EXERCISE 7 (Continued) (27) 



3. Give a definition of true specific gravity. 



4. Of what value to the farmer is a knowledge of the specific gravity of his 



soil? Would it indicate anything regarding the amount of humus or 

 the amount of sand? 



5. Name the four principal minerals from which soil has been derived. State 



and discuss their specific gravities. 



6. Wliat is the average specific gravity of soil grains? 



7. Look up the specific gravities of sand, silt, and clay iind discuss them. 



