24(S J. W. GOLDTinVAlT^ALGONQUlN AND IROQUOIS BEACHES 



'J'he rough parallelism of the isol)ases Avith the glacial houndar}^ on the 

 one hand, and with the horder of the pre-Cainhrian oldland of Canada 

 on the other, in connection with the marked increase of tilt rate near the 

 latter boundary, seems to strengthen the position taken by De Geer*" 

 twenty years ago, that in North America, as in Scandinavia, the central 

 areas of the recent npwarpings were not merely centers of glaciation, but 

 centers of continental nplifts of much earlier dates. 



^ In his view regarding the central area of uplift in Canada, De Geer followed 

 Spencer, who as early as 1889 attempted to locate the precise center of post-Algonquin 

 upwarpings in a paper "On the focus of regional post-Glacial uplift" (Transactions of 

 the Royal Society of Canada, section 4, vol. 7, 1889, p. 129). Spencer reached the con- 

 clusion that the center or focus was on the height of land southeast of James' Bay. 

 De Geer's isobases are concentric with that point. In view of the subsequent discovery 

 of the far westward trend of the isobases of Lake Algonquin and i^ake Agassiz, it now 

 appears that if the uplifts centered around any one point, that point was much farther 

 north than Doctor Spencer supposed, or that the uplifts centered along an axis which 

 trends westward from his "focus." 



