Geology and Topography of Western New York. 95 
Hudson ; forming for itself a channel through the Highlands, if 
that pede. did not previously exist. 
The large quantity of primitive boulders seatterdd over the sur- 
face, and distributed promiscuously through the diluvium, would 
seem to indicate some such movement. ‘That they came from 
the north, has ‘often been suggested ; and the fact, that the near- 
est primitive rocks, in place, occur in that direction, renders the 
assumption highly probable. I have noticed one within the 
boundaries of this city, containing the Labradorite: It is doubt- 
less identical with the Hypersthene rock in Essex county,* or 
with a similar rock described by Dr. Bigsby, as occurring on the 
northeast coast of Lake Huron,+ and probably ‘came from one of 
those locations. 'That loose masses of rock have been frozen into 
cakes of ice, and widely distributed over the surface of the earth, 
seems to admit of no doubt, as-the same phenomenon may be 
witnessed in all currents of the ocean which flow from = lati- 
tudes towards the equator. 
But by whatever agent these boulders have been transported, 
whether by the buoyancy of congealed water, and dropped in a 
more southern latitude, when disencumbered of their icy bark, or, 
swept along by the unaided force-of currents, tides and waves, 
they have left their. “ marks” engraven on the surface of the 
limestone rocks, in characters which bid fair to prove indelible, 
and by which we may obtain a clew to their early history. 
‘The Niagara river takes a course at right angles to the general 
direction of Lake Erie, and, in its descent to Lake Ontario, cuts 
directly across the limestone terrace, which, at this point, exceeds - 
thirty miles in breadth. The upper strata of this lime-rock, con~ 
tain layers and strings of chert, which form a kind of net-work, 
and render them almost incapable of disintegration from ordinary 
causes. These strata form both the barrier at the outlet of Lake 
Erie, and the rapids, between Buffalo and Black Rock. Below 
the northern outcrop of these cherty layers,.which may be re-. 
garded as forming a kindof step‘on the terrace, and upon those 
strata which terminate at the mountain ridge, lie the shallow val- 
leys of the -Tonnewanda and Chippewa creeks, one of which 
flows to the west,-and the other to the east; both pacing the 
— between Black Rock and the Falls. 
Borner 
“a Reports, tg and 1838. 
pience, Vol. vii. p. 69. 
* ~-# See New York Geol 
+ American Journal ot 
