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.
Soils, Their Formation, Properties, Composition, and Relations to Climate and Plant Growth in the Humid and Arid Regions · The Wunder Library — complete classics, free to read, with narration.