at 
Address before the Association of American Geologists. 257 
very sudden, why may not the return of the heat have been 
equally sudden? If so, the most powerful debacles must have 
been the result ;* and as the ice would disappear most rapidly 
along its sonshaie border, perhaps in this way a current in that 
direction may have been produced. And yet, I confess that I re- 
gard this theory more defective in not furnishing an adequate cause 
for the southerly course of our drift, than in any other point. 
I find another difficulty in explaining satisfactorily by this the- 
ory, how drift could have been often carried from lower to much 
higher levels; as it has been sometimes if I am not greatly 
mistaken, . Thus, the Silurian rocks of New York, and the 
quartz rock in the valleys of western Massachusetts, have been 
carried over, and left upon, Hoosac and Taconic mountains and 
the Highlands of New York. It is easy to conceive how an im- 
mense sheet of .ice, by its expansive power, should force portions 
of its mass to ascend moderate declivities, of a few hundred feet, 
but not so.easy to imagine them thus forced upwards one thou- 
sand or two csineniownes sashannelonitarighare homi in Newt 
Sry res ote 
_ Another difficulty reuheé.droiesinetaet. that some of Pie most 
remarkable of our moraines are found, not in valleys, but on the 
sea coast, some of them fifty, and others one hundred miles dis- 
tant from any mountains much higher than themselves. — Ir 
to hese. remarkable conical and oblong tanned gaia 
* A curious example illustrative of this point has just been communicated to 
me by Rey. Justin Perkins, American missionary in Persia, not, far from Mt. Ar- 
arat, in a letter dated at Ovoromiah, Nov. 6th, 1840. In giving an account of two 
ve Ww erful earthquakes experienced od oer and around that mountain in the sum- 
: oh . ast accumulation of snow which had been in- 
creasi many centuries, was. 
into pieces, and_parts of it shake 
mense ghia that (it being mi ; 
, and suddenly melting.) torrents of wa’ 
Riiciaainiensia dete mountain, and flooded the plain for some distance around its 
also, the drift has been carried “ from lower to higher 
in the north of wheat n; and he imputes the strie to * icefloes and 
levels,” according to 
d grating upon 
detritus, ‘set = motion the elevation of continental masses, an 
= bottom / fd by the Geological Structure of yer and Central Russia, 
SS &c., by pans and Verneuil, p.13. London, 1341, p- 16. Very soon the Gla- 
cier Theory may need some analogous wisdificanion eeneest aa 
and yet it seems to me that expanding ice:ia'n for moro powerful *gent ree 
tritus up an inclined p. Jane, than currents of water. 
Vol. x11, No. 2 July Sept 1841. 33 
