evaporation 62 per cent, and many experiments since that day have confirmed this conclusion.  At the Utah Station, under arid conditions, it was found that shading a pot of soil, which otherwise was subjected to water-dissipating influences, saved 29 per cent of the loss due to evaporation from a pot which was not shaded.  This principle cannot be applied very greatly in practice, but it points to a somewhat thick planting, proportioned to the water held by the soil.  It also shows a possible benefit to be derived from the high header straw which is allowed to stand for several weeks in dry-farm sections where the harvest comes early and the fall plowing is done late, as in the mountain states.  The high header stubble shades the ground very thoroughly.  Thus the stubble may be made to conserve the soil-moisture in dry-farm sections, where grain is harvested by the “header” method.

A special case of shading is the mulching of land with straw or other barnyard litter, or with leaves, as in the forest.  Such mulching reduces evaporation, but only in part, because of its shading action, since it acts also as a loose top layer of soil matter breaking communication with the lower soil layers.

Whenever the soil is carefully stirred, as will be described, the value of shading as a means or checking evaporation disappears almost entirely.  It is only with soils which are tolerably moist at the surface that shading acts beneficially.

Alfalfa in cultivated rows.  This practice is employed to make possible the growth of alfalfa and other perennial crops on arid lands without irrigation.

The effect of tillage

Capillary soil-moisture moves from particle to particle until the surface is reached.  The closer the soil grains are packed together, the greater the number of points or contact, and the more easily will the movement of the soil-moisture proceed.  If by any means a layer of the soil is so loosened as to reduce the number of points of contact, the movement of the soil-moisture is correspondingly hindered.  The process is somewhat similar to the experience in large r airway stations.  Just before train time a great crowd of people is gathered outside or the gates ready to show their tickets.  If one gate is opened, a certain number of passengers can pass through each minute; if two are opened, nearly twice as many may be admitted in the same time; if more gates are opened, the passengers will be able to enter the train more rapidly.  The water in the lower layers of the soil is ready to move upward whenever a call is made upon it.  To reach the surface it must pass from soil grain to soil grain, and the larger the number of grains that touch, the more quickly and easily will the water reach the surface, for the points of contact of the soil particles may be likened to the gates of the railway station.  Now if, by a thorough stirring and loosening of the topsoil, the number of points of contact between the top and subsoil is