100 



ELEMENTARY SCIENCE 



portions of sand and clay, but the following rough classi- 

 fication may be made: 



Summary : Soils may be classified as follows: 



As to origin. Residual soil. 



Transported soil. 



Alluvial soil. 



Eolian soil. 



Glacial soil. 



As to nature. Chemically, on the basis of chemical 



analyses of its constituents, or 

 Physically, on the basis of the size and 

 texture of its grains (see table above). 



QUESTIONS 



1. What are the different kinds of soils? 



2. Why do we "rotate" crops? 



3. Why does the fertility of residual soils vary more than the fer- 



tility of transported soils? 



4. In what respects are the following residual soils good, and in 



what respects are they bad: sandy soil, day soil, limestone 

 soil? 



5. What are alluvial soils? Are they good or bad ? 



6. What are eolian soils? 



7. What are the various things that transport soil? 



8. What are fertilizers? How do we learn what fertilizers to use? 



9. What is the best kind of soil, and why? 



