LIST OF APPARATUS FOR EACH STUDENT. 



1 to 



The soils commonly used consist of a (1) sand, (2) loam, (3) silt, (4) 

 clay, and (5) peat. 



The sand is a white quartz of medium fineness. This is en- 

 tirely free from organic matter and of course represents an extreme. 

 A sand soil as taken from the field is occasionally used for purpose of 

 comparison. 



The loam is a mixture of sand (not over 50 percent) silt, clay and 

 organic matter. This represents a good type. 



The silt soil is one in which silt of different grades forms 70 per 

 cent or more of the constituents. It is a very common type of soil, 

 especially in glacial or loessial soil areas. The timber phase of this 

 type is used in the laboratory because it contains less organic matter 

 than the prairie phase. 



The clay soil used is a heavy, plastic, sticky, clayey soil, frequently 

 found in bottom lands along large streams. The samples used should 

 contain 30 percent or more of clay. 



The peat soil is obtained from peaty swamps or bogs, which are 

 especially common in north central United States. Organic matter 

 usually constitutes about 75 percent of this soil. (Where decomposi- 

 tion has gone on far enough and much clay is mixed with the organic 

 matter, muck soil is found.) 



The soils are prepared by being dried and pulverized until they 

 pass through a 2 millimeter sieve. 



M593629 



