GLACIAL LAKE ALGONQUIN. 415 



basins was directed chiefly to the study of the upper Algonquin and the Nipissing beaches. 

 The importance of faint shore lines was not then fully realized, and comparatively little attention 

 was given to the fainter intermediate lines. The value of the results of that work are somewhat 

 marred, because the measurements were made mostly by aneroid barometer, with a few by 

 hand level in favorable localities. 



Since 1900 the work has been continued in association with Mr. Leverett, who has also made 

 many valuable observations on the Algonquin as well as on the other beaches of this region. 

 Although the Great Lakes history was set apart as the particular theme of the junior author of 

 this monograph, it is a genuine pleasure for him to acknowledge that much valuable advice and 

 assistance and many valuable data have been received by him from the senior author. 



In 1S91 Lawson 1 used the wye level in surveying the abandoned strands of the north shore 

 of Lake Superior, but he assumed horizontality for all the beaches. Continuous tracing is 

 impossible in the region in which he was working, and he appears to have made no attempt 

 to identify any individual beach from place to place by its strength or other characteristics. 

 This was done later by the present writer for one beach — -the Nipissing — first from a study of 

 Lawson's results and later independently. 2 Ultimately, when some of the higher beaches in 

 Lawson's series are identified with individual beaches farther south, his results will be joined to 

 the other areas of accurately measured beaches, and will furnish the data needed for the north 

 shore of Lake Superior. 



Lane and his assistants, Gordon, Davis, Cooper, and Gregory, made some studies on the 

 Algonquin beach in Michigan. 3 Russell studied the Algonquin beach on the southern part of 

 the northern peninsula. 4 



The Toleston beach of Lake Chicago was in all probability reoccupied by Lake Algonquin. 

 This beach has been studied in detail by W. C. Alden in the vicinity of Chicago and also of 

 Milwaukee. 5 



Goldthwait made many wye-level measurements on the Algonquin and lower beaches in 

 Wisconsin in 1905 for the Geological Survey of that State, in western Michigan in 1907 for the 

 United States Geological Survey, and in southwestern Ontario in 1908 for the Canadian Geological 

 Survey, under the writer's direction in both the latter fields. Goldthwait's results have been 

 published in several papers 6 and will be used later in connection with the discussion of the 

 deformation of the old water planes. 



SUBDIVISIONS OF THE BEACHES. 



The beaches of the Port Huron-Chicago stage fall naturally into three groups. 



The upper group comprises the highest beach ridge and several other strong ones and a few 

 faint ones close below. These beaches are set close together in a compact group with small ver- 

 tical intervals. South of the hinge line the Nipissing and Algonquin beaches he close together, 

 the Nipissing being only about 10 feet below the Algonquin. This interval of 10 feet and the 

 beaches in it are all that visibly represent Lake Algonquin in the area of horizontality. As the 

 upper beaches rise north of the hinge fine, the interval becomes wider and the number of strands 

 increases. The interval opens out at first very gradually and for some distance appears to be filled 

 mainly with strands belonging to the upper group. North of Au Sable River the upper group 

 begins to be distinct, and beyond Harrisville it is clearly separated from the lower groups. Where 



1 Lawson, A. C, Sketch of the coastal topography of the north shore of Lake Superior, with special reference to the abandoned strands of Lake 

 Warren: Twentieth Ann. Kept. Minnesota Geol. Survey, pp. 2S2-2S9 and table facing p. 2S0. 



2 Am. Geologist, vol. 15, 1895, pp. 304-314. Also vol. 20, 1S97, pp. 111-128. 



a Chiefly in reports of Michigan Geological Survey on Sanilac, Huron. Tuscola, and Bay counties; see Bibliography, pp. 33-54. Also Pleistocene 

 beaches of Saginaw County: Tenth Ann. Rept. Michigan Acad. Sci., 1908, pp. 90-98, by W. F. Cooper; Report on Tuscola County, by C A. Davis, 

 1908; Report on Arenac County, by W. M. Gregory, 1912. 



< Ann. Rept. Michigan Geol. Survey for 1904, pp. 39-105. 



5 Chicago folio (No. 81), Geol. Atlas U. S., U. S. Geol. Survey, 1902; also Milwaukee folio (No. 140), 1906. 



6 Correlation of the raised beaches on the west side of Lake Michigan: Jour. Geology, vol. 14, 1906. pp. 411-424. Abandoned shore lines of eastern 

 Wisconsin: Bull. Wisconsin Geol. and Nat. Hist. Survey No. 17, 1907. A reconstruction of water planes of the extinct glacial lakes in the Lake 

 Michigan basin: Jour. Geology, vol. 16, 190S, pp. 459—176. Preliminary report on measurements of altitude of the Algonquin and Nipissing shore 

 lines in Ontario: Summary Rept. Director Geol. Survey Canada for 1908. 1909, pp. 112-114. An instrumental survey of the shore lines of the extinct 

 Lakes Algonquin and Nipissing in southwestern Ontario: Department of Mines, Geological Survey Branch Memoir No. 10, 1910. 



