SOIL OF MANY KINDS 9 



into a firm, stony sphere, and made more complicated because of 

 the eternal forces which wrought such tremendous changes since 

 the earth began which forces brought into existence continents 

 and oceans, lakes and rivers, mountains, hills and valleys, deserts 

 and prairies. 



Weathering Continues Indefinitely. Weatheringdoes not cease 

 when it has reduced rocks to soil, but continues to act indefinitely 

 upon the soil itself. If it were not so the best prairie soils would be 

 incapable of supporting a single blade of grass. In this sense crops, 

 vegetation and life are possible upon this earth largely because 

 of decay. 



Soil from Rock May be Observed. Soil wherever found is 

 underlaid by some kind of rock it may be the rock from which the 

 soil was formed or some foreign rock. Where soil is found Under- 

 laid by its parent rock there is no definite dividing line between the 

 solid rock and the soil above it the one grades into the other. The 

 lower stratum of the soil has a composition approaching that of 

 crumbled and decayed rock. Lower down the rock characteristics 

 appear more plainly, and still farther down occurs the solid 

 rock itself. 



Soils are Carried Away after They Form. All the soil we see 

 was not formed from the rock that may be found under it. This is 

 due to the fact that many soils are carried away after they are 

 formed and deposited on other rocks. Water, ice and wind are and 

 have always been the main soil transporting agents. 



Soil of Many Kinds. Because of the source of soil building 

 materials, the nature of soil formation, the forces to which the earth 

 has been and is being subjected, and because of the transporting 

 and mixing action of water, wind and ice, all soil can not be the 

 same, but must necessarily varyin composition, both physically and 

 chemically. These variations give rise to. many kinds and types 

 of soil, and necessitate convenient classification. A knowledge of 

 these soil variations, classes and types becomes of primary 

 importance. 



Illustration Material for Lessons. Students should bring to class: 



1. Specimens of rocks undergoing weathering. 



2. Samples showing gradations of rock into soil. 



Field Studies. 1. Observe if possible the weathering of native rock into 

 soil, and note the action of the various weathering agents. 



2. Observe the transportation and movement of soil. 



3. Observe various kinds of soil note location, etc. 



