1762 



The Cornell Reading-Courses 



One may see these results wherever he is, and may observe the processes 

 that have given rise to them. They may differ in magnitude, but not in 

 kind. Note how frost breaks up clods of clay and even of stone; how 

 the rivulets after a rain gully the hillside and leave a mass of gravel or 

 mud where the water comes to rest. Then note the plants that spring up, 

 and observe their roots — how they thread their way about through the 



spaces in rock and soil, 

 expanding each a little 

 by their growth and 

 tlu'ir search for water 

 and food. 











:.o 



Fig. 6. — Diagram representing a characteristic section of 

 glacial till soil, and showing the lack of sorting and 

 stratification. Coarse and fine material are mixed 

 together promiscuously 



Scheme of classification 



The differences in 

 the physical and 

 chemical properties of 

 soil which determine 

 its crop relations and 

 its tillage properties 

 are due to (i) the 

 method by which the 

 soil was formed, (2) the 

 kind of material from 

 which it was formed, 

 and (3) the condition 

 under which it has 

 of all natural objects, 

 These in 



existed since it was laid down. As in the case 



soils are classified according to a regular system of factors. 



the order in which they are applied, beginning with those of widest area 



of influence, are : 



I. Mode of formation 



Under this head come the various processes by which rocks and other 

 soil materials are broken down to form soils, and by which they are carried, 

 sorted, and deposited. They are: 



(a) The natural weathering or decay of rocks to form residual soils. — The 

 decay of many feet of limestone may form only a few feet of soil. Shale 

 rock may be changed to soil with very little loss. In New York residual 

 soils are of limited extent and are found south of the Allegheny river in 

 southwestern New York where they form rough land derived from shale 

 and sandstone rock. 



