, until the softer and more di- 

 vided parts disappear. The harder portions, from 

 being rolled in contrary directions, assume the 

 form of boulders and pebbles ; and these, at length, 

 accumulate in sufficient quantity to form a ram- 

 part, by which the bottom of the cliff is protected 

 against farther depredations. 



Such is the action of water upon the solid land ; 

 and we see, that it consists almost entirely in re- 

 ducing it to lower levels, but not indefinitely. 



* Voyage aux Terres Australes, t. i. p. 161. 



