46 The Principles of Part II. 



exceedingly fertile. Spring-water is even 

 found to be of fervice to ground, but not 

 fb much as river-water, especially fuch as 

 has run through a fertile country, and is, 

 at that time, full of the fubtiler particles 

 of the .foil warned off from the rich grounds 

 by rains. As thefe waters are impregnated 

 with the fubtile earth, and the faponaceous 

 juices of thofe foils over which they have 

 run, when they ftagnate, thefe nutritious 

 particles fubfide, and inrich the ground. 

 The river Nile depolites a rich oozy mud, 

 which is fo full of putrefcent particles, that 

 its fleams feem to be the caufe of the 

 plague raging fo much in Egypt. By this 

 addition of foil it receives every year, the 

 level of the ground is confiderably higher 

 than it was. Hence too the vallies in all 

 countries are much richer than the rifing 

 grounds ; as the rains warn great part of the 

 vegetable matter from the latter, and leave 

 it in the former. 



ART 



