CHAPTER III 



KELATIONS OP SOIL TO WATER (continued) 



Capillary Action Evaporation from Bare Soil Influence of Crop on Evap- 

 oration Underground Water Wet and Dry Soils Amelioration of the 

 Physical Properties of Soil. 



Capillary Action. The rapid movements of water and other 

 liquids in porous bodies is a fact with which all are familiar ; 

 the rise of water in a lump of sugar, the spreading of a drop 

 of water in blotting paper, the rise of oil in a wick, are all 

 examples of capillary action. The typical instance, which 

 supplies the name for the whole of the phenomena, is supplied 

 by the rise of liquids in narrow tubes. The height to which 

 water will rise in glass tubes of various diameters is as 

 follows : 



Height to which Water at o C. rises in glass tubes 



Tube 1 mm. diameter, water rises to 15-336 mm. 

 0-1 153-36 



it 0-01 1533.6 



The height is thus greater the narrower is the tube. A 

 reduction of the diameter to one-tenth causes the water 

 to rise to ten times the previous height. The height to 

 which a liquid rises is somewhat diminished by an increase 

 in temperature. 



The rise of a liquid in a narrow tube or passage is only 

 a particular manifestation of the familiar adhesion between 

 a solid and liquid which is seen when a stick or clean stone 



