210 SOILS. 



upon which no rain had since fallen, showed in July in the 

 second foot, upon which rested ten inches of fully air-dried soil 

 free from vegetation, a water-percentage of eight per cent. 1 



Capillary Action in Moist Soils. In the preceding discus- 

 sion the case of columns of air-dry soils, so common in the 

 arid regions, has been considered. It is obvious that a soil 

 column holding the minimum of capillary water may be of 

 any height; so that when, as happens in the open field, the 

 rain water soaks down beyond the range of capillary rise in a 

 given soil, the upper portions of the latter, above that range, 

 will remain at the minimum of moisture-content so long as it 

 is not depleted by evaporation. King has made extended 

 observations on soil columns ten feet high and moistened 

 throughout the mass. Capillary movement takes place in 

 moist soils much more rapidly than in dry ones, although 

 when sufficient time is given the final adjustment will of 

 course be the same. King's experiments showed that evapor- 

 ation at the surface of the tenfoot columns caused a sensible 

 depletion of the water content originally existing at the depth 

 of ten feet, in the course of 314 days. While so slow a 

 movement might not be of any benefit during the growth- 

 period of shallow-rooted annual crops, the fact shown is of 

 importance to permanent plantings, as of trees and vines. 



Another and not so readily intelligible effect observed by 

 King is that when the surface-soil is wetted, moisture may be 

 withdrawn toward the surface from the lower layers. In one 

 experiment he found that when water was applied on the sur- 

 face so as to add two pounds of water to each surface foot in 

 several soils, at the end of 26 hours there had been an increase 

 of three pounds in the same, and a loss of one and three quarter 

 pounds from the second and third feet. The cause of this 

 translocation is probably a " distillation " of the subsoil mois- 

 ture toward the cooled soil ; the fact that it occurs is of prac- 

 tical interest, since it seems to show that wetting the upper 



1 Hall (The Soil, p. 66) gives for the minima in the case of soils examined by 

 him the following figures : coarse sandy soil, 22.2, light loam, 35.4, stiff clay, 45.6, 

 sandy peat, 52.8. These figures are very much higher than for apparently similar 

 materials used by the writer, and the differences exceed those between the 

 maxima given for the same. This discrepancy I am unable to account for. 



