58 The Sugar-Beet in America 
kinds: those that overlie the rock from which they were 
formed, and those formed in place largely by the accumu- 
lation of organic matter, as in swamps. Transported soils 
vary with the agent used in carrying the materials of which 
they are composed. Those transported, by running water 
are called alluvial; by ice, glacial; by wind, eolian; 
and by the ocean, marine. Each of these kinds of soils 
has its own peculiar properties, although the composition 
is dependent largely on the rock from which it is formed. 
Probably more sugar-beets are raised on the alluvial soils 
than on any other group, although good beet sections are 
found on all the groups. 
In addition to classification according to origin, soils 
are sometimes classified by their chemical composition, 
by the native vegetation growing on them, by the crops 
to which they are suited, by the size of particles com- 
posing them, and by a number of other properties. For 
our purpose the classification according to the crop adap- 
tation is probably most interesting. 
SOIL AND SUBSOIL 
(Plates VI and VII) 
For practical purposes, the soil layer is divided into 
the surface soil and subsoil, the subsoil being the part 
below the plowed zone. Soils vary greatly in their general 
make-up; some are but a few inches deep and overlie 
rock, whereas others are hundreds of feet deep and fairly 
uniform throughout. Every gradation between these two 
is found, including clay surface soil with gravelly subsoil 
or gravelly surface with clay below. In arid regions the 
