80 



NATURE AND PROPERTIES OF SOILS 



but at the same time will name it in such a manner as to reveal 

 its general physical peculiarities and proportions. For this 

 class names, such as sandy loam, loam, silt loam, and the 

 like, are used. Class differs from texture, however, in that it 

 has reference to the properties exhibited by a soil rather than 



_G RAVEL 5ANb LOAN CLAY 



f e>- 



// SSSSS/s 



/ Ss 



Fig. 16. — Diagram showing in a general way the mechanical compo- 

 sition of gravel, sand, loam and clay soils and indicating in addi- 

 tion how some of the more common field names arise. 



to any absolute grain size. Consequently, there may be a 

 number of class names depending on the proportionate mix- 

 tures of different sized particles that occur in the field. 



Class names have originated through long centuries of agri- 

 cultural observations, but of late they have been more or less 

 standardized because of the necessity of a definite nomen- 

 clature. In general, the names used for the soil classes are the 



