154 HOW CROPS FEED. 
of fertility and barrenness, and covering a wide range of 
variety as regards composition. It is therefore qualified 
by various epithets, as coarse, fine, etc. Coarse, sandy 
soils are usually unprofitable, while fine, sandy soils are 
often valuable. 
' 
Clayey Soils are those in which clay or impalpable mat- 
ters predominate. They 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 shrinking 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 adhesiveness and impermeability to 
water which usually characterize clay, without containing 
those compounds (kaolinite and 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 soca 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 impalpable matters. They are free 
from the excessive tenacity 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: 
