A UNIT IN AGRICULTURE 39 



cold soil? By a dry soil? By a wet soil? Review Exercise 14 and 

 state whether there is any relation hetween soil temperature and air 

 space. What are some of the ways in which a cold soil may be made 

 warmer ? 



Ex. 19. Water Capacity of Soils. 



Material : different kinds of soils, five long-necked bottles with 

 the bottoms broken off, rack for holding bottles, five tumblers. Tie a 

 small piece of cheese cloth over the mouth of each bottle, place in the 

 frame upside down with a tumbler under each. Fill the bottles to 

 the same height, about two-thirds full, with different kinds of soil. 

 Firm the soils by shaking the bottle. With watch in hand and glass 

 of water held as ne?r as possible to the soil, pour water into one of 

 the bottles just fast enough to keep the surface of the soil covered. 

 Note how long before the water begins dropping into the tumbler 

 below. Do the same with each of the other bottles. Which takes in 

 water most rapidly ? Which most slowly ? Which is the most porous ? 

 Which is the least porous? Compare results with results in Exercise 

 18. What happens to the less porous soils when a heavy shower of 

 rain comes? Repeat the experiment with any two of the soils, pack- 

 ing the soil in the bottle tightly before pouring in the water. What 

 is the effect of packing? Does this experiment have any bearing on 

 farm practice ? What bearing has it ? Which of the soils could absorb 

 the heaviest shower? Which soil continued to drip longest? Which 

 would drain most readily? 



Ex. 20. Capillarity of Soils. 



Material : same as in Exercise 19. Fill each bottle with a differ- 

 ent kind of dry soil. Fill each tumbler about two-thirds full of water 

 and set the bottles, neck down, in the tumblers so that the cheese 

 cloth is just above the bottom of the tumbler. Observe the rise of 

 water in the different soils. Note how high it rises in each bottle and 

 the time it takes. In which soil does the water rise most rapidly? 

 In which to the greatest height? Which soil draws up the greatest 

 amount of water ? This can be determined by measuring or weighing 



