22 ELEMENTS OE AGRICULTURE 



river bottoms usually richer than the soil of hillsides ? 7. When 

 you stir up soil in water, which particles settle first after you 

 stop stirring? 8. Why does not the water become perfectly 

 clear at once? 9. Where does the sea get its salt? 10. How 

 are salts carried from the land to the sea? 11. Does rain water 

 contain any salt? 12. What is a hard water? 13. What is a 

 soft water? 



PROBLEM 



An acre of soil one foot deep contains 43,560 cubic feet. The 

 Mississippi River carries annually to the ocean about 3,702,- 

 758,400 cubic feet of solid material. How many acres of soil 

 one foot deep would this amount of material form? 



