GLACIAL LAKES TAYLOR. 327 



Tlie accompanying diagrammatic map (fig. 10) shows the relation 

 of the Wliittlesey and Algonquin hinge lines to the extreme border 

 of the Wisconsin ice sheet, with three later critical positions of the 

 ice border and several of the isobases. The hinge lines and isobases 

 in the regions east and west of the Great Lakes are added in order 

 to show the general relations of the deformations in those parts to 

 that of the region under discussion. The shore lines of the glacial 

 Lake Agassiz are taken from Upham. (Monograph 25, U. S. Geo- 

 logical Survey.) No shore lines in the Great Lakes area are shown 

 excepting the Glenwood or highest beach of Lake Chicago, the 

 Whittlesey beach, and the correlative beach of Lake Sagmaw. The 

 two hinge lines for Wliittlesey and Algonquin represent the isobase 

 of zero for each beach. Both are produced conjecturally northwest- 

 ward to the region of the glacial Lake Agassiz. Two Nipissing 

 isobases are shown in the Superior basm, and these show a trend 

 quite different from those of the Algonquin. In the Michigan and 

 Huron basins the Nipissing beach seems to hinge on about the same 

 line as the Algonquin. The curved isobases in the region south of 

 St. Lawrence River and east of Lake Ontario show the present state 

 of knowledge concerning the deformation of the marine shore Une. 

 They show the general relation of the deformation of the marine area 

 to that of the Great Lakes region. The extent of the pre-Cambrian 

 or Old-land area is also indicated to afford means for comparing it 

 with the area of uplift. Inasmuch as the uplift occurred m the course 

 of the melting of the Wisconsin ice sheet and relief from the ice load, 

 and inasmuch as it lies so largely witlun the glaciated district, a 

 causal relation has by some been inferred and definitely announced. 

 The writer would caution against too hasty conclusions m this matter, 

 especially in view of somewhat discordant relations between the 

 boundaries of the ice and of the uplifted lands which this diagram- 

 matic map will serve to bring out. The writer will take space here 

 merely to state that the preponderance of present evidence appears 

 to be only slightly in favor of resilience following depression by the 

 ice weight as the main cause of the uplifting of the land and the 

 deformation of the shore lines in the region of the Great Lakes. 

 Standing as a close second to the hypothesis of ice weight is the pos- 

 sibility of deformation of the beaches by uplifts of the land incident 

 to crustal creeping movements, which are simply the most recent 

 impulses in a long process of continental growth reaching back into 

 the Tertiary age. If certain evidences which are now supposed to 

 indicate relatively recent crustal creep toward the southwest are 

 substantiated, the hypothesis of resilience following depression by ice 

 weight seems likely to become of secondary importance. 



