History of lake Agassis. — Upliam. 191 
ice-front appears to have become again lobate, extending from the 
west shore of lake Agassiz southward and then westward and 
northward, between the lake area and the Sheyenne river, to the 
prominent and typical moraines that are found south of Stump 
and Devil's lakes, on the Big Butte, about Broken Bone lake 
and northward, and on Turtle mountain. In their remarkable de- 
velopment these moraines are similar to the massive Leaf Hills, 
with which they seem to have been contemporaneous. 
The course of the ice front where it formed the northern barrier 
of lake Agassiz, at the time of its accumulation of these great 
moraines of the Leaf Hills and the south side of Devil's lake, is 
marked by morainic deposits both east and west of the lake near 
the latitude of 47° 10', which passes twenty miles north of Fargo, 
by an unusual abundance of boulders near this latitude and far- 
ther north on portions of the till forming each side of the lacus- 
trine area ; and by a tract of till which stretches across the Red 
River valley at Caledonia, constituting the bed and banks of the 
river along the Goose rapids. In the lake this morainic till was 
spread with a generally even surface, but it has many small in- 
equalities, the higher portions being three to five feet or rarely ten 
feet above adjoining hollows. Boulders and gravel are plentiful 
on its surface, this being the onl}- interruption of the lacustrine 
and alluvial clayey silt which elsewhere continuously occupies the 
central part of this valley plain from near Breckenridge to Win- 
nipeg. 
Toward the east the ice-sheet at this time had receded from the 
southwest part of lake Superior, which was held about 500 feet 
higher than now and overflowed to the Saint Croix and Mississippi 
rivers by the way of the Bois Brule river and Upper Saint Croix 
lake. It seems nearly certain also that the ice-border continued 
across Green bay and the north part of lake Michigan ; and fur- 
ther east, I think that it probably crossed southwestern Ontario 
and the central or northern portions of New York, Vermont, New 
Hampshire, and Maine. The Laurentian lakes were dammed l>v 
the retreating glacial barrier and overflowed at the lowest points 
on their southern water-shed. 
During the formation of the tenth or Itasca moraine, crossing 
the lake region at the head of the Mississippi, the ice-sheet bound- 
ing lake Agassiz probably extended thence northward, passing 
