EXERCISE 18 (Continued) 



(49) 



4. After placing the tubes in the support block (Fig. 14) connect the tubes 



at the top with rul)ber tubing and place beaker glasses underneath them 

 to catch the water which comes through. 



5. Record the time elapsing after water is turned on until it begins to perco- 



late through each tube of soil. 



6. Determine the quantity of water draining through each soil in thirty 



minutes after it begins. 

 Note. — This exercise could be tried with five soils as suggested in Fig. 15. 



QUESTIONS 



Upon what two main factors does percolation depend? 



Would water percolate faster through soil which was dry at first or through 



wet soil? Why? 

 What conditions in the soil assist percolation? 



4. Is a sandy soil objectionable when percolation is considered? 



5. What does this experiment indicate concerning the depth of plowing? 



6. Would growing crops be benefited by a loose condition of the surface 



soil? 



7. Would there be any advantage in fall plowing? Why? 



8. Why are clay soils often wet? 



9. What does this experiment indicate concerning the comparative depth 



at which tile drains should be put in a clay soil and in a sandj' soil? 



