CAPILLARY MOVEMENT AND TEXTURE 



175 



led toward these small pores by their attraction for 

 water. 



Three primary soil factors govern the capillary 

 movement of water. These are: (a) Texture, (6) struc- 

 ture, (c) dampness of the soil. In addition to these, 

 the movement is affected by (d) the surface tension 

 of the soil water, and (e) by the condition of the surfaces 

 of the soil particles. 



65 r 



60 



45 



2 40 



I 



o 



35 



z 



u 30 



CO 



s 



u.25 

 o 



h 



20 



15 



10 



c 



14 



16 



18 



ao 



8 10 12 



TIME IN HOURS 



Fig. 54. Curves showing the height and rate of rise of water in dry soils 

 of different texture as given in Table XXIX. 



84. Texture. The influence of texture was explained 

 in the principles outlined above. The finer the soil, 

 the more surface it will expose, the more points of con- 

 tact there will be between the particles, and therefore 

 the greater total curvature the water surfaces will have. 

 For this reason, a clay containing 20 per cent may draw 

 water from a sand containing 10 per cent of water. 



The capillary capacity of a soil may be measured 

 in two ways: (1) By the height to which water will 



