Glaciers--their Nature and Composition--their unceasing Motion --Powerful Agents of Denudation--Icebergs--their Number and Size--Erratic Blocks and loose Gravel spread out over Mountains, Plains, and Valleys, at the Bottom of the Sea --Characteristic Marks of moving Ice--Evidence of ancient Glacial Action--Illustrations from the Alps--from the Mountains of the Jura--Theory applied to Northern Europe--to Scotland, Wales, and Ireland--The Fact of Denudation established--Summary of the Evidence--This Fact the first Step in Geological Theory, 71 CHAPTER V. STRATIFIED ROCKS OF MECHANICAL ORIGIN--THEORY DEVELOPED AND ILLUSTRATED. Formation of Stratified Rocks ascribed to the Agency of Natural Causes--This Theory supported by Facts--The Argument stated--Examples of Mechanical Rocks--Materials of which they are composed--Origin and History of these Materials traced out--Process of Deposition--Process of Consolidation --Instances of Consolidation by Pressure--Consolidation perfected by Natural Cements--Curious Illustrations--Consolidation of Sandstone in Cornwall--Arrangement of Strata explained by intermittent Action of the Agents of Denudation, 87 CHAPTER VI. STRATIFIED ROCKS OF MECHANICAL ORIGIN--FURTHER ILLUSTRATIONS. Impossible to witness the Formation of Stratified Rocks in the Depths of the Ocean--On a small scale Examples are exhibited by Rivers and Lakes--Alluvial Plains--their extraordinary Fertility --Great Basin of the Nile--Experiments of the Royal Society--The Mississippi and the Orinoco--Some Rivers fill up their own Channels--Case of the River Po--Artificial Embankments--Large Tract of Alluvial Soil deposited by the Rhone in the Lake of Geneva--Deltas--The Delta of the Ganges and Brahmapootra--Delta of the Nile, 100 CHAPTER VII. STRATIFIED ROCKS OF CHEMICAL ORIGIN. Chemical Agency employed in the Formation of Mechanical Rocks--But some Rocks produced almost exclusively by the Action of Chemical Laws--Difference between a Mixture and a Solution--a Saturated Solution--Stalactites and Stalagmites--Fantastic Columns in Limestone Caverns--The Grotto of Antiparos in the Grecian Archipelago--Wyer’s Cave in the Blue Mountains of America--Travertine Rock in Italy--Growth of Limestone in the Solfatara Lake near Tivoli--Incrustations of the Anio --Formation of Travertine at the Baths of San Filippo and San Vignone, 109 CHAPTER VIII. STRATIFIED ROCKS OF ORGANIC ORIGIN--ILLUSTRATIONS FROM ANIMAL LIFE.