_Pages_ 72-82 CHAPTER VI GEOGRAPHICAL AND GEOLOGICAL CHANGES: THE PERMANENCE OF CONTINENTS Changes of Land and Sea, their Nature and Extent--Shore-Deposits and Stratified Rocks--The Movements of Continents--Supposed Oceanic {xiii} Formations; the Origin of Chalk--Fresh-water and Shore-deposits as Proving the Permanence of Continents--Oceanic Islands as Indications of the Permanence of Continents and Oceans--General Stability of Continents with Constant Change of Form--Effect of Continental Changes on the Distribution of Animals--Changed Distribution Proved by the Extinct Animals of Different Epochs--Summary of Evidence for the General Permanence of Continents and Oceans. _Pages_ 83-105 CHAPTER VII CHANGES OF CLIMATE WHICH HAVE INFLUENCED THE DISPERSAL OF ORGANISMS: THE GLACIAL EPOCH Proofs of the Recent Occurrence of a Glacial Epoch--Moraines--Travelled Blocks--Glacial Deposits of Scotland: the "Till"--Inferences from the Glacial Phenomena of Scotland--Glacial Phenomena of North America--Effects of the Glacial Epoch on Animal Life--Warm and Cold Periods--Palaeontological Evidence of Alternate Cold and Warm Periods--Evidence of Interglacial Warm Periods on the Continent and in North America--Migrations and Extinctions of Organisms Caused by the Glacial Epoch _Pages_ 106-124 CHAPTER VIII THE CAUSES OF GLACIAL EPOCHS Various Suggested Causes--Astronomical Causes of Changes of Climate--Difference of Temperature Caused by Varying Distances of the Sun--Properties of Air and Water, Snow and Ice, in Relation to Climate--Effects of Snow on Climate--High Land and Great Moisture Essential to the Initiation of a Glacial Epoch--Perpetual Snow nowhere Exists on Lowlands--Conditions Determining the Presence or Absence of Perpetual Snow--Efficiency of Astronomical causes in Producing Glaciation--Action of Meteorological Causes in Intensifying Glaciation--Summary of Causes of Glaciation--Effect of Clouds and Fog in Cutting off the Sun's Heat--South Temperate America as Illustrating the Influence of Astronomical Causes on Climate--Geographical Changes how far a Cause of Glaciation--Land Acting as a Barrier to Ocean-currents--The Theory of Interglacial Periods and their Probable Character--Probable Effect of Winter in _aphelion_ on the Climate of Britain--The Essential Principle of Climatal Change Restated--Probable Date of the Last Glacial Epoch--Changes of the Sea-level Dependent on Glaciation--The Planet Mars as Bearing on the Theory of Excentricity as a Cause of Glacial Epochs _Pages_ 125-168 {xiv} CHAPTER IX ANCIENT GLACIAL EPOCHS, AND MILD CLIMATES IN THE ARCTIC REGIONS