224 The American Geologist. October. 190.3. 
terminated by the continued melting of the ice-sheet, at last 
allowing the sea to come in past the site of Quebec and to cover, 
at a somewhat lower level, nearly the same area as the previous 
glacial lake, which eight years ago I named lake St. Lawrence.* 
The exact boundaries of both these glacial lakes at 
their earliest and highest stages, are undoubtedly trace- 
able by more or less distinct shore erosion, beach deposition 
of sand and gravel, and deltas of inflowing streams. But these 
evidences of the old shore lines are mostly very dim, for these 
lake areas appear not to have been occupied by tbeir bodies of 
water longer than the lake Agassiz basin, and their usually 
more irregular contour of the inclosing slopes gave less chance 
for coastwise drift and formation of beach ridges. Only at a 
few places have their shores been identified, by Davis, Baldwin, 
and Baron de Geer, with determinations of their altitudes. 
According to my observations, the general absence of any 
considerable lacustrine, deposits, excepting rare and small del- 
tas, which must be searched for by leveling, proves the geo- 
logic brevity of the duration of these lakes. Their existence 
could have measured only a very small fraction of the period of 
the great Quaternary lakes Bonneville and La Hontan, with 
their conspicuous shore terraces and thick lacustrine sediments. 
Instead, the lakes Hudson-Champlain and St. Lawrence evi- 
dently belong in the same class, in respect to their duration, 
with the other great glacial lakes of the Laurentian drainage 
area, as lakes Iroquois, Algonquin, and Warren, and with lake 
Agassiz, for which last I have estimated a duration equal to no 
* "Late Glacial or Chainplain Subsidence and Ke elevation of the St Law- 
rence River Basin," Geol. and Nat. Hist. Survey of Minnesota. 23d Animal Re- 
port for 1894 (published 18951, pp. 156-193. with map; also partly in Bulletin 
Geol. Soc Amer.. vol. vi, pp. 21-27, Nov., 1894, and Am. Jour. Sci., third series, 
vol. xlix, pp. 1-18, with map, Jan., 1895. 
Sir J. WK.LUH Dawson, The Canadian Ice Age (Montr al, 1893). pp. 
301 , with maps and sections, views ot scenery, and nine plates of Pleistocene 
fossils. This volume sums up the author's work from 18."5 on the glacial drift 
and associated lacustrine and Champlain marine formations oi the St. Law- 
rence valley, embodying the studies which had been published in many papers 
in the "Canadian Naturalist and Geologist" and elsewhere. He had given a 
similar summarv in a pamphlet of 112 pages, "Notes on the Post-pliocene of 
Canada," in 1872. 
G. K. Gilbert, "Changes of Level of the Great Laks," in The Forum, vol. 
v, pp. 4,17-4.28. June, 1888; "History of the Niagara Kiver." Sixth Annual Re- 
port, Commissioners of the State Reservation at Niagara, for 1889. pp. 61-84, 
with eight plates (also in the Smithsonian An. Rep. for 1890, pp. 231-2571. 
J. W. Sprncer. "\ Review of the History of the Great Lakes." Amer. 
Geologist, vol. xiv, pp. 289-301, Nov., 1894 (containing citations of many 
earlier papers by Prof. Spencer and others. 
Baron de Geer, S. Prentiss Baldwin, and Warren Upham, as before 
cited for Lake Hudson-Champlain. 
