36 AGRICULTURE. 



little humus. More plants grow and more humus is formed, 

 until out of the material that came from the hard tough rocks 

 and the decay of roots and leaves a fine soil is formed, sandy 

 in one place, clayey in another, and loamy in another. 



CONCLUSIONS : 



1. All our soils have come from the breaking down of rocky 

 material and the decay of former plants. 



2. Soils may be classed as follows : Sandy, clay, loam, and 

 vegetable or humus soils. 



3. The texture of the soil depends upon the amount of sand, 

 clay, and humus mixed together forming it. 



4. The nature of the soil depends to a large extent upon the 

 nature of the rocks out of which the sand and the clay have 

 been formed. 



5. The rocks have oeen broken up by the action of the air, 

 the freezing of the rain-water in the rocks, the grinding of ice, 

 and the downrush of rains and streams. 



6. Some soils have been carried about from one place to 

 another, and spread out by ice, snow, streams, and even to 

 some extent by the wind. 



7. Some soils have been formed out of the rocks beneath 

 them, and from the decay of plants growing upon them. 



8. Some soils, such as swamp soils, have been formed almost 



entirely from the decay of plants. 

 SUGGESTIVE : 



\Yhatclassofplantsaremostusefulin improving the soil, those with 

 shallow growing roots or those having deep growing roots ? Have you 

 observed any difference between the roots of clover and of timothy ? 



