SOILS THEIR CHARACTERISTICS. 



21 



greasiness to the feel, caused by the predominance of the 

 clay in them. They are difficult to work, and in dry 

 weather bake like brick and are not permeable to light 

 dews and rains. In drying, they crack, exposing, in sum- 

 mer, the large roots of plants to the air and sun, and 

 breaking the smaller ones. After heavy rains they become 

 so saturated that they are for a long time unfit to work, 

 and the plants therein die from excess of moisture. In 

 short, they are very cold when they are wet, and very 

 hard when they are dry. The crops are full ten days later 

 in coming to maturity, than in a good, sandy loam. Or- 

 dinary clays contain about twenty-five per cent of sand. 

 If less than fifteen per cent, they are only fit for brick- 

 making and pottery. 



Clays are rich in alkalies, and have the property of re- 

 taining potash, phosphoric and silicic acids, and all salts 

 necessary to the growth of plants ; also of condensing am- 

 monia and other gaseous matters. Hence they retain the 

 virtues of manure better than most other soils. Where 

 there is present lime and organic matters in sufficient 

 quantity, clays, not too stiff, are excellent for wheat. 



A Sandy Soil is in texture the opposite of the preced- 

 ing and the lightest of all soils. . It contains not over ten 

 per cent of clay. Such soils are harsh to the feel, lack 

 cohesion, permit the water that falls upon them to pass 

 instantly through them, and, as they heat up quickly, the 

 crops raised in them soon suffer from drought. In them 

 vegetation is early, but less vigorous and sustained. They 

 do not readily combine with manures, the soluble parts of 

 which are leached into the subsoil, or are washed out by 

 the rains ; so that, if manure be not constantly applied, 

 they will yield but a moderate crop. Gravels are, in this 

 respect, from the coarseness of their particles, still worse 

 than sands, and are very properly called " hungry soils." 

 Indeed, the fertility of a soil depends in a very great de- 

 gree upon the fineness of its particles. Sand is sparingly 



