1872.] ue [Perry. 
_ js it in any respect inconsistent; inconsistent in itself considered; in- 
consistent with well-recognized principles generally; inconsistent 
with the little we know of the record in its details, as it lies spread 
out for inspection in New Eneland? Simply because the iceberg 
theory appears untenable it does not follow that the glacier hypothe- 
sis is true. The fact that able men have adopted the latter view may 
be, indeed it is, in so far a presumption in its favor. But men of 
real ability have sometimes advocated indefensible positions. The 
matter, therefore, needs to be examined; it should be critically dis- 
cussed in all its aspects; ventilated that, if it be true, it may be kept 
fresh, and made more widely prevalent in its influence; shaken up 
that we may see it in its more prominent and important bearings, 
and receive it or reject it, according to the clear indications furnished 
by a discussion of the facts in question. Every one who would master 
the subject should look at the evidence, and judge of it for himself, 
in the best and broadest light at his command. 
But such an examination of facts and discussion of evidence can- 
not be completed ina moment. It is needful to go over the whole 
sround cursorily, and look at some of the more salient aspects of the 
subject from various points of view. As this is the explanation which 
Prof. Dana advocates,—which, indeed, he seems to recognize more 
broadly in the paper before us than in any of his previous writings,— 
it will be well to notice particularly how far he is in consonance or at 
discord with the glacier hypothesis as properly looked at, and with 
the facts requiring an interpretation. With a view to the fairest ex- 
hibition of his positions we may go on the supposition that they are 
true, putting them meanwhile to the test of what is found in the field, 
and thus passing in review some of the more prominent relations of 
the subject. With this aim we propose to take up the consideration 
of a position which he advocates, in his explanation of the supposed 
glaciation of the country, viz.,— 
§4. The Elevation of the Land. 
In order to account for the intense cold which apparently prevailed 
during the drift period, Sir Charles Lyell has conjectured that there 
was a variation in the level of the land-masses of the earth; he also 
adds that a great uplift in the boreal part of the Arctic hemisphere 
would have induced a marked change in the climate. ‘This conjec- 
ture has naturally led to the supposition that there were high moun- 
