Soil — Composition and Preparation 27 



where either clay or sand predominates. In the 

 case of clay, it helps to divide it, and in the case of 

 sandy soil, it helps toward retention of moisture. 



According to Tanner's "First Principles of 

 Agriculture" mineral soils may be divided into 

 five classes, according to their physical diflfer- 

 ences due to either of two principal ingredients — 

 clay and sand. The table given below explains 

 itself: — 



Name op Soil Pebcbntagb of Sand 



Sand 80 to 100 



Sandy Loam 60 to 80 



Loam 40 to 60 



Clay Loam (or "heavy" loam) . . . 20 to 40 



Clay to 20 



Therefore loam as we need it in the garden con- 

 tains about an equal amount of clay and sand. 



We can, of course, go very deeply into chemical 

 diflferences, but for the present it is sufficient to 

 know that soU may be "sour," and may be 

 "sweet." Either condition can easily be deter- 

 mined by placing litmus paper in the soil when 

 wet. If the paper turns pink the soil is sour, 

 if blue the soil is sweet. Peat and clay are 

 nearly always sour, owing to the fact that there 

 is little or no air in the soil, and thus acids 

 quickly form. 



