Perry.] 102 [February 28, 
hypothesis of elevation. Indeed, it seems to be rather an incum- 
brance than a help. This being so,it may be asked whether the 
glacial explanation does not greatly impair the force, if it do not en- 
tirely dispose, of the main point urged by Professor Dana, as evi- 
dence of a higher level of land, ae the earlier and middle 
Glacial times. 
But there are not merely traces of erosion; there has been very 
extensive planation of the rocks. This has taken place over a broad 
area, and in a marvellous manner. ‘The surface of the country has 
been rubbed, scoured, and polished to an extent which might be 
deemed incredible, by one who has not studied the subject long and 
carefully in the field. The portion of New England which has not 
been thus planed and smoothed is almost as nothing compared with 
the whole. It comprises, for the most part, only the south-east 
mural faces of hills and peaks, and a few of the highest summits of 
the White Mountains. The parts of the surface thus spared dis- 
tinctly indicate the direction in which the abrading and smoothing 
force acted. The fact that the work of denudation and polishing, 
even on the south-eastern, slopes of hills and mountains, was in all 
cases renewed, after an interval, evinces with equal clearness that 
icebergs were by no means the instruments in operation. It also 
suggests that the sheet of ice, in passing over an elevation, was in 
many instances so arched as to leave a portion of the leeward sur- 
face unaffected, only in due time to resume its suspended work of 
abrasion with renewed force. Indications of such action as this are 
to be found in abundance in various portions of the country. No 
one can need a better exhibition of it than is furnished by the Adi- 
rondacks of New York, whether looked at in outline at a distance, 
or examined in minutest detail. 
There has also been almost equally extensive striation. Nearly 
everywhere the eroded and polished surface has been scored, 
scratched and furrowed. These furrows and scratches and scorings 
vary greatly in size. In rocks recently laid bare they are in some 
cases so fine as scarcely to be discerned by the naked eye; while in 
other instances, they are many inches and even feet in diameter. 
Occasionally the objection has been urged that this striation was not 
produced by the action of sand, gravel, and boulders in the foot of 
the glacier, but is the work of man. In reply it may be said, that 
such markings do not occur merely on surfaces which have been for 
some time bare; on the removal of soil, which evidently had never 
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