EXERCISE A-3. TO STUDY THE GROUPS OF INDI- 

 VIDUAL SOIL PARTICLES. 



Equipment: Four beakers or tumblers; samples of 

 clay and sandy soil. 



Method: Make fine and dry a small quantity of 

 ^ach of the two kinds of soil. Put three tablespoonfuls 

 of the clay soil in one tumbler or beaker, and a like amount 

 of the sandy soil in the other. Fill each one half full 

 with water. Taking the tumblers or beakers one at a 

 time, proceed as follows: shake genth^ for four minutes, 

 let stand one minute and pour off into another tumbler 

 all the water possible without losing the setthngs. The 

 settlings are the sand. Allow the water poured off to 

 stand one hour until a distinct laj^er of settlings can be 

 seen at the bottom. Now pour off and discard the clouded 

 water. This nmddy water contains clay so fine that it will 

 not settle. The material which has settled in the second 

 glass is silt. 



Questions: (1) About what proportion of the sandy 



soil is silt? 



(2) About what proportion of the clay soil is silt? 



Discussion: Soils are classified according to the fine- 

 ness of the rock particles which they contain. A soil 

 which contains a large proportion of coarse particles is 

 called a sandy soil. One which contains a large })ropor- 

 tion of fine particles is called a clay soil. No soil is made 



6 



