234 ISLAND LIFE 



prevailed. As many reasons combine to make us fix the 

 height of the glacial epoch at the period of high excen- 

 tricity which occurred 200,000 years back, and as the Plio- 

 cene period was probably not of long duration, w^e must 

 suppose the next great jDhase of very high excentricity 

 (850,000 years ago) to fall within the Miocene ei^och. 

 Dr. Croll believes that this must have produced a glacial 

 period, but we have shown strong reasons for believing 

 that, in concurrence with favourable geographical condi- 

 tions, it led to uninterrupted warm climates in the 

 temperate and northern zones. This, however, did not 

 prevent the occurrence of local glaciation wherever other 

 conditions led to its initiation, and the most powerful of 

 such conditions is a great extent of high land. Now we 

 know that the Alps acquired a considerable part of their 

 elevation during the latter part of the Miocene period, 

 since Miocene rocks occur at an elevation of over 6,000 

 feet, while Eocene beds occur at nearly 10,000 feet. But 

 since that time there has been a vast amount of denuda- 

 tion, so that these rocks may have been at first raised much 

 higher than we now find them, and thus a considerable 

 portion of the Alps may have been more elevated than 

 they are now. This would certainly lead to an enormous 

 accumulation of snow, which would be increased when 

 the excentricity reached a maximum, as already fully 

 explained, and may then have caused glaciers to descend 

 into the adjacent sea, carrying those enormous masses of 

 rock which are buried in the Upper Miocene of the Superga 

 in Northern Italy. An earlier epoch of great altitude 

 in the Alps coinciding with the very high excentricity 

 2,500,000 years ago, may have caused the local glaciation 

 of the Middle Eocene period when the enormous erratics 

 of the Flysch conglomerate were deposited in the inland 

 seas of Northern Switzerland, the Carpathians, and the 

 Apennines. This is quite in harmony with the indic- 

 tions of an uninterrupted warm climate and rich vegetation 

 during the very same period in the adjacent low countries, 

 just as we find at the j^resent day in New Zealand a 

 delightful climate and a rich vegetation of Metrosideros, 



