102 THE FERTILITY OF THE SOIL [CH. 



to cultivated sands and finally end in sand wastes, 

 and find all the way gradual transitions with never 

 a break to mark off the different classes of soils. 

 A typical sandy soil is just as characteristic as a 

 typical clay, but it equally defies rigid definition. 



In many respects sand is the opposite of clay in 

 general properties. Sandy soils have little power of 

 holding water and therefore dry very readily ; they do 

 not long remain wet even after heavy rainfall. They 

 are not sticky. The rock from which they are formed 

 is generally somewhat hard, and so it has often hap- 

 pened that they have suffered less erosion than the 

 clays, and have not, like the clays, been hollowed out 

 into broad valleys. The ease with which water per- 

 colates through sand has led to the washing out of 

 much of the soluble material, so that little is left 

 except hard insoluble mineral grains which furnish 

 but scanty food for plants. 



Agriculturally the sands are a very mixed group. 

 Their small power of retaining water is a serious 

 disadvantage, partly because they become liable to 

 drought, and partly also because of the ease with 

 which manurial substances are washed away and 

 lost. A good many of these soils happen to lie in 

 relatively low situations and to receive underground 

 water from the land above; these are often suffi- 

 ciently supplied with water for all crop purposes. 

 Others lie rather too high to enable the underground 



