1 86 the Principles of Part V. 



4, No plants can grow without a fuffi- 

 cient quantity of frefh air, which is as ne- 

 ceflary to the vegetable life as to the animal. 

 Whatever plants cover the ground clofely, 

 deftroy all thofe which grow below. Hence 

 a good crop of peafe kills all weeds by 

 overshadowing them ; in fo much that the 

 farmer aflures himfelf of a good crop of 

 wheat if the peafe are good. If they are 

 not, a greater quantity of weeds comes up 

 than ufual; and he never can expedl any 

 of the three following crops to be good, 

 wnlefs he gives the ground a fallowing. 



. IT is in this way, likewife, that fog is 

 deftroyed. The inclpfure is fhut up from 

 the middle of May to the beginning of De~ 

 cember, and then fed from that time to April, 

 After that it is faved for a crop of hay. The 

 fog being fo long covered by two fucceeding 

 crops of grafs, is cut off from the benefit of 

 the air, and fo di-es., 



5. THERE 



