CHAPTER XIII. WATER OF SOILS; THE REGULATION AND CONSERVATION OF SOIL, MOISTURE; IRRIGATION, 234.—Loosening of the Surface, 234.—Effects of Underdrains; Rain on Clay Soils, 235.—Winter Irrigation, 236.—_Methods of Irrigation_, 236.—Surface Sprinkling, 237.—Flooding, 237.—Check Flooding. Furrow Irrigation, 237, 238.—Figure Showing Penetration, 239.—Figure Showing Faulty Irrigation in Sandy Lands, 239.—Distance between Furrows and Ditches, 241.—Irrigation by Lateral Seepage, 242.—Basin Irrigation of Trees and Vines; Advantages and Objections, 243.—Irrigation from Underground Pipes, 245.—_Quality of Irrigation Waters_, 246.—Saline Waters; Figures of Effects on Orange Trees, 246.—Limits of Salinity, 246.—Mode of Using Saline Irrigation Waters; Apparent Paradox, 249.—Use of Drainage Waters for Irrigation, 250.—“Black Alkali” Waters, 250.—Variations in the Salinity of Deep and Shallow Wells, 250.—Muddy Waters, 251.—_The Duty of Irrigation Waters_, 251.—Causes of Losses, 252.—Loss by Percolation. Figure, 252.—_Evaporation_, 253.—Tables Showing same at California Stations, 255.—Evaporation in Different Climates; Table, 255.—Evaporation from Reservoirs and Ditches, 257.—Prevention of Evaporation; Protective Surface Layer, 257.—Illustrations of Effects of Tillage; Table, 258.—Evaporation through Roots and Leaves, 262.—Weeds waste Moisture, 264.—Distribution of Moisture in Soils as Affected by Vegetation, 264.—Forests and Steppes, 265.—Eucalyptus for Drying Wet Lands, 265.—Mulching; Effects on Temperature and Moisture, 266. CHAPTER XIV. ABSORPTION BY SOILS OF SOLIDS FROM SOLUTIONS. ABSORPTION OF GASES, AIR OF SOILS, 267.—_Absorption of Solids_, 267.—Desalination, 267.—Decolorization, 267.—Complexity of Soil-Action, Physical and Chemical, 268.—“Purifying” Action of Soils on Gases and Liquids, 269.—Waste of Fertilizers, 269.—Variation of Absorptive Power, 270.—Generalities Regarding Chemical Action and Exchange, 270.—Drain Waters, 271.—Distinctions not Absolute, 272.—_Absorption or Condensation of Gases by the Soil_, 272.—Proof of Presence of Carbonic and Ammonia Gases in Soils, 273.—Absorption of Gases by Dry Soils. Figure, 274.—Composition of Gases Absorbed by Various Bodies from the Air. Table, 275.—Discussion of Table, 277.—_The Air of Soils_, 279.—Empty Space in Dry Soils, 279.—Functions of Air in Soils, 279.—Insufficient and Excessive Aeration, 280.—Composition of the Free Air of Soils, 280.—Carbonic Dioxid vs. Oxygen, 281.—Relation to Bacterial and Fungous Activity, 281.—Putrefactive Processes, 282.