THEORY OF DENUDATION--CONCLUDED.
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