I Ml. CLYDE SERIES OF SOILS. I 
was increased, covering what is now the southern end of Lake Michi- 
gan. In consequence, only .small areas of glacial lake material now 
form the land surface around the southern extremity of that lake. 
In the case of Lake Maumee the gradual recession of the ice gave 
rise to the formation of glacial lake materials covering an area 
of more than 4,000 square miles in northwestern Ohio, northeastern 
Indiana, and southeastern Michigan. In fact, the entire Maumee 
Basin and the adjacent territory, extending from the vicinity of 
Fort Wayne, Ind., past Sandusky, Ohio, on the south and to the 
vicinity of Port Huron, Mich., on the north, was occupied by a suc- 
cession of glacial lakes whose characteristic topography and dis- 
tinctive soils now constitute the principal surface features of that 
region. 
At the same time a considerable area of low-lying land to the 
south and west of Saginaw Bay, in Michigan, was occupied by glacial 
lake waters at several successive periods. It is probable that the 
total area formerly occupied by glacial lake waters around Saginaw 
Bay amounts to approximately 2,500 square miles. 
A similar area was occupied by glacial lake waters standing at the 
lower levels around the head of Green Bay, in Wisconsin, and south- 
west past Fond du Lac. The total area of glacial lake sediments in 
the latter region is possibly as great as 1,000 square miles. 
During these earlier stages of ice recession and glacial lake occu- 
pation the outlets for the ponded waters were through the Des Plaines 
River into the Illinois River, for Lake Chicago; past Fort Wayne 
into the Wabash River, for the first Lake Maumee; and around the 
" thumb " of Michigan through Lake Saginaw and thence down the 
Grand River to Lake Chicago for the more northern waters. As the 
ice still farther receded, a passage for the impounded water was un- 
covered to the eastward between the ice front and the higher lying 
plateau country of northwestern Pennsylvania and western New 
York. For a time, at least, an outlet was established through the 
Mohawk Valley, while at a later stage the drainage way through 
the St. Lawrence River was uncovered. Still later, marine waters 
occupied the St. Lawrence Valley and a small area around the outlet 
of Lake Ontario. Thus a series of glacial lakes was formed along 
the southern shores of Lakes Erie and Ontario and within the St. 
Lawrence Valley. 
FORMATION OF GLACIAL LAKE DEPOSITS. 
During all of these successive stages of glacial lake occupation, 
distinctive lake sediments were deposited at the different levels, de- 
scending from an altitude of about 800 feet for the higher stages of 
the more western lakes to the present level of the upper Great Lakes. 
In the more eastern areas south of Lake Ontario the elevated plateau 
