THE ICE AGE 



lands in all directions. Then the Rhine glacier moved out 

 far beyond the mountains and joined with the glaciers of 

 Savoy and Dauphiny on the plains of France, while from 

 the Southern Alps glaciers invaded the fertile plains of 

 Italy. 



Glaciers of similar size and extent descended into 

 the valleys of the Rhine and Danube. The Pyrenees, 

 some of the higher mountains of the Spanish plateau, the 

 higher mountains of France, the Apennines, the Carpa- 

 thians, the Balkans, the Urals, all had their ice-sheets. 

 Iceland and the Faroe Islands were buried under ice, and 

 even Corsica had snowfields and glaciers, some of which 

 were not small. 



Nearly one half of North America was buried in ice. 

 Strangely enough, it was not the whole northern half, 

 but the north-eastern half that was specially ice-invaded, 

 and, more strangely still, not so much the mountain- 

 ous portions, though these were affected, as the plains. 

 Alaska was largely free from ice except on or about 

 the mountains: and there was less ice on the western 

 plains than in the valley of the Mississippi. Much the 

 greater part of the four million square miles of ice-field 

 lay on the plains of Canada and in the upper Mississippi 

 valley. The Missouri and Ohio rivers like two great 

 arms embraced the borders of the ice-fields to which they 

 owe their origin. 



We do not propose to examine the several theories 

 which have been proposed to account for this extra- 

 ordinary cold, for none is completely acceptable or ac- 

 cepted, but we may just mention them. Dr. Croll a 



271 



