Chapter 14

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

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