SOILS AND FERTILIZERS 



been passed through a sieve with holes 0.5 mm. in diameter are 

 placed in a mortar and about 20 cc. of water added. The soil is 

 pestled with a rubber-tipped pestle with the object of separating 

 adhering particles without pulverizing the individual soil grains. 

 After two or three minutes' pestling, more water is added and the 

 soil and water are allowed to sediment for about one minute ; the 

 turbid liquid is then decanted into a beaker. This process of soft 



pestling and decan- 

 tation is repeated 

 two or three times 

 until the remaining 

 soil grains appear 

 free from adhering 

 smaller particles. 

 With some soils 

 this is a tedious 

 process. The con- 

 tents of the mortar 

 are then transferred 

 to the beaker and 



enough water added 

 FIG. 57. The Mechanical Analysis of Soils. to near ] v fi\\ ^ Q 



beaker. The contents of the beaker, are thoroughly stirred, and after 

 two or three minutes 1 sedimentation, the turbid liquid is decanted 

 into a second beaker, leaving the sediment in the first beaker. More 

 water is added to the first beaker, and the stirring, sedimentation, 

 and decantation are repeated until the sediment consists mainly of 

 -clean fine sand. After about ten minutes the turbid liquid in the 

 second beaker is decanted into a large cylinder, the sediment in the 

 beaker being washed with more water and the washings added to the 

 cylinder. It is to be noted that the sediment in the second beaker 

 is composed of finer particles than the sediment in the first beaker. 

 The sediment in the first beaker consists mainly of medium and fine 

 sand, and in the second beaker of fine sand and coarse silt. Some 



