Correspondence. 397 
ing its departure in the closing or Champluiii epoch of the Ice age, with 
citations of the voluminous literature of this subject. The map which 
accompanied that paper is reprinted in the May Ameuican Geologist 
as Plate X, delineating provisionally seven stages of the ice-sheet, from 
its maximum extent to the time, late in the process of the ice departure, 
when the sea appears first to have found an avenue of inflow to the St. 
Lawrence and Ottawa valleys and the basin of lake Champlain by the 
melting away of the glacial barrier across the present course of the 
St. Lawrence in the vicinity of Quebec or farther northeast. The 
high Pleistocene shores from lake Superior to lake Ontario, and the 
highest shores above the marine beds eastward, seem to me to be clearly 
referable to glacial lakes; and for comparison with the opinions of 
Spencer, Taylor, and Lawsoii, the sequence of events represented in 
Plate X by the seven stages of culminating and waning glaciation is 
here brought very concisely into review. 
L Greatest e.vtension of the ice-sheet; Mt. Washington and the 
Green and Adirondack mountains enveloped to their summits by the 
continental glacier; its surface thence rising northward across the St. 
Lawrence valley to the Laurentian highlands. The Kansan stage of 
Chamberlin's classification (third edition of the Great Ice Age, 1894, and 
Journal of Geology, vol. in. pp. 270-277, April-May, 1895). 
2. Boundary of the waning ice-sheet at the Altamont moraine, the 
earliest and outermost of the series traced across the northern United 
States, marking pauses or slight readvances which interrupted the gen- 
eral glacial retreat. This time, coming after Chamberlin's intervening 
Aftonian and lowan stages, was at the beginning of his Wisconsin or 
moraine-forming stage. 
3. Maximum area of the Western Su|)erior glacial lake. 500 to (iOO feet 
above the west part of lake Superior, with outlet through northwestern 
Wisconsin by the Bois Brule and St. Croi.x rivers. The glacial lake 
Warren, outflowing past Chicago, reached north along the greater part 
of the basin of lake Michigan; and the Western Erie glacial lake out- 
flowed past Ft.' AVayne to the Wabash river. 
4. Maximum area of lake Warren, 400 to GOO feet above lake Superior 
and the north part of lake Huron and Georgian bay; extending east 
somewhat beyond lake Nipissiiig, and to Crittenden in southwestern 
New York, with shores now raised by differential uplift nearly 300 feet 
above the east end of lake Erie. 
5. Boundary of the ice-sheet [)assing east of lake Xii)issing, thence 
south to the vicinity of Toronto, and east along the north side of the 
Mohawk river. The glacial lake Algonipiin, held by an ice barrier only 
at the lowest passes east of Georgian bay, with outflow south by the St. 
Clair and Detroit rivers, was at first tributary to the very short-lived 
glacial lake Lundy, above the east part of the pri'sent lake Erie, but 
later to the glacial lake Iroquois by the Niagara river, which then be- 
gan its existence and the erosion of the gorge below its n-cediiig water- 
fall. 
(5. Recession of tin- ice-shei'l past the iiortii side of the .Vdirondacks; 
