Primer of Irrigation

worth encouraging. In what are known as "dry" climates there is always some moisture in the atmosphere which is deposited upon the soil, for wherever there are oxygen and hydrogen there must be moisture. But the quantities vary in climates as much as they do in soils. Where there is evaporation from the soil moisture during the day there is also a re-absorption of moisture by the soil at night and, with this fact in mind, it may be laid down as an axiom: The tendency of water is to evaporate from the soil into the atmosphere during the day and to fall back upon the soil during the night. To reduce the idea to an axiom: A dry soil has an affinity for a moist atmosphere, and a dry atmosphere loves a moist soil. SATURATION AND POWER TO RETAIN MOISTURE. The rain falls and is drunk in by the thirsty soil; the dew descends and is absorbed, and the waters of irrigation poured upon the ground quickly disappear. But after much water falls upon the earth the latter becomes saturated, can hold no more, and the surplus runs off the surface or sinks down through until it reaches the water table. This happens more speedily in some soils than in others. Thus, 100 pounds of dry soils, as here specified, will hold the quantity of water set opposite their respective names without dripping or running off. Quartz sand 25 pounds Calcareous sand 29 pounds Loamy soil 40 pounds Clay loam 50 pounds Pure clay 70 pounds But dry, peaty soils and adobe will absorb a much...