76 ARRANGEMENT OF CHEMICAL PRINCIPLES. 



brought ill contact with calcareous, carbona- 

 ceous, and metallic substances, and also with 

 water, and by these absorbed or decomposed. 



Conformably to the preceding doctrines, the 

 cultivation of land, naturally is divided into 

 two important operations, — viz. 



First, The adapting, improving, or correcting 

 the surface of the earth, and the sub-soil, that it 

 may receive and regulate a due supply of water, 

 and afford a proper accommodation for the roots 

 of vegetables. 



Secondly, The regulating and furnishing the 

 needful supply of food for such plants, and for 

 such purposes as it may be desirous to cultivate ; 

 or to furnish such plants as the soil is best 

 adapted to support. 



To be enabled to form a correct judgment on 

 these points, it will be necessary, first, to com- 

 prehend the nature and properties of the roots of 

 plants, and also of theii' stalks, branches, and 

 leaves. 



