CHAPTER XXIII 

 THE ICE AGE 



FOR some reason or reasons concerning which there 

 has been a great deal of speculation but not a 

 large amount of agreement, the closing stages of 

 the last geologic era which precedes our own and which 

 links the great past to the present, were distinguished by 

 great cold and by widespread fields of ice. Ice-sheets 

 spread over six or eight million square miles of the earth's 

 surface where not long before mild climates had prevailed. 

 Were it not for this great Ice Age and for its far-reaching 

 effects on the conditions under which Man has developed, 

 this period, which is sometimes called the Pleistocene, 

 (from Greek words meaning the "most recent*"), would 

 be more properly joined to the era which we have just 

 been discussing, the two periods constituting a single 

 period of great land elevation and of ocean-shrinking. 

 This period, however, is now thought to be much more 

 important than it was formerly, and perhaps longer in 

 duration. 



More than half the ice-covered land lay in North 

 America and more than half the rest in Europe. The 

 glaciation, therefore, was probably confined to certain 

 parts of the world and did not stretch all over the planet. 



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