206 Cauon Tristram on the Polar Origin of Life. 



contrary, never going far from the open sea to breed, com- 

 mingled very little, if at all, Avith their congeners from the 

 other oceans, and their conditions of life being identical, 

 whether in the Atlantic or Pacific, the changes were but 

 slight in corresponding species of either ocean, notwith- 

 standing their segregation in their breeding haunts. 



Meanwhile, as the Polar continent continued to cool, the 

 accumulation of snow and ice over its whole surface became 

 so enormous from the precipitation of frozen vapour, as to 

 equal the present deposits on the Southern Polar continent. 

 The continuous land area prevented the circulation of the 

 equatorial currents round the Pole. This was going on 

 throughout the Pliocene era. The glaciers pushed down 

 across the Atlantic in the latitude of the British Isles, and 

 formed a complete barrier from America to Europe. At 

 length the superincumbent mass on the Polar continent 

 pressed down that area below the sea-level, with the excep- 

 tion of the higher lands, which became islands. The glaciers 

 sank to the edge of the ocean. The equatorial current did 

 its work ; the ice-blocks became detached, the ancient land 

 behind them was now submerged. The warm Atlantic 

 stream burst in towards the Pole, and the glacial epoch 

 gradually melted away. But with this influx of warmer 

 water, the submerged land, relieved of its superincumbent 

 weight, gradually began to rise again wherever touched by 

 the equatorial current. This process we see going on before 

 our eyes in the elevation of Scandinavia, and the still more 

 rapid upheaval of Spitsbergen, Grinnel Land, the Parry 

 Archipelago, and Novaya Zemlya which has risen 100 feet in 

 less than 300 years. Meanwhile Greenland, struck by the 

 Polar instead of the equatorial current, and overpowered by the 

 Mcight of its glaciers and ice-deposits, is as steadily sijiking. 

 But this process of the glacial epoch, with the phenomena 

 and results of which we are so familiar, appears to have been 

 confined to the region between Hudson's Bay and the White 

 Sea. There does not seem to be any clear evidence that 

 there was any synchronous period of gelation, either in 

 Northern Asia or in America west of Hudson\s Bay. Geikie 



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