' 
Perry.] 70 [February 28, 
planation fails we are not necessarily to drop the matter, or even ice- 
agency, but may inquire whether ice seen under a different aspect, 
and in the light suggested by modern glaciers, can furnish an ade- 
quate explanation of the facts in question. 
By the glaciation of the region we are to understand that it has 
undergone an experience in which ice played the most prominent 
part; that the country was once liberally iced over, ice being the 
predominant agency and the characteristic feature of the times; that 
for a while the whole land was covered by an immense sheet, a 
widely-extending expanse of ice of great thickness; and that in con- 
nection with the accumulation, the continuance and the wasting of 
this vast body of frozen water, it underwent all the processes neces- 
sary to the production of the manifold effects everywhere met with, 
and some of which have been enumerated as indicative of ice- 
agency. ‘This is substantially the view which not a few now take of 
the matter, the view which has been presented and discussed with 
great ability by Prof. Agassiz,1 to say nothing of later adherents, as 
Prof. Guyot, Prof. Forbes, Prof. Tyndall, and many other distin- 
guished observers. Whether it will pass the ordeal of a searching 
examination is now the important question. If not able to render 
the facts clearly intelligible, consistent with each other, and with all 
that is known of related facts in nature, we must regard it as so far 
unsatisfactory and undeserving of confidence. In case, however, 
close examination shows that the presence of a vast body of ice 
would afford the vantage ground requisite to a clear and coherent 
understanding of all the main phenomena, we may conclude that 
there is presumptive evidence of the truth of the view, so long as 
nothing adverse comes to light. 
How is it, then, with the glacier hypothesis—the hypothesis of a 
continental ice-sheet, a portion of which is supposed to have spread 
over this region? Does it meet the facts, and bring in such a flood 
of ight as to render them comparatively easy of explanation; easy 
in the sense that there is nothing forced and unnatural about it? Can 
it help us to see them as the legitimate outflow of its agencies? Or 
1Prof. Agassiz was the first, I believe, to apply the glacial theory to the drift 
phenomena not only of the British Isles, but also of this country. Remarks on 
the drift of Lake Superior, made before the American Association for the Ad- 
vancement of Science in 1848, contain, so far as I am aware, the first published 
application of the view to this country—remarks which were more fully expanded 
in his work on Lake Superior, published in 1850. 
