THE SOIL PARTICLE 



97 



4 in England, and in Continental Europe, respectively. 

 As to which is the best for an interpretation and ex- 

 pression of textural qualities it is difficult to say. They 

 are all arbitrary, yet they are all extremely useful. 

 It therefore seems immaterial which one is employed. 

 It would be better, of course, if the classification were 

 uniform for all countries; correlation of soil properties 

 would then be easier. 



72. Bureau of Soils classification. — As the grouping 

 established by the United States Bureau of Soils is met 

 with in all of our soil literature, and as it is really the 

 standard classification for this country, a closer considera- 

 tion of it may be profitable. The discussion of the 

 properties exhibited by the various separates, and of the 

 interpretation and value of a mechanical analysis, will 

 therefore be made with this classification as a basis. By 

 way of illustrating the grouping and the mode of ex- 

 pressing a mechanical analysis the results obtained from 

 two distinctly different soils are given below : — 



Mechanical Analyses l of a Dunkirk Fine Sandy Loam 

 and a Dunkirk Clay 



Separate 



Fine gravel . 

 Coarse sand . 

 Medium sand 

 Fine sand 

 Very fine sand 

 Silt . . . 

 Clay . . . 



Size in 

 Millimeters 



2-1 



1-.5 



.5-.25 



.25-. 10 



.10-.05 



.05-.005 



below .005 



Fine Sandy 

 Loam 



% 

 1 



2 



3 



22 



35 



27 

 10 



% 

 1 

 2 

 2 

 6 

 7 

 39 

 43 



1 Soil Survey Field Book, pp. 152, 154. U. S. D. A., Bur. 

 Soils. 1906. 



