240 The American Geologist. April, 1896 
Probably the view presented by Mr. Taylor is true for the 
early stage of lake Warren when it was forming the Belmore, 
Ridgeway, or Sheridan beach in the Erie basin; and this IV- 
wanio lake may be accepted as enduring until the continued 
glacial recession uncovered the strait of Mackinaw. Such 
correlation seems consistent with Spencer's recorded observa- 
tions of beaches east and west of the Pewamo outlet.* if tin- 
country from Pewamo eastward and from Ypsilanti northeast- 
ward to Imlay has since been differentially uplifted, and if 
the beach noted on the west in the vicinity of Columbia and 
Allegan, Mich., is referable to the high earliest stage of the 
glacial lake Michigan before deep erosion of its outlet and 
northeastward uplifting together sufficed to bring the Pe- 
warno-Saginaw watershed above that outlet past Chicago to 
the Des Plaines and Illinois rivers. During the Pewamo stage 
of lake Warren, the glacial lake expanding northward in the 
basin of lake Michigan as the ice retreated may have held the 
level of its lowest raised beach at Chicago, only 15 feet above 
the present lake. 
When the strait and island of Mackinaw became uncovered 
from the ice, one sheet of water is thought by the' present 
writer to have extended over the four upper Laurentian 
lakes. f The former lake Warren or Pewamo. of the Erie-Hu- 
ron area, fell about 45 feet, as measured at Cleveland by the 
vertical interval between the Belmore beach and the Arkona 
or upper Crittenden beach, the first formed in the Erie basin 
on a level with the Chicago outlet. After further northeast- 
ward uplift of the country, the far extended and chief stage 
of lake Warren appears to have long held, on the south side of 
lake Erie, the level of the Forest or lower and principal Crit- 
tenden beach, 20 feet below the Arkona level, and about 100 
feet above the present lake Erie. During the Arkona and 
Forest stages lake Warren seems to me to have formed the 
high shore lines of Mackinaw island, of Green bay, of the 
northern part of lake Huron, Georgian bay, and lake Nipis- 
sing, and of lake Superior, excepting the still higher beaches 
of the earlier Western Superior glacial lake from Marquette 
*Am. Jour. Sci., Ill, vol. xli, pp. 201-211, with map, March, 1891. 
jGeol. and Nat. Hist. Survey of Minnesota, Twenty-third Annual Re- 
port, for 1894, pp. 15G-193, with map; also Am. Jour. Sci., Ill, vol. xlix, 
pp. i-18, with map, Jan., 1895. 
