174 DISCUSSIONS IN CLIMATOLOGY. 



have taken a long course of ages to have lowered them 

 to the extent of bringing the glacial state to a close. 

 In this case there ought to be a succession of beds 

 indicating the long continuance of cold conditions. 

 Instead of this, however, we have a glacial bed 

 immediately preceded and succeeded by beds indicating 

 an almost tropical condition of climate. When we 

 take this circumstance into consideration, along with 

 the evidence adduced by Mr. J. S. Gardner as to the 

 alternations of warmer and colder conditions in the 

 south of England and other parts of Europe during 

 the Eocene period, the conviction is forced upon us 

 that a high state of eccentricity is the most rational 

 explanation of these curious phenomena. 



The greater elevation of the Alps would undoubtedly 

 intensify the glacial condition of things, but it would 

 not originate it. The elevated character of the Alps, 

 for example, was no doubt the reason why the plains 

 of Switzerland, during the last glacial epoch, were so 

 much more buried under ice than other parts of 

 Southern Europe ; but their elevation was not that 

 which brought about the glaciation, for those plains 

 were free from ice both before and after the glacial 

 epoch, though the Alps were no doubt as high as they 

 were during the ice-period. 



If we adopt the theory that these glacial conditions 

 were due to eccentricity, then we have, as I endeavoured 

 to show many years ago,* a clue to the probable 

 absolute date of the Middle Eocene and the Upper 

 Miocene periods. There were, as we have seen, two 

 epochs during the Tertiary period when the eccentricity 

 was exceptionally high, viz., 2,500,000 years ago and 

 850,000 years ago. The former might probably be the 



* "Phil. Mag.," November, 1868; 'Climate and Time,' chap. 



