to be liable to be misunderstood. The interesting work of Agassiz, sur 
les Glaciers, showed me how the passage of large masses of ice over the 
surface could produce effects, precisely like those which for twenty five 
years I had been examining with deep interest all over New England. 
No other facts which I had ever seen stated, would show how our strie, 
our transported bowlders, and accumulations of drift, could be explain- 
ed; the flood of light which was thus unexpectedly thrown into my 
path, delighted me; I expressed a warm admiration of the views 
of Agassiz, and used some terms with perhaps too extended a meaning. 
For example, I supposed that the term moraine might designate any ac- 
cumulation of detritus produced by advancing ice, whether glaciers or 
icebergs. Neither when I wrote my Address, nor subsequently, have 
I supposed that the moraines of this country were produced by gla- 
ciers, but always by icebergs; as I endeavored to show, in an extend- 
ed paper on drift, which I read in your presence, before the meet- 
ing of the Association of American Geologists and Naturalists in Bos- 
ton last April. And whatever impression my language may have con- 
veyed, I now declare, that I have never supposed it possible to apply 
the glacier theory of Agassiz to this country without modification. The 
difficulties which I stated in my Address, have always appeared to me 
insuperable against its adoption. 
But it may be said, that I stated in that address, that I felt “con- 
strained to believe its fundamental principles to be founded in truth.” 
Yet in the next sentence I added, ‘* modifications it may require ;” and 
in a note I declared myself satisfied that “ it will need important modi- 
fications ;’ and then, in order to show distinctly what I meant by its 
“ fundamental principles,” and to give the final conclusion at which my 
mind had arrived, I stated my conviction, that “ glacio-aqueous action 
(by which I mean (see note, p. 29; also this Jour. Vol. 41, p. 258) the 
joint action of ice and water, without deciding which has exerted the 
greatest influence) has been the controlling power in producing the phe- 
nomena of drift. Whether the vast currents of water, which must 
have been concerned, were the result of the sudden melting of the thick 
belts of ice around the poles, as Agassiz supposes, or of the elevation 
of the regions around the poles, whereby the ocean was thrown over 
the land, agreeably to the views of De la Beche ; or by the elevation of 
different parts of continents from the ocean, while the greater part of 
those continents were beneath the waters, according to Lyell and Mur- 
chison, I do not feel competent to decide. I rest at present in the po- 
sition, that ice and water were both concerned; and am in doubt wheth- 
er geologists will ever be able to go much farther and remain upon the 
terra firma of logical induction. But to have reached this principle, in 
which I fancy nearly all geologists now agree, seems to me an immense 
advance on this subject; and for this progress in my own mind, I feel 
