192 A YEAR IN SCIENCE 



Based upon the proportions of sand and clay in soils, 

 Dryer gives the following classification : 



.Sandy soil 80% sand 10% clay 



Sandy loam 60-70% " 10-25% '' 



Loam 40-60% " 15-30% " 



Clay loam 10-35% " 30-50% ' 



Clay 10% " 60-90% " 



Questions 



1. What is soil? Sub-soil? 



2. What is the origin of all soil? 



3. What is residuary soil? 



4. What is drift soil? 



5. What are the chief agents in the production of 

 soil ? Explain fully the -work of each. 



6. How do clay and sand differ? 



7. Does either alone make a satisfactory soil for 

 plants? Give reason for your answer. 



8. What then is a good combination? 



9. Give Dryer's classification of soils. 



