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SOIL PHYSICS AND MANAGEMENT 



Different Systems of Physical Analysis, with the Grades and Ratio or Factor 



Between Grades l 



1. Methods of Mechanical or Physical Analysis. (a) The 

 Sieve Method. The sieve method is used as a part of practically 

 every system for the separation of gravel and some or all grades 

 of sand. It consists of using sieves with openings of the required 

 size for making the necessary separation. The separations may 

 be made dry or by. washing the material through with water. The 

 latter is preferable. 



(b) The Subsidence Method. The soil to be analyzed is 

 thoroughly disintegrated by shaking with water containing a few 

 drops of ammonia. It is then passed through a battery of sieves 

 to remove the sand and gravel. The water with the fine material in 

 suspension is then placed in a wide-mouthed bottle and the finer 

 grades are decanted first. This is accomplished by filling the bottle 

 such as shown in figure G5 to a certain mark with water and allow- 

 ing it to stand sufficiently long for the coarser grades to settle below 

 the mouth of the tube. The supernatant liquid with its grade of 

 soil particles is then blown off through the tube B by forcing air 

 through the tube A. The contents of the bottle are stirred and 

 sufficient time is allowed for the coarser particles to subside again. 

 As the sands tend to carry the fine material down with them this 

 operation must be repeated several times. The same thing is done 

 for each of the other grades. The microscope is used to determine 

 whether the proper size is being removed. The great amount of 

 time required is a serious objection to this method. 



(c) Schone's Elutriator Method. 2 The method of separating 

 soil particles by currents of water of varying velocities was first 



