CAPILLARY WATER 



103 



water. Nine tenths of the weight of some common plants 

 is water. In a very dry season, or in a dry place, too 

 much of this essential water evaporates from the body of 

 a plant, and the plant wilts. This is because the water 

 was needed to fill out its body, and to give it substance 

 and stiffness. 



Water exists in the soil both as free water and as film 

 water. If a tin can is filled with 

 pebbles and water, and if then a 

 small hole is made in the bottom of 

 the can, the free water will run out, 

 and leave the film water coating 

 the pebbles. So while the free wa- 

 ter can be drained off the land, the 

 film water cannot be. 



62. Capillary Water. Film water 

 is often called capillary water. The 

 word "capillary" means hair-like, 

 and it refers to the hair-like, irregu- 

 lar spaces between the small soil 

 particles. It is in these spaces that 

 film water, or capillary water, is 

 found. By placing the corner of a 

 blotter in a little water, one can see 

 how capillary water behaves. The 

 water rises through the blotter 

 rapidly at first, and then more 



slowly. The rise is due to the attraction which the paper 

 fibers have for the water films. This is known as film 

 attraction, or capillary attraction. In the soil, capillary 

 attraction tends to transfer water from its moist parts to its 

 dry parts. This transfer may be in any direction, up, 

 down, or sidewise. 



The amount of capillary water which a soil can hold 



CAPILLARY ATTRACTION. 



The height of the water 

 in the tubes varies in- 

 versely with the size of 

 the bore. 



