90 



ELEMENTS OF AGRICULTURE 





ifJSJP 



Fig. 12, and the total amount of film moisture that the 

 marbles would carry is represented in the tube placed 

 beside the tumbler. The soil in the other 

 tumbler (Fig. 13) is of the same weight as 

 the marbles in Fig. 12, and it represents the 

 marbles reduced to the fineness of common 

 sand. Its capacity for holding film moisture 

 is represented by the water in the standing 

 tube (Fig. IS). The weight of material is 

 the same in each tumbler, and the reason 

 why one holds three times more film moist- 

 ure than the other is due to the increase of 

 surface that comes by dividing a coarse lump 

 into fine particles."* 



This experiment seems to prove conclu- 

 sively that the power of a soil to hold water 

 depends in a large measure upon the fine- 

 ness of its particles. 

 92. Free Water. — 



When rain falls on the 



surface of the earth, 



part of it sinks into 



the soil until it reaches 



some hard layer of 



earth or rock, through 



Fig. 



Fig. 13.— Film 

 - -a— moisture held by 



T^Til S b fA a b Z * hich " CaMOt P aSS - rc r e b d M to Wh pSwder: 



g"o 1 ^ I . n ii' H &p2t The water that has ^rSeTtt 



ment Station.) -, • i j £ ment Station.) 



water 

 drained down from 

 the soil above rests on this layer, and follows it until it 

 comes out as a spring or well. Fig. 14 shows how 



♦Cornell Experiment Station Bulletin, No. 174. 



