LAKE IROQUOIS. 775 



has recently been supplemented by Coleman's discovery of fresh-water shells 

 in the Iroquois beach near Toronto. It now seems well established that 

 Lake Iroquois stood nearly 200 feet above sea level. 



This determination is of value in working out the altitudes of the glacial 

 lakes which preceded Lake Iroquois. It follows that Lake Warren, which 

 stood about 450 feet above Lake Iroquois had an altitude not far from 650 

 feet above the sea, while Lake Whittlesey stood slightly over 700 feet, and 

 Lake Maumee at its highest stage stood about 750 feet. These altitudes are 

 but 30 to 40 feet lower thau the present altitudes in the western 23art of 

 the Lake Erie Basin, and covering, as they do, several lake stages, they bear 

 testimony to long-continued stability in that region. 



Note. — In eastern Michigan A. C. Lane has found a well-defined beach about 

 50 feet below the lowest of the Lake Warren beaches, or 690 to 700 feet above tide, 

 which he has named the Grassmere beach. About 20 to 30 feet below the Grassmere 

 is a fainter shore line which he has named the Elkton beach.' W. H. Sherzer has 

 recognized the Grassmere beach in southeastern Michigan, and has traced it a short 

 distance into Ohio. It there stands between 610 and 620 feet above tide, or about 40 

 feet above Lake Erie. He finds the lowest Lake Warren shore to be below the 660- 

 foot contour.^ The Grassmere beach maj^ be a continuation of the beach at Derby, 

 N. Y., noted on page 77-3, but as yet the plain south of Lake Erie has not been exam- 

 ined with sufiicient thoroughness to warrant an opinion. In eastern Michigan and 

 in the adjacent part of Canada a strong beach known as the Algonquin appears at the 

 south end of Lake Huron at a level onlj' a few feet above the present lake surface, 

 but northward it rises to a much greater altitude.' The Algonquin beach of the 

 Huron basin, it is thought, may be of similar age to the Iroquois beach of the Ontario 

 basin, but further study is necessary to insure satisfactory correlations. 



' Geol. Survey Michigan, Vol. VII, 1900, part 2, pp. 73-7.5, PI. VIII. 



2 Ibid., pp. 141-143, PI. VII. 



'J. W. Spencer: Am. Jour. Sci., 3d series, Vol. XLI, 1891, pp. 12-21. 



