VEGETABLE SOIL DIAGBAM 19 233 



Vegetable earths may be classed in four principal groups : 



1st Sandy soils. 



2nd. Clayey soils. 



3rd. Calcareous soils. 



4th. Peaty soils. 



1st. Sandy soils are chiefly composed of gravel or of sanci, 

 which is sometimes very fine, and does not retain water ; these 

 soils are liable to drought. Such soils are generally found on 

 the shores of the sea, or of rivers. "When mixed with a large 

 proportion of decaying vegetable matter, the sandy soils form 

 heath-soil, which may be rendered very productive by abundant 

 watering or manuring. 



2nd. The clayey earths are those where clay predominates, and 

 agriculturists generally call them stiff, or heavy soils. They are 

 often of a reddish colour, and may even be recognised at a dis- 

 tance by their appearance. When mixed with water, they form 

 a kind of stiff paste. Clayey soils are nearly impervious to 

 water; if sloping, they are easily cultivated, and yield large re- 

 turns, but if they cover a flat country, the water cannot run off, 

 but accumulates at the surface, and the vegetation is to some ex- 

 tent drowned. Then, when warm weather returns, the soil 

 hardens, cracks, and thus tears the roots of the plants. 



On the other hand, when clayey soils contain a proper propor- 

 tion of sand or lime, they are excellent for agricultural pur- 

 poses. 



3rd. Calcareous soils are those which are formed by the decom- 

 position of calcareous strata. When there is too much lime, the 

 quality of the land is bad like clayey soils which contain too 

 much clay, or sandy soils which contain too much sand. When 

 there is too much lime in the soil, the surface, when moistened, 

 cakes, and forms a crust which prevents the air from penetrating 

 into the ground. Frost loosens the chalky soil, pulverises it, 

 and in this condition the earth is sometimes carried away by the 

 wind, and leaves the plants uncovered, and without proper sup- 

 port for the roots. 



But in most cases, calcareous soils contain more or less sili- 



