T H li GLACIAL LAKES 



crowded the channel westward. In this stage the lake reached 

 its greatest extent. (ligure 5.) Curiously, it was lower than 

 the hrst Lake Maumee but higher than the second, and 

 stretched from Fort Wayne, Indiana, northward to Imlay 

 City, Michigan, and eastward to Girard, Pennsylvania. The 

 outlet continued through Grand River to the small Lake 

 Chicago in the Michigan basin, and thence to the Mississippi. 

 The ice front extended from the vicinity of Detroit across the 

 basin of Lake Erie, at a distance of forty or fifty miles east of 

 Toledo, so that along the ice the lake was 1 50 to 200 feet deep. 

 As the ice formed the eastern and northern shores, the lake 

 made no beach lines in Ontario. 



Figure 6 shows diagrammatically the stages of Lake Mau- 

 mee and of the later lakes which occupied the Erie basin in 

 its step-like descent to its present level. From the highest to 

 the lowest is over 270 feet. 



Lake Saginaw 



During the final stages of Lake Maumee the ice in the 

 Saginaw Bay depression had retreated far enough so that a 

 small shallow crescent-shaped lake was formed along its 

 margin. This lake, known as Saginaw (Figure 5), became 

 larger when it received the overflow drainage from the Imlay 

 outlet river, and the waters of Lake Maumee and Lake Sagi- 

 naw flowed past the site of Maple Rapids into Grand River, 

 thence to Lake Chicago through a series of small lakes back 

 of the lake-border moraine near Paw Paw and Dowagiac, 

 Michigan. Lake Chicago also slowly expanded as the ice in 

 the Lake Michigan lobe melted northward. At first the chan- 

 nel of Grand River was narrow, but gradually, as the flow 

 from the lakes entered and scoured it, this became one of the 

 mightiest streams of the North American continent — a mile 

 to one and one-fourth miles wide and, near Grand Rapids, a 

 hundred and twent\' feet deep. 



39 



