Sect. I. Agriculture and Vegetation. 47 



ART often imitates nature in this me- 

 thod of improving land, and lets in the 

 ftreams of rivers to cover the fields. This 

 is moft frequently done in the fpring, when 

 thefe waters are moft impregnated with 

 nutritive particles. This water, after it has 

 depofited all its particles, which it does in 

 four or five days, is let off quickly ; left, 

 by a gradual evaporation, it fhould cake the 

 ground, and hinder the grafs to come up ; 

 which is the great danger attending it, and 

 for which it is thought improper for clay 

 grounds. 



IT muft be obferved here, that there 

 are fome waters which are extremely preju- 

 dicial to grounds, fuch as coal and fteel 

 waters. This is owing to the quantity of 

 iron which both thefe contain. All fulphur 

 waters are likewife hurtful to ground ; we 

 fhall afterwards fee that fulphur is a poifon 

 to plants, 



SECT. 



