SOIL FORMATIONS AND CLASSIFICATIONS 57 



The soil strata are commonly classed as top soil and subsoil, and 

 in the name of a soil type the character of the top soil is indicated, 

 and also that of the subsoil if it is peculiar or markedly different 

 from the top soil. In the detail soil survey of Illinois conducted 

 by the State Experiment Station, which now covers about thirty 

 counties, or one third of the state, the preceding soil types have 

 been recognized and mapped, and records are kept under the 

 numbers and names given. 



The system of numbering (similar to the Dewey library system) 

 is flexible, and permits additions of main types or related types 

 (by decimals), and the name is designed to carry with it a definite 

 suggestion of the character of the soil. 



