192 A. P. Coleman — Lower lluronian Ice Age. 



If the evidence given above is accepted, the occurrence of 

 glaciation is probable over an area too large to be the work of 

 merely local mountain glaciers, and one must assume the pres- 

 ence of ice sheets comparable to those which formed the 

 Dwyka. 



The Lower Huronian is the second formation in the geolog- 

 ical succession in North America, only the Keewatin coming 

 before it ; so that the probable action of ice on a large scale is 

 pushed back almost to the beginning of known geological 

 time. This implies that the climates of the earlier parts of 

 the world's history were no warmer than those of later times, 

 and that in Lower Huronian times the earth's interior heat 

 was not sufficient to prevent the formation of a great ice sheet 

 in latitude 46°. 



The bearing of these points on early geological history and 

 on theories of the earth's origin is self evident. 



It should be kept in mind, however, that the evidence, 

 though favorable and in some directions strong, is scarcely 

 wide enough to give certainty in a matter of so much theoret- 

 ical importance. 



