SUPERFICIAL DETRITUS. 
321 
quite evident they are of subsequent origin to the great body of detritus. We find similar 
exhibitions too upon the great western prairies, where, for many miles, the difference in eleva¬ 
tion is not more than fifty feet; and here we observe long lines of boulders stretching away 
for miles beyond the reach of vision, as if once forming a line of coast, or deposited along 
some channel or course of a current, though the general surface indicates no influence upon 
this portion beyond what is common to the whole. 
The causes which have given origin to the superficial accumulations, will be noticed under 
different heads. The most universal and uniform in character were evidently produced be¬ 
neath the water of the ocean, or during the elevation of this portion of country.* 
The immense amount of denudation which has taken place in this portion of the State, could 
only have been accomplished beneath the ocean, when it entirely covered the surface of the 
country, and was subject to tides and currents like the present oceans. This view, too, ac¬ 
quires additional support from the fact, that portions of country along the sea shore, which 
have been recently elevated above the water, bear a very close resemblance in many particu¬ 
lars to the more anciently denuded and elevated districts. Along the Massachusetts bay, 
where the high hills of loose materials contain shells of recent marine species, leaving no 
doubt of their modern origin, the surface has all the characters of those sections in western 
New-York covered by drift or diluvium. Extensive tracts often occur, which are almost 
unbroken; while again the surface is broken into irregular hills or ridges, with deep bowl¬ 
shaped depressions, or long valleys, which often communicate in more extensive ones, or 
are enclosed on all sides by drift. The character of large tracts farther south, along the 
Atlantic coast, is extremely similar ; and when we consider the difference in the nature of the 
strata beneath, and the influence of a longer period of weathering, the analogy becomes very 
striking. Thus we may conceive this whole extent of country to have been submerged be¬ 
neath the ocean for a long period ; and that in its subsequent elevation it has been washed by 
the advancing and retiring waves, which have worn the deep indentations in the limestone 
cliffs, and broken up the northern edges of the strata. 
Notwithstanding, however, that this operation would explain many of the phenomena pre¬ 
sented, still there are others which it would leave unexplained. In those portions of the sea 
coast which I have had an opportunity of examining, the inlets and indentations are always 
broad towards the ocean, and narrowing as they recede. In many of our older valleys, how¬ 
ever, we perceive a different form ; the sides are nearly parallel for miles in extent, and they 
do not present the broad or trumpet-shaped mouths which are common to the coast inlets, or 
those in the face of our limestone terraces. 
The valleys of Seneca, Cayuga and Crooked lakes, Canandaigua lake and others, are of 
nearly equal width from one extremity to the other, with nearly perpendicular banks above the 
water. It seems hardly possible that such channels could be excavated by the advancing and 
retiring waves, upon a coast which was gradually emerging from beneath an ocean. 
f This cause has been explained by Mr. Hayes, in an article published in the American Journal of Science, Vol. 35, No. 1. 
[Geol. 4tll DlST.] 41 
