PHYSICAL AND CLIMATAL CONDITIONS. 93 



north-westward, or a less copious supply of snow in that 

 direction, the latter being the more probable supposition 

 on account of the absence, which has just been referred 

 to, of traces of giaciation in the extreme north-west. 



"The flooding of the great plains by arctic waters 

 while the Cordillera stood as a much-elevated land 

 between them and the warmer waters of the Pacific, 

 would in itself go far to explain the conditions under 

 which the excessive precipitation required for the pro- 

 duction of the great Cordilleran glacier occurred." 



It would appear that there is no evidence of any 

 extensive flow of ice from the Cordilleran glacier to the 

 eastward, though small local glaciers may have moved 

 down to the submerged plains, which, owing to the 

 prevalent westerly winds, could contribute little to the 

 snow on the mountain ranges. It would also appear 

 that the maximum condensation of the Pacific moisture 

 occurred not more than 200 miles inland from the west 

 coast. At the same time, the submergence of the great 

 plains of the St. Lawrence valley and of the eastern 

 coast would place the Laurentide and Appalachian moun- 

 tains under similar conditions, but not of so extreme 

 magnitude. 



We have thus a perfect geographical picture of extensive 

 local giaciation in the early glacial age, in circumstances 

 most favourable for its existence. Let us not forget, 

 however, that this picture belongs only to one portion of 

 the period. There was in the Cordillera also a mid- 

 glacial period of subsidence of the mountain axis, and a 

 later development of smaller local glaciers, the deposits 

 of which have also been worked out by Dr. G. M. Dawson. 



Two very interesting and important series of observa- 

 tions bearing on the giaciation of the eastern part of 



