1912. 



PUBLIC DOCUMENT — No. 31. 



117 



lain crucible, and the organic matter, water, etc., is driven off. 

 The sample is then cooled and weighed and loss of weight 

 recorded as " loss on ignition." It is then placed in a small 

 mortar and rubbed gently with a medium hard rubber-tipped 

 pestle to disintegrate the soil particles as far as possible. Then 

 the sample is sifted carefully with constant brushing with a stiff 

 camel's hair brush through 1-millimeter, .5-millimeter, .25-milli- 

 meter and .1-millimeter sieves, the last two being bolting cloth, 

 as in the long method. The residue remaining consists of the 

 very fine sand, the silts and clay. This remainder is weighed 

 and the weight recorded, and one gram or fraction thereof is 

 weighed out and used in the remainder of the process to deter- 

 mine the percentage of very fine sand, silts and clay. 



This determination is made in the following piece of appa- 

 ratus (see Fig. 1) : A is a circular test tube having a diameter 

 of approximately 2 centimeters and a length to the contraction 

 of about 7 centimeters; B is a flat glass tube with thin walls. 



\ / 



Fig. 1. — Showing special tube for mechanical analysis of soils: A, upper or circular part of the 

 tube; B, lower or flat part of the tube. The figures to the right show cross sections, etc., of 

 the tube. 



