In this case water had undoubtedly passed by capillary movement from the depth of eight feet to a point near the surface where direct evaporation could occur. As explained in the last chapter, water which is held as a film around the soil particles is called capillary water; and it is in the capillary form that water may be stored in dry-farm soils. Moreover, it is the capillary soil-moisture alone which is of real value in crop production. This capillary water tends to distribute itself uniformly throughout the soil, in accordance with the prevailing conditions and forces. If no water is removed from the soil, in course of time the distribution of the soil-water will be such that the thickness of the film at any point in the soil mass is a direct resultant of the various forces acting at that particular point. There will then be no appreciable movement of the soil-moisture. Such a condition is approximated in late winter or early spring before planting begins. During the greater part of the year, however, no such quiescent state can occur, for there are numerous disturbing elements that normally are active, among which the three most effective are (l) the addition of water to the soil by rains; (2) the evaporation of water from the topsoil, due to the more active meteorological factors during spring, summer, and fall; and (3) the abstraction of water from the soil by plant roots. Water, entering the soil, moves downward under the influence of gravity as gravitational water, until under the attractive influence of the soil it has been converted into capillary water and adheres to the soil particles as a film. If the soil were dry, and the film therefore thin, the rain water would move downward only a short distance as gravitational water; if the soil were wet, and the film therefore thick, the water would move down to a greater distance before being exhausted. If, as is often the case in humid districts, the soil is saturated, that is, the film is as thick as the particles can hold, the water would pass right through the soil and connect with the standing water below. This, of course, is seldom the case in dry-farm districts. In any soil, excepting one already saturated, the addition of water will produce a thickening of the soil-water film to the full descent of the water. This immediately destroys the conditions of equilibrium formerly existing, for the moisture is not now uniformly distributed. Consequently a process of redistribution begins which continues until the nearest approach to equilibrium is restored. In this process water will pass in every direction from the wet portion of the soil to the drier; it does not necessarily mean that water will actually pass from the wet portion to the drier portion; usually, at the driest point a little water is drawn from the adjoining point, which in turn draws from the next, and that from the next, until the redistribution is complete. The