114 



EXPi':uiMi':xTs with plants 



3. Apparatus for 

 measuring the 

 rate of evapo- 

 ration from a 

 satui-ated soil. 



has the larg'er pai'tiek'.s; the hirger spaces; does this 



explain the matter! An inch of rain is said to pene- 

 trate four inches in clayey soil and six to 

 eight inches in sandy soil. What do you 

 think of this statement ? Does air in the 

 soil hinder percolation ? 



What becomes of the rain-water which 

 percolates down through the soil ; is any of 

 it drawn back up again as the surface dries? 

 Prepare a bent tube as shown in Fig. ^Q^ 

 one arm being about eighteen inches long 

 and the other about four inches. Push a 

 little wet cotton nearly to 



the bottom of the longer arm; fill 



this with clay; fill the longer arm of 



a similar tube with sand. Attach a 



funnel, as shown in Fig. 87, and pom- 

 water upon the soil in each tube until 



the shorter arm of the tube is partly 



filled; when it stops rising, remove 



the funnel and pour a few drops of 



oil on the surface of the water in the 



shorter arm of the tube, to prevent 



evaporation. Mark accurately on a 



strip of paper gummed to the tube 



the height of the water -column (it 



should be about the same in botli 8?. Method of supplying 



. , . Ti> j^i j^ n ^^ ' 2.^ water to the apparatus 



tubes). It the water tails m the shown in Fig. so. 



