42 S THE ILLINOIS GLACIAL LOBE. 



to be occupied by glacial lakes. While the ice sheet was covering the 

 present outlets of Lakes Superior and Michigan, these lakes had no connec- 

 tion with each other, nor with the lakes to the east, and their discharge was 

 southward or southwestward into the Mississippi, from the present heads of 

 these lakes. A small district west of Lake Erie was also occupied by a 

 lake that discharged southwestward to the Wabash. Upon the withdrawal 

 of the ice sheet from the southern peninsula of Michigan and the southern 

 portion of the Lake Huron Basin, the lake at the western end of Lake Erie 

 became expanded and a line of discharge was opened eventually from 

 Saginaw Bay across the southern peninsula of Michigan to the Lake Michi- 

 gan Basin, and this being lower than the outlet to the Wabash, that outlet 

 was abandoned. The waters of the Lake Huron Basin being held at a 

 somewhat higher level than those of the Lake Michigan Basin, the flow of 

 water was from the former to the latter. The glacial lake which discharged 

 across the southern peninsula of Michigan extended over the district between 

 Lake Huron and Lake Erie, as well as the Lake Erie Basin and the low 

 district bordering it on the south and west. It apparently did not extend 

 far into the Ontario Basin, as a study of moraines indicates that the ice sheet 

 occupied that basin at the time of this discharge. It thus appears that the 

 Chicago Outlet at one time was the line of discharge for an area much larger 

 than the present Lake Michigan Basin. 



Three well-defined beaches have been recognized at the southern end 

 of the Lake Michigan Basin above the level of the present beach, which 

 are known as the Upper or Grlenwood beach, the Second or Calumet 

 beach, and the Third or Tolleston beach. 



THE UPPER OR GLENWOOD BEACH. 



This beach receives its name from the village of Grlenwood, on the 

 Chicago and Eastern Illinois Railroad, a few miles south of the limits of 

 ( 'hicago. The name has been selected (1) because the beach is especially 

 well developed at that village, and (2) because, being near the State hue of 

 Indiana and Illinois, the name will be familiar to residents of either State. 



In the Illinois portion of Lake Chicago this beach is present, except 

 lor a few miles between Waukegan and Winnetka, where the lake shore is 

 now farther west than it was at the time this beach was formed. In 

 Indiana the beach is present throughout the entire extent of the border of 



