MICHIGAN ACADEMY OF SCIENCE. 



31 



what is known as the Fort Wayne Ontlet. (Fig. 3.) Diiring; and prior 

 to the development of a hirge moraine, the Detiance, which forms a loop 

 in the Manmee basin southwest of Lake Erie, and is cut through by 

 Maumee River below Defiance, Ohio, the glacial lake Mamnee had a 

 small area in southwestern Ohio and northeastern Indiana and a nar- 

 row strip in Michigan southwest of Adrian. 



As the ice melted back from the Defiance moraine the lake expanded 

 over the Ioav country to the east and became extended northward on 

 the eastern slope of the Thumb of Michigan^ as far as Imlay. Here 

 it found an outlet across the Thumb and drained past Flint and Duraud 

 into the Grand Kiver and thence to Lake Chicago, its course being along 

 the ecige of the Saginaw ice lobe nearly to Grand River. (Fig. 4.) 



Pig. 4. Lake Maumee and Lake Chicago, witli correlative ice border. 



At present the bed of the channel at the head of the Imlay Outlet 

 stands 45 to 50 feet higher than the head of the Fort Wayne Outlet 

 largely because of differential uplift of the northern outlet. A compari- 

 son of the altitude of the highest beach of Lake ]Maumee with each of the 

 outlets indicates that the Imlay Outlet probably stood about 15 feet 

 lower than the Fort Wayne Outlet. The summit in its bed is 40 feet 

 below the highest beach, T\'hile the summit in the Fort Wayne Outlet 

 is only about 25 feet below the same beach. The second beach of Lake 

 Maumee is barely high enough to have afforded discharge through the 

 Fort Wayne Outlet, but it stands 20 feet above the head of the Imlay 

 Outlet. The actual difference in level of the highest beach at the two 

 outlets is 60 to 65 feet, being 785-790 feet at Fort Wayne and about 850 at 



^The Thumb of Michigan is the peninsula between Saginaw Bay and the Huron-Erie basin. 



