Perry.] 104. [February 28, 
and many more which might be readily adduced, indeed the mani- 
fold other facts of a cognate character, all seem to be just what we 
should presume they would have been, in case the whole region had 
been once traversed by a vast body of ice, impelled, slowly but 
steadily, toward the south, as the winter flow of an ice-continent. 
And this view enables us to understand how the ice, which must 
have been thicker in the deep valleys of the Hudson, of the Connec- 
ticut, and of other north-south streams, than on the intermediate 
hills, would in connection with the main mass move onward beyond 
their present outlets, especially during the Middle Glacial times, and 
form the submarine glaciated channels, as it made its way over the 
shallow plateau to the deep sea. And the same is true in respect to 
various other points, some of which are very hard to interpret on any 
other recognized hypothesis, than that of an extensive mass of ice 
covering the whole region to a great depth. 
§ 14. The Action of the Ice-Sheet, 
(2.)- "4s attested by the overlying material. The traces of this ac- 
tion reveal additional evidence of the time required for the accom- 
plishment of so much work, and of the way in which it was effected. 
Only a few facts need to be mentioned as illustrative and confirma- 
tory of this phase of the subject, and these the most obvious. If 
there were such a denudation of the surface of the country as has 
been already referred to, it must have led to certain results—it could 
not, indeed, fail to reveal itself in given effects—which may be prop- 
erly regarded as accompaniments u glacial agency. 
There would be, in the first place, the erosion of a vast amount of 
material. Something of the kind would necessarily follow, if a 
mountain of ice shod with tough erratics moved slowly but steadily 
along, constantly furrowing the surface of the subjacent solid rocks 
and scraping up and carrying off the loosened material! Under 
these circumstances, we should expect an important work to be done 
during the earlier part of the ice-period. The local glaciers, filling 
the mountain valleys, would, as they advanced, plough up the sur- 
face, and push along, at once before them and beneath, a large 
1Professor Agassiz says, ‘‘ On creeping under a glacier, I actually saw the lower 
surface of the ice studded with pebbles and boulders, immovyably set in the glacier, 
like mounted stones; and once I saw, still in its place, the powder that had been 
ground by the rubbing of these pebbles against the wall rock of the valley,:in 
which the glacier was moving.”’ Similar remarks are of frequent occurence in his 
various works on glaciers. 
