CLASSIFICATION AND PROl'KRTI F.S OF SOIL. 



51 



(/) Allow the liquid todiip foi- half ;m hour, and com- 

 pare the water which now percolates ihrounii with tiiat 

 first percolated. Is it safe to depend upon the soil to act 

 as a filter in purifyint^ the water of wells from org-anic 

 matter ? 



(y) Very carefully pour off all tlie water remaining- in 

 the tubes, and weigh each tube with its contents, record 

 the weights, and compare with those of (e). Which soil 

 retained the greatest amount of water ? 



Experiment 6. — (a) Procure a set of capillary tubes 

 (Fig. 17) — four or five tubes — varying in diameter from 

 a hair tube to one one-fourth inch in diameter. 



{/>) Half fill a beaker, f)r tuml)ler, 

 with water colored with red ink. 



(r) In a piece cf pasteboard punch 

 several holes corresponding in size 

 and numl)er to the tubes used; thrust 

 the tubes through the holes to 

 three-fourths the distance, below, of 

 the height of the beaker Now cover 

 the beaker with this 'pasteboard, 

 allowino- the tubes to extend down 



*^- 



m 



:U'U- 



FIG. 17. — APPARATUS 

 FOR KXPEKIMENT 6. 



into the coloretl liquid (Fig. 17). 

 {d) Note the hc'.ght to which the 



Capillarj' rise of liquid not Hquid risCS iu Cacll tubc. In wllicll 

 shown. highest? 



The wall of the tube attracts the film of water 

 next to it, and tends to spread it out over the 

 surface of the tube, overcoming the resistance 

 of the surface tension of the liquid itself. Notice 

 that the surface of the liquid both inside and 

 outside of the tubes assumes a concave shape, 

 on account of the creeping up of the liquid next 

 to the wall, caused by the attraction between 



