236 The American Geologist. October, 1895 
at Portland, Maine. The preglacial southern limit of this boreal fauna 
seems to have been a little north of Boston; but its presence later was 
indicated also at Nantucket island, in the upper shell bed of Sankaty 
Head, where the summer temperature was fifteen degrees (Fahr.) colder 
than in the lower beds. 
Northern areas were depressed more than those toward the south, the 
vertical extent of the Champlain subsidence, below the present altitude, 
having V^een .50 to 75 foet near New York city, 300 to 400 feet in Vermont 
and 5G0 feet at Montreal. This leads to the belief that the stratified 
clays in the valleys of our northern rivers, like the Connecticut, were 
deposited during this epoch; and the occurrence of Arctic plants in 
them strengthens this view. At the same time the Laurentide, White, 
Green and Adirondack mountains were covered by local glaciers which 
sent bergs into the enlarged gulf of St. Lawrence, giving to it a severely 
cold climate. Ice floes and bergs from Arctic regions must also have 
entered the Champlain sea, as many of the smaller bergs borne south- 
ward by the Labrador current do now: but far more abundantly than 
at present, because of the greater depth of the water in the Strait of 
Belle Isle. 
Marizie submergence is suggested for all the area of the great Lauren- 
tian lakes, as far as to lake Superior and Minnesota, Ijy the presence 
there of still living maritime plants, fish, and Crustacea. These plants 
and animals appear to require the former presence of the ocean to ac- 
count for their geographic distribution. The glacial conditions of the 
Champlain epoch would correspond to the history of the Canadian Ice 
Age, as that is presented by Sir William Dawson, who asks only for lo- 
cal glaciers, moderate submergence in the St. Lawrence basin, and an 
Arctic current, to explain all the phenomena which he has observed. 
Hence the advocates respectively of icebergs and of land ice as the chief 
agency of formation of the drift may harmonize their views by conced- 
ing, each to the other, an additional cold epoch. By doubling the Ice 
Age, each side can retain its own pet theory and yet allow its opponent 
the same privilege. 
The occurrence of 55 species of temperate fossil shells in the till of 
drumlins near Boston proves the existence of a mild preglacial climate 
and of an ensuing ice-sheet extensive enough to pile up the largest of 
our grand moraines and drumlins, probably amassing these marginal 
and submarginal drift deposits during the Champlain epoch. 
The Mecklenburgian stage in the Glacial period, as described by Gei- 
kie for Europe, has the following points in common with the Champlain 
epoch in America: first, marine fossiliferous clays, with Arctic mol- 
lusca; second, fluviatile clays, with leaves of Arctic plants; and third, 
the deformations of the earth's crust which have been studied by De 
Geer both in Sweden and North America. If the Mecklenburgian stage 
is necessarily the equivalent of the Wisconsin, the moraines of all the 
northern United States and Canada may l^e referable to the Champlain 
epoch of land depression and consequent departure of the ice-sheet, 
which was represented finally by many local glaciers. 
