Sed. III. Agriculture and Vegetation. 163 



fprig of mint, which has fome roots in 

 water, and fome in earth, will, according 

 to 7#//'s experiment, moiften the earth 

 from its roots. The liguminous plants, by 

 covering the foil, keep it moift, hinder the 

 fun to confblidate it, and deftroy the weeds 

 which help fo much to bind it. Hence the 

 reafon why a change of fpecies meliorates 

 the foil fo much. When the ground is 

 often fowed with white grain, it turns ftiff. 

 A crop of peafe, beans, or clover, pulve- 



rizes it again. 



FA R M E R s have difcovered, by expe- 

 rience, that all the fibrous-rooted plants 

 impoverish the ground, and do not thrive 

 when they fucceed one another ; while the 

 carrot-rooted enrich the foil, and may fol- 

 low one another with fuccefs. The latter, 

 by opening the ground, make the influ- 

 ence of the air on it reach deeper, and con- 

 fequently help to produce more of the ve- 

 getable food ; while the former, by conib- 

 lidating the ground, fhut out in a great 

 '". M 2 mea- 



