THE ARRIVAL OF MAN IN EUROPE 



tainous, and send down glaciers into the sea ; and 

 as they are exposed to moist sea-air on every side, 

 the precipitation, almost all of which takes the 

 form of snow even in summer, is of course un- 

 usually large." 



In order, therefore, to get a centre from which 

 to start an accumulation of snow and ice suffi- 

 cient to bring on a glacial epoch in the northern 

 hemisphere, it would seem absolutely necessary 

 that there should be a considerable amount of 

 high land within the Arctic Circle. But in the 

 Eocene and Miocene periods this condition 

 does not seem to have been satisfied. Through- 

 out the greater part of these two periods the area 

 within the Arctic Circle was less elevated than it 

 has been ever since the beginning of the Pliocene 

 age. Greenland stood lower than at present, and 

 the greater part of Siberia was submerged. 

 Moreover, as already stated in the preceding 

 paper, the continents of Europe and Asia did 

 not become " united into one unbroken mass " 

 until the Pliocene period. In the earlier Terti- 

 ary times the warm waters of the Indian Ocean 

 flowed northwestward between Asia and Europe 

 even into the Arctic Ocean, the mountains of 

 Armenia and the Caucasus protruding as islands 

 from this vast sea surface. Again, Mr. Wallace 

 has pointed out a number of peculiarities in the 

 distribution of plants and animals in the south- 

 ern hemisphere which " render it almost certain" 



63 



