EXCURSIONS OF AN EVOLUTIONIST 



began 880,000 years ago corresponded with a 

 glacial epoch in the Miocene period, and that 

 in like manner the date of 2,650,000 years ago 

 witnessed the beginning of a great glacial epoch 

 in the Eocene period. But these conclusions are 

 not generally adopted by geologists. There are 

 some evidences of local glaciation in the Miocene 

 period in the neighbourhood of the Alps, which 

 were probably higher then than they are at pre- 

 sent, but the weight of evidence is entirely in fa- 

 vour of the conclusion that the general climate 

 of Europe throughout the Eocene and Miocene 

 periods was much warmer than it has been at 

 any later date. From the Eocene period down 

 to the Pleistocene, there can be little doubt that 

 there was a slow but steady lowering of the mean 

 temperature of Europe, until in the latter period 

 there occurred that comparatively rapid refrig- 

 eration which brought about a glacial epoch. 

 In earlier than Tertiary times, on the other 

 hand, Mr. Croll seems to have been more suc- 

 cessful. There are distinct and numerous evi- 

 dences of extensive glaciation in Europe dur- 

 ing the remote Permian period ; and it is not 

 improbable that similar phenomena may have 

 taken place in Silurian times. On the whole, 

 however, it does not seem likely that there 

 have been many periods of extreme glaciation, 

 like that which we suppose to have ended about 

 80,000 years ago ; and it is quite unlikely that 

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