1N2 The American Geologist. March, 1894 
river far below the present lake surface; the tributary rivers 
occupied nearly the same valleys as now, but at greater 
depths, and the valley sides were uneven mountain slopes, un- 
marked by level plains and terraces. 
The Glaeial period requires little comment. The entire re- 
gion shows abundant evidence that it was covered by the ice, 
but below the high level terraces the till and striated ledges 
are largely concealed by the later deposits. 
The (Jhamplain Glacial Lake. Though the facts reported 
from the valley of the Red River of the North and from the ba- 
sins of the great Laurentian lakes made it appear probable 
that this valley contained a glacial lake while the ice was re- 
treating down it. I did not, at first, find direct evidence of 
this, but am now convinced that such a lake did exist. 
Prof. J. E. Todd has briefly stated the reasons for the ob- 
scurity of shore lines of glacial lakes.* To apply them to 
theChamplain valley two others must be added: 1. Whatever ; 
effects the glacial lake may have left, below the later marine 
limit, are concealed by the heavy marine deposits; 2. The 
mountains on either side of the valley were probably some- 
what independent centers of ice dispersion, even so late as 
when the ice-sheet had retreated beyond the St. Lawrence and 
the sea had been admitted. At any rate, the tributary streams 
coming from those mountains seem to have been much flooded 
at that time. It is necessary, in order to account for the 
heavy marine accumulations, to suppose either that it was a 
period of extensive Hoods, or that the marine conditions were 
of long duration. The effect of the floods upon the already 
scanty deposits of the glacial lake would be to largely re- 
move wdiat evidence had been left above the marine limit. 
On either side of the valley, at least as far north as to 
Plattsburgh, strong terraces exist up to a certain hight, which, 
from their relations to the clay, seem to mark the marine 
limit, while above that level faint traces of terrace action can 
be found to one or two hundred feet higher. These faint ter- 
races never show marine shells; they are usually of glaciated 
pebbles and cut directly from the till. These levels seldom 
or never appear in harder materials than till. They were of 
short duration. 
*Am. Geologist, vol. x, p. 299, Nov., 1892. 
