8o EDITORIAL 



cases, for at the time of observation of many of these, it cannot 

 be doubted that a southerly rather than a northerly motion was 

 naturally assumed, in consequence of hypotheses then unques- 

 tioned, and without the critical examination called for in view of 

 later discoveries. So great an extension of an ice-sheet origi- 

 nating on the Labrador peninsula, is all the more doubtful in the 

 light of Mr. Chalmer's investigations, which show that no glacier- 

 ice from the northward crossed the highlands to the south of the 

 St. Lawrence below Quebec. These highlands developed in 

 New Brunswick and northern Maine, an independent center of 

 dispersion, which Mr. Chalmers suggests may be referred to as 

 the Appalachian system of glaciers or the Appalachian glacier.^ 

 If, therefore, we may admit the existence of a Laurentide glacier 

 of early date and such as to envelop the whole Laurentian 

 plateau, the Keewatin glacier of Mr. Tyrrell, with that which 

 may be named the Labradorian glacier,^ as known to us by Mr. 

 Low's work, may be regarded as relatively local ( although still 

 very important) centers of dispersion connected with a dimin- 

 ishing stage of the glacial period. In this case the overriding 

 of the area at one time covered by the southward extension of 

 the Keewatin glacier by ice from the eastward ( as demonstrated 

 by Mr. Tyrrell ) may be attributed merely to a still later reex- 

 tension, due to climatic changes, of that part of the Lauren- 

 tide glacier situated to the east of Lake Winnipeg. If, on the 

 other hand, it should ultimately be shown that no continuous 

 ice-sheet ever covered the entire length of the Laurentian pla- 

 teau, the several great glacier masses actually known to have 

 been developed upon these highlands may still be appropriately 

 considered as constituting together a Laurentide group, as 

 distinguished from the great western Cordilleran ice-mass. 



In the case of the Keewatin and in that of the Labradorean 

 glacier, it has been shown by Messrs. Tyrrell and Low that the 

 centers of dispersion changed, giving rise to superposed series 

 of striations, and it appears probable that in the study of this 



' American Geologist, Vol. VI (1890), p. 325. 



- This has, I believe, already been proposed by Mr. F. B. Taylor. 



