ENVIRONMENT. PAST AND PRESENT 69 



musk-ox was to be found as far south as Arkansas, 

 walruses besported themselves off the coast of 

 Georgia, while lemmings and mammoths were 

 among the arctic representatives of the fauna of 

 southern France. 



The Pleistocene glaciations are represented in 

 north America by at least four and perhaps five 

 different periods, which take us back about a mil- 

 lion years, while some fifteen to twenty thousand 

 years have elapsed since the close of the last Pleisto- 

 cene ice-age known as the Wisconsin. The ac- 

 companying map shows the extent of the glaciation 

 in the northern hemisphere during the Wisconsin 

 period and during all the other periods combined. 

 The patchy nature of the glaciation in the old world, 

 due largely to the formation of glaciers in connection 

 with the mountain ranges will be immediately 

 noticed. Such glaciation as occurred in the southern 

 hemisphere (apart from Antarctica) during the 

 Pleistocene was of this restricted type. The inter- 

 glacial periods were comparatively mild, some of 

 them milder than our present climate. While not 

 a great deal is known about them it seems certain 

 from recent investigations, chiefly on fossil pollen 

 grains, that in northern Europe the present period 

 is already getting cooler than it was 2000 years ago, 

 quite possibly presaging the approach of yet another 



