100 



FIRST TEAR SCIENCE 



agricultural plants are to be provided with sufficient 

 moisture. 



Experiment 66. Fill full of soil four tin cans having small holes 

 punched in the sides and bottom. Water each with the same amount 

 of water. Cover the first with about an inch of g'rass and the second 

 with about an inch of sawdust, and weigh carefully. Weigh the third 

 and fourth. Record the weight of each. Thoroughly stir the sur- 

 face of the third, as soon as it is dry enough, about an inch deep. 

 Keep this stirred. Let the fourth stand undisturbed. Weigh all four 

 every school day for two weeks. Keep a record of the loss of weight 

 of each. Why have they lost weight ? How do the grass, the saw- 

 dust, and stirring of the earth affect the loss ? Suggest ways to keep 

 soils from losing their moisture. 



In Experiment 56, it was seen that if a layer of grass 

 or sawdust was put on the top of the soil, the moisture did 



"DRY FARMING" IN EGYPT. 



not evaporate as rapidly as it did when the soil Was not 

 covered. The grass could have been replaced by shav- 

 ings, manure, or any substance which would protect the 



