OEIGIN AND FORMATION OF SOILS. 2S 



originated, and deposited from water or ice. The former 

 are called " alluvial ; " these occur not only in valleys 

 and river-beds, but in inland places, where they have 

 been deposited in lakes or other bodies of water. Those 

 deposited from ice are called " drift soils ; " these have 

 been formed by the action of "glaciers,'' vast bodies of 

 ice moving like a river, which carry considerable quanti- 

 ties of earth as well as numerous rocks. 



The results of glacial action are found, not only in 

 valleys, but in high mountains, where rocks show, by 

 well-defined scratches, the wearing and grinding effect of 

 the moving ice. 



Drift soils are distinguished from all others by the 

 presence of rounded rocks or bowlders, and, though not 

 uniform either in composition or character, are usually 

 fertile, the fertility being due chiefly to the bringing 

 together, from numerous sources, of a variety of min- 

 eral substances. 



Classification of Soils. — The principal ingredients 

 of soils are sand, clay, carbonate of lime, and vegetable 

 or organic matter. They are, therefore, divided into four 

 natural classes; viz., sandy, clayey, limy, and peaty, ac- 

 cording to the greater proportion in each case of one 

 of these four ingredients. 



What is Sand? — Sand or silica is composed of the 

 mineral silicon united with the chemical element oxygen, 

 and does not serve directly as food for plants. A soil 

 consisting entirely of sand would be useless to the farmer, 

 for he could produce nothing from it in its natural con- 

 dition. It possesses distinct properties, however, which 

 render soils containing considerable sand light and open, 



