CAPILLARY ACTION 105 



tubes, and the height finally reached, while the soluble 

 organic matters present in soils have a contrary effect. The 

 results at present obtained are not, however, sufficiently 

 definite to justify any practical conclusions on the subject. 



The practical effect of capillary action in raising water to 

 the surface of the soil, or to the level occupied by plant 

 roots, has apparently been a good deal exaggerated ; its. 

 influence on the distribution of water in the soil is never- 

 theless very large. We must recollect that capillary action 

 is by no means confined to the raising of water, its effects 

 are indeed most limited in this direction as it is then opposed 

 by the force of gravity. The greatest manifestation of 

 capillary action is seen in the distribution of water in a dry 

 soil after a shower of rain. It is the surface attraction of 

 the particles of the soil for water which causes the rain 

 to be sucked down, with the energy with which we all are 

 familiar, and carried into the finest passages and remotest 

 portions of the soil. 



When the percolation produced by the attraction of gravity 

 has ceased, the system of soil and water is in a condition of 

 equilibrium, the nature of which in the case of sandy soils is 

 well shown by the upper half of Table XI. If water is now 

 removed from any portion of this system by root-action, or by 

 evaporation at the surface, the equilibrium is upset, and the 

 water coating the particles is induced by the local alterations in 

 its tension to redistribute itself, and regain once more the state 

 of equilibrium. In the case of coarse sands, this redistribution 

 consists mainly in the movement of the film of water coating 

 the particles, and such movement will be extremely slow; it will 

 however persist at a diminishing rate till the amount of water 

 in the soil is reduced nearly to the proportion of so-called 



