THE SOIL PARTICLE 



85 



by the Second International Agro-Geological Congress, 

 which met in Stockholm in 1910. In simplicity and 

 facility of interpretation the last-named grouping seems 

 at least equal to that of the Bureau of Soils. Since a 

 number of methods of mechanical analysis have been 

 devised during the evolution and study of soil separation, 

 it is necessary to be conversant with the principles in- 

 volved and with at least two or three of the most successful 

 modes of procedure. 



64. Principles of mechanical analysis. — The various 

 methods of mechanical analysis may be grouped according 

 to the agents employed in the separation. The outline is 

 as follows : — 



1. Sieve 



Outline of systems of mechanical analysis 



Wet 



(Used to separate sands in practically all 



j) methods) 



3. Water 



In motion 



At rest 



2. Air (Cushman's air elutriator) 



Gravity (Schone's elutriator and 



Hilgard's churn elutriator) 

 Centrifugal (Yoder's centrifugal 



elutriator) 

 Gravity (Osborne's beaker method 



and Atterberg's modified silt 



cylinder) 

 Centrifugal (Bureau of Soils 



method) 



In the consideration of such an outline, certain of the 

 general methods proposed may be dismissed without 

 further parley since they are inadequate for the separation 



