62 



AGRICULTURE 



loam" are especially suited. Peanuts, sweet-potatoes, 

 cowpeas, and watermelons are good crops for sandy soils. 

 Best uses for clay soils. Since clay soils contain so 

 much water, they are slow in warming in the spring. Vou 

 know that if you dip your hand in water, even in rather 



From Fletcher's " Soils." Doubleday, Page & Co. 



FIG. 42. A HILLSIDE TOO STEEP FOR CULTIVATION 

 It should be used for pasture or forest. 



warm water, and then expose it to the air, the skin becomes 

 cool. This is because evaporation of water (that is, the 

 changing of water from a liquid into the form of a gas or 

 water vapor) has required heat and has drawn this heat 

 from the skin. In a stiff clay soil much of the water must 

 be evaporated from the surface. This uses the heat that 

 ought to be used in warming the soil. Hence a clay soil 

 is a cold soil, and crops growing in it start late. 



