EXERCISE 70 A 

 WHAT IS THE WATER-RETAILING CAPACITY OF DIFFERENT: #.$03$, OF ^S 



Materials. Glass tubes used in Exercise 69 ; cork stoppers. > >V > 'A 



Directions. Fasten a glass tube in a vertical position. Close the bottom with a stopper which 

 has had a notch cut on one side to allow water to leak out. Put a piece of blotting paper in the 

 bottom of the tube on the stopper, if necessary, to hinder the soil from falling through the hole. 



Fill the tube two thirds full of dry soil, the weight of which has been ascertained. Press the 

 soil down lightly. Pour in measured quantities of water (distilled water if possible) from time to 

 time, until the soil is soaked to the bottom. Catch the water, if any, that niters through. When 

 the water has ceased to come through, measure it and compare with the amount poured into the 

 tube. Calculate the amount of water retained per gram of soil. 



Several different types of soil should be used by different members of the class and final results 

 compared. If soils containing much clay are used, the water will pass through very slowly. 



Additional problems. Do different kinds of soil have different capacity for water ? 

 What relation is there between capacity for water and drainage of soils ? 



L 101 J 



