CHAPTER XII.. Surface, Hydrostatic and Ground Water. Percolation,

SURFACE, HYDROSTATIC AND GROUND WATER. PERCOLATION, 215.—Amount of Rainfall, 215.—Natural Disposition of Rain Water, 216.—The Surface Runoff, 216.—Washing-away and Gullying in the Cotton States, 217.—Injury in the Arid Regions, 219.—Deforestation, 219.—Prevention of Injury to Cultivated Lands from Excessive Runoff, 220.— Absorption and Movements of Water in Soils, 221.—Determination of Rate of Percolation. Diagram, 221.—Summary, 224.—Influence of Variety of Grain-sizes, 224.—Table of King’s Experiments, 224.—Percolation in Natural Soils. Figure, 225.—Ground or Bottom Water, 227.—Lysimeters, Surface of Ground Water; Variations, 227.—Depth of Ground Water most Favorable to Crops, 228.—Moisture Supplied by Tap Roots, 229.—Reserve of Capillary Water, 229.—Injurious Rise of Bottom Water from Irrigation, 230.—Consequences of the Swamping of Irrigated Lands; Prevention, 231.—Permanent Injury to certain Lands, 231.—Reduction of Sulfates, 232.—Ferruginous or Red Lands, 233.