Perry.] 1 [February 28, 
tains during the glacial period in the northern portion of this 
continent, and that they were covered with an ice-sheet or abounded 
in glaciers. If we grant that glaciers or an extensive field of ice ac- 
tually thus existed, the question whether there were also such an up- 
lift becomes legitimate, and should be answered accerding to the 
evidence. Now, in his ‘‘Manual of Geology,’’ Prof. Dana suggests 
what has been just pointed out as in part the view of Sir Charles 
Lyell, ‘‘that an elevation of the continent over its northern regions 
of a few thousand feet is sufficient fo account for the existence of a 
glacial epoch in the earth’s later history; and an elevation of five 
thousand feet is as probable as a subsidence of five thousand feet.” 4 
This supposition having been made, he seems tacitly to take for 
granted that there was such an elevation in reality, he assumes the 
thing as a matter of fact. Indeed, in the paper under consideration 
he says that during the glacial period ‘‘the land stood at a higher 
level than now.” ? 
In respect to this supposition, a few remarks may be in place. 
The conjectured elevation referred to took place, as is presumed, at 
the close of the Tertiary era, and was maintained through most of 
the Glacial period, giving rise to a great increase of cold, and to the 
formation of vast fields of ice. Now these suppositions are in no 
way shown to answer to facts; and while it is not easy to establish 
their validity, it is no light task to overthrow them. Indeed, 
whether there were any such preparation for the change of climate 
that probably occurred cannot be readily proved or disproved, any 
more than many other guesses that might be thrown out at hazard. 
These and other cognate conjectures seem to have been made, be- 
cause glaciers were assumed to be impossible without the existence 
of mountain heights. But grant, for the moment, that there was 
such an elevation as the one supposed, it by no means follows, it in 
fact appears hardly possible, that this condition alone would have in- 
duced a degree of cold sufficient for the production of all the phenom- 
ena of the glacial times. Meanwhile I have been unable to find a jot of 
substantial evidence in favor of the implied elevation. Admitting that 
it seems to help us in our explanation of given points, it remains for 
us to see whether these very points may not be equally well explained, 
without reference to this hypothesis. It is no doubt true in 
one aspect of the subject, that an uplifting of the continent to 
1 Manual of Geology, p. 544. 2 Paper cited, p. 48. 
