THE EARTH. 141 



talk of their destruction ; and very few new ones 

 (if we except Mount Cenere, and one or two 

 such heaps of cinders) are produced. If moun- 

 tains, therefore, were of such great utility as some 

 philosophers make them to mankind, it would be 

 a very melancholy consideration that such benefits 

 were diminishing every day. But the truth is, 

 the valleys are fertilized by that earth which is 

 washed from their sides ; and the plains become 

 richer, in proportion as the mountains decay. 



CHAPTER XIII. 



OF WATER. 



IN contemplating nature, we shall often find the 

 same substances possessed of contrary qualities, 

 and producing opposite effects. Air, which li- 

 quefies one substance, dries up another. That 

 fire which is seen to burn up the desert, is often 

 found, in other places, to assist the luxuriance of 

 vegetation ; and water, which, next to fire, is the 

 most fluid substance upon earth, nevertheless 

 gives all other bodies their firmness and dura- 

 bility ; so that every element seems to be a power- 

 ful servant, capable either of good or ill, and only 

 awaiting external direction, to become the friend 

 or the enemy of mankind. These opposite quali- 

 ties, in this substance in particular, have not fail- 

 ed to excite the admiration and inquiry of the 

 curious. 



