KINDS OF SOIL 73 



should shrink considerably in bulk and in weight 

 by burning. 



Separating the Sand, Silt and Clay. After the 

 humus is burned out of this soil the sand, silt and 

 clay remain. These being pieces of rocks, or 

 mineral matter, they will not burn like humus, 

 which is vegetable matter. A simple way to 

 separate the three ingredients is to put the soil into 

 a tall, wide-mouthed bottle; one holding two 

 quarts will answer, but a larger one is better. Fill 

 this full of water and shake it violently until all the 

 soil is mixed with water. Stand it on the table and 

 watch the soil settle. If the soil contains coarse 

 sand this will settle almost immediately, being 

 largest and heaviest. Medium sand and fine sand 

 will settle more slowly. Part of the silt and clay 

 will remain suspended in the water for many hours. 

 After several days, or when the water is clear, all 

 the soil will be deposited in the bottom of the jar; 

 the sands on the bottom, then silt, and clay on top. 

 These ingredients may not be deposited in well- 

 defined layers, because sand, silt and clay are ar- 

 bitrary terms, used to designate soil grains of cer- 

 tain abitrary sizes, for the sake of convenience in 

 describing them. In some cases the sand may 

 grade into the silt and the silt into clay impercep- 

 tibly; in other cases ill-defined layers can be seen. 

 In any case a close scrutiny of the way in which the 

 soil settles and of its appearance after it settles will 

 enable one to estimate roughly the proportions of 

 sand, silt, and clay that it contains. 



It will pay a farmer to test the different types of 

 soil on his farm in this way, and especially to test 

 several different soils at the same time and com- 

 pare them. The results of these simple experi- 

 ments will bear out and emphasise field observa- 



