EDITORIAL 79 



term Laurentide glacier was intended to designate an ice-sheet 

 developed upon the entire Laurentian })lateau or protaxis — the 

 Canadian shield of Suess — which extends itself, as a relatively 

 elevated tract of U-shaped form around the depression of 

 Hudson Bay, from Labrador on the east to the Arctic Ocean 

 near the mouth of the Mackenzie on the west. 



Mr. Tyrrell's investigations relate particularly to that arm of 

 the protaxis which lies to the west of Hudson Bay, and upon 

 the northern part of this he has been able to define a center 

 of dispersion of glacier-ice to which he has applied the name 

 " Keewatin glacier." He suggests that the name Laurentide 

 glacier may now be relegated to the similar center of radiation of 

 ice shown b}- Mr. A. P. Low to have existed on the Labrador 

 peninsula, and supposes that ice from the latter gathering-ground 

 (at a date subsequent to that of the greatest spread of the Kee- 

 watin glacier) crossed the southern part of Hudson's Ba}- to the 

 Winnipeg basin as well as to that part of the continent in the 

 vicinity of the Great Lakes. It is, however, tacith' assumed 

 that no general occupation of the Laurentian plateau by glacier- 

 ice occurred at a period antecedent to that in which the Kee- 

 watin glacier became defined; although, to the writer, it seems 

 probable that at one time this plateau or axis was thus covered 

 by ice in all its length and that this ice moved down from higher 

 to lower levels in conformity with the normal slope in all direc- 

 tions. 



A second assumption (to which, however, several writers on 

 this subject besides Mr. Tyrrell have given credence) is that 

 implied in the suggested passage of glacier-ice originating in the 

 Labrador region across the watershed to the north of the Great 

 Lakes. The actual evidence on this point appears to the writer 

 to be slight and inconclusive in its nature. Our knowledge of 

 the rocks of the great region involved is, it is believed, insuffi- 

 cient to prove that any erratics from the basin of Hudson Bay 

 have actually crossed this watershed to the south or southwest. 

 Nor can the observed directions of striation be taken as 

 definitely indicating ice-movement in a southerlv sense in all 



