History of lake Agassiz. — Upham. 189 
ward to the Mississippi and finally eastward to the Mohawk and 
Hudson.* 
In tracing the history of lake Agassiz it will be needful to re- 
view the recession of the ice- sheet which was its northern barrier, 
as the stages of that recession are shown b}- the successive termi- 
nal moraines of Iowa, Minnesota, South and North Dakota, and 
Manitoba ; to observe the stages of the lake itself which are re- 
corded in its successive beaches ; and to note the contemporaneous 
history of the glacial lakes on the west, whose outflow b} T the 
Sheyenne, Pembina, and Assiniboine brought large deltas into the 
western edge of lake Agassiz and spread deposits of fine silt over 
extensive areas of its bottom. 
When the latest North American ice-sheet attained its greatest 
area, its southern portion from lake Erie to North Dakota consisted 
of vast lobes, one of which reached from central and western Min- 
• nesota south to central Iowa. This Minnesota lobe in its maxi- 
mum extent ended near Des Moines, and its margin was marked 
by the Altamont moraine, the first and outermost in the series of 
eleven distinct marginal moraines of this epoch which are recog- 
nizable in Minnesota. When the second or Gary moraine was 
formed, it terminated on the south at Mineral Ridge in Boone 
county, Iowa. At the time of the third or Antelope moraine, it 
had farther retreated to Forest City and Pilot Mound in Hancock 
county, Iowa. The fourth or Kiester moraine was formed when 
the southern extremity of the ice-lobe had retreated across the 
south line of Minnesota and halted a few miles from it in Free- 
born and Faribault counties. The fifth or Elysian moraine, cross- 
ing southern Le Sueur county, Minnesota, marks the next halting- 
place of the ice. At the time of formation of the fifth moraine, 
the south end of the ice-lobe had been melted back a hundred and 
eighty miles from its farthest extent, and its southwest side, which 
at first rested on the crest of the Coteau des Prairies, had retired 
thirty to fifty miles to the east side of Big Stone lake and the 
* "Changes of level of the Great Lakes,*' by G. K. Gilbert, in The 
Forum, vol. v, pp. 417-428, June, 1888. Geol. Sur. of Canada, reporl of 
Progress to 1863, pp. 910-915. C. Whittlesey, "On the Fresh-water Gla- 
cial Drift of the Northwestern stales," L864, pp. it-:.". 1 . In Smithsonian 
Contributions, vol. xv. J. S. Newberry in Report of the Geological Sur- 
vey of Ohio, vol. ii, 1874, pp. 50-65, wiili three maps. "The Lake A.ge 
in Ohio,*' by E. W. Claypole, pp. 42, with lour maps, Trans, of the Geol. 
Soc. of Edinburgh, 1887. 
