MICHIGAN ACADEMY OF SCIENCE. 
01 
tween the different sheets of drift all of which have been given a nomenclature 
and it furthermore seems probable that some of these intervals of glacia- 
tion exceeded in time, the period since the last glacial epoch closed. 
Radiating from these ice masses there are along the southern border of 
the last glacial epoch a more or less pronounced lobation of the ice. Thus 
in the area of Lake Superior the Keweenaw and Superior lobes were developed ; 
along the axis of Lake Michigan the Green Bay and Michigan lobes; in the 
Huron-Erie basin the Saginaw lobe and the Huron-Erie lobe. 
Lake History. 
As the ice border withdrew to the north the glacial waters were ponded 
between the ice on the north and land divide to the southward. The history 
of these changes has been described by Chamberlin and Leverett in the 
reports referred to above. In brief, we first have Lake Maumee imponded 
by the Erie lobe and escaping through the lowest available col at Fort Wayne, 
into the Wabash, and thence to the Gulf. In the second stage of Lake 
Maumee consequental to the further retreat of the ice we have the waters 
draining off through the Imlay outlet in the eastern part of Lapeer county, 
around the edge of the Saginaw ice-lobe to the valley of the Grand River. 
Somewhat later Lake Saginaw came into existence, coincident with the 
retreat of the Saginaw glacier and this crescentic lake drained off through 
the Pewamo passage into the Grand River outlet, and thence through Lake 
Chicago and the Illinois route into the Mississippi. During a portion of 
the existence of this Lake Saginaw we have Lake Maumee still discharging 
through the Imlay outlet into Lake Saginaw but later on in the retreat of 
the ice, a lower outlet across the “thumb” of eastern Michigan was opened 
and the Imlay outlet was abandoned. 
Later on we have Lake Arkona with the Belmore beach and Lake Whittle- 
sey the resultant of the reaclvance of the ice, discharging through the Ublv 
outlet, and for a time submerging the Arkona beaches which were partially 
obliterated. At a still later stage Lake Warren came into existence, con- 
temporaneous with the withdrawal of the ice from the “thumb” and allowing 
the waters of Lakes Saginaw and Whittlesey to unite. At first the drainage 
was westward through the Grand River valley until the ice retreat to the 
eastward furnished a drainage channel through the Mohawk valley. 
At a still later date Lakes Algonquin and Nipissing came into existence 
consequental to the further withdrawal of the ice. The area of Lake Nipiss- 
ing was very nearly coextensive with that of the present area of the Great 
Lake System. 
Beach Formations. 
During the summer and fall of 1899 and a portion of field season of 1900, 
the writer had an opportunity of obtaining detailed information concerning 
beach formations, which were in course of development during the history 
just sketched. In the summer of 1904 and 1905, Mr. Charles Holmes, for- 
merly County Surveyor of Saginaw, ran 1339 miles of levels with the wye 
level and this has given a fine chance to determine the elevation of numerous 
old beach formations with accuracy. In the following account Mr. Holmes’ 
elevations are indicated by a decimal point while my readings taken with a 
good aneroid barometer are only given for feet. In making aneroid adjust- 
ments a graph was determined giving the amount of variation of the instru- 
ment in feet per minute, from which the necessary correction could be made. 
