CHAPTER I.

AGENCIES OF SOIL FORMATION, 1.—1. _Physical Agencies_, 1.—Effects of Heat and Cold on Rocks, 1.—Unequal Expansion of Crystals, 2.—Cleavage of Rocks, 3.—Effects of Freezing Water, 3.—Glaciers; Figure, 3.—Glacier Flour and Mud, 4.—“Green” and “White” Rivers, 4.—Moraines, 5.—Action of Flowing Water, 5.—Enormous Result of Corrasion and Denudation, 6.—Effects of Winds, 8.—Dunes, 8.—Sand and Dust Storms in Deserts, Continental Plateaus and Plains, 8.—Loess of China, 9.—Migration of Gobi Lakes, 9.—_Classification of Soils_, 10.—Their Physical Constituents, 10.—Sedentary or Residual Soils, 11.—Colluvial Soils, 12.—Alluvial Soils. Diagram, 12.—Character of these Soil Classes, 13.—Richness of Flood-plain and Delta Lands, 14.—Lowering of the Land Surface by Soil Formation, 15.