CHAPTER XV. COLORS OF SOILS, 283.—Black Soils, 283.—“Red” Soils, 284.—Origin of Red Tints, 285.—White Soils, 285.—Differences in Arid and Humid Regions, 286.—White Alkali Spots, 286. CHAPTER XVI. CLIMATE, 287.—Heat and Moisture Control Climates, 287.—Climatic Conditions, 287.—_Ascertainment and Presentation of Temperature Conditions_, 288.—Annual Mean not a Good Criterion, 289.—Extremes of Temperature are most Important, 289.—Seasonal and Monthly Means, 289.—Daily Variations, 290.—_The Rainfall_, 290.—Annual Rainfall not a Good Criterion, 290.—Distribution most Important, 290.—_Winds_, 291.—Heat the Cause of Winds, 291.—Trade Winds, 291.—Cyclones, 292.— Influence of the Topography on Winds; Rains to Windward of Mountains, Arid Climates to Leeward, 293.—General Distribution of Rainfall on the Globe. Figure, 294.—Ocean Currents, 295.—The Gulf Stream, 295.—The Japan Stream, 296.—Contrast of Climates of N. W. America, 297.—Continental, Coast and Insular Climates, 297.—Subtropic. Arid Belts, 298.—Utilization of the Arid Belts, 299. CHAPTER XVII. RELATIONS OF SOILS AND PLANT GROWTH TO HEAT, 301.—Temperature of Soils, 301.—Water Exerts Controlling Influence, 301.—Cold and Warm Rains, 302.—Solar Radiation, 302.—Penetration of the Sun’s Heat into the Soil, 302.—Change of Temperature with Depth, 303.—Surface Conditions that Influence Soil Temperature, 303.—Heat of High and Low Intensity, 304.—Reflection vs. Dispersion of Heat, 304.—Influence of Vegetation, and of Mulches, 305.—Influence of the Nature of the Soil-Material, 306.—Influence of Evaporation, 307.—Formation of Dew, 307.—Dew rarely adds Moisture, 308.—Dew within the Soil, 308.—Plant Development under Different Temperature-Conditions, 309.—Germination of Seeds; Optimum Temperature for each Kind, 309.—Artificial Heating of Soils; by Steam Pipes or Water, 310.