PHYSICAL COMPOSITION AND CLASSES OF SOILS 



Si 



Method of the Bureau of Soils. 1 The following is an outline 

 of the method of mechanical analysis of soils used by the Bureau 

 of Soils. Five grams of soil are shaken for six hours or longer 



Fig. 25. Centrifugal machine used in mechanical analysis of soils. 



with water containing a little ammonia, in order to decompose the 

 compound particles. The soil is then washed into a centrifugal 

 tube, and the centrifugal machine run at full speed for about 

 1 Bulletin 24, and Bulletin 84. 



