154 ItOW CROPS FEED. 



of feitility and barrenness, and covering a wide range of 

 variety as regards composition. It is therefore qualitied 

 by various epithets, as coarse, fine, etc. Coarse, sandy 

 soils are usually unprofitable, while fine, sandy soils are 

 often valuable. 



('layey Soils are those in wliicli clay or impalpable mat- 

 ters predominate. Tliey are commonly characterized by 

 extreme fineness of texture, and by great retentive power 

 for water ; this liquid finding passage through their pores 

 with extreme slowness. When dried, they become crack- 

 ed and rifted in every direction from the shi-inking that 

 takes place in this process. 



It should be distinctly understood that a soil may be 

 clayey without being clay, i. e., it may have the external, 

 physical properties of ndhesiveness and impertneability to 

 water which usually characterize clay, without containing 

 those compounds (kaolinite ami the like) which constitute 

 clay in the true chemical sense. 



On the other hand it were possible to have a soil consist- 

 ing chemically of clay, which should have the physical 

 properties of sand; for kaolinite has been found in crys- 

 tals jo'oo of an inch in breadth, and destitute of all cohesive- 

 ness or plasticity. Kaolinite in such a coarse form is, how- 

 ever, extremely rare, and not likely to exist in the soil. 



Loamy Soils are those intermediate in character between 

 sandy and clayey, and consist of mixtures of sand with 

 clay, or of coarse with impal{)able matters. They are free 

 from the excessive tenacit}' of clay, as well as from the too 

 great porosity of sand. 



The gradations between sandy and clayey soils are 

 roughly expressed by such terms and distinctions as the 

 following : 



