NIAGARA FALLS. 
387 
The strata 1, 2, 3, 4, 5, 6, 7 and 8, forming the escarpment at Lewiston as represented in 
the section, are those through which the gorge of the Niagara is excavated ; all that portion 
above the dotted line b, c, d, as well as the depth of the river, being removed for a length of 
seven miles and a width of twelve hundred to two thousand feet. These rocks dip gradually 
to the south, and all below Nos. 6, 7 and 8 disappear beneath the level of the river before 
reaching the falls. 
The limestone which forms the summit of the terrace at Lewiston, and which at its margin 
is not more than twenty feet thick, gradually increases from the addition of higher layers, till 
at the Falls it has acquired a thickness of one hundred and sixty-four feet.* This limestone, 
about one mile south of the Falls, disappears beneatli the surface, and is succeeded by a soft 
marl of a bluish or greenish-grey color. This formation, which is the Onondaga salt group, 
occupies all the level country from two miles south of the Falls, to Black-Rock, a distance 
of fifteen miles by the course of the river. To this succeeds the limestone terrace before 
described, on the north of Lake Erie. 
The Onondaga salt group occupying this great breadth of country, and forming an important 
item in any calculation regarding the future recession of the falls, had never been noticed by 
any one till the publication of the Annual Reports of 1838. In all previous accounts the 
distance from the Falls to Lake Erie was regarded as underlaid by limestone, and the lime¬ 
stone of Black-Rock was represented as resting upon the Niagara limestone. 
The Niagara river, from Lake Erie to its emergence into the low country at Lewiston, 
has excavated a channel through the rocks represented in the section. The current, for 
the first two miles after leaving the lake, is very rapid; after which it flows on more gently, 
the channel gradually widening as far as Grand island, where it divides, the greater quan¬ 
tity of water flowing on the west side of this island. Farther down, the river expands to a 
width of two or three miles, and presents all the appearance of a quiet lake, with small, low 
islands. The descent from Black-Rock to the head of the rapids is only fifteen feet. Ap¬ 
proaching these rapids the river narrows and the current becomes more violent, and, for about 
one mile before reaching the grand cascade, rushes on, with inconceivable velocity, over a 
declivity of fifty-two feet, to the edge of the chasm, where it is precipitated into a gulf one 
hundred and sixty feet below.t 
The gorge through which the Niagara river now flows presents almost perpendicular walls, 
with a talus at the bottom, formed by the falling of some of the higher strata. The outlet of 
this chasm is scarcely wider than elsewhere along its course. In some places the channel is 
less than two hundred yards across, and again is expanded to twice that width. The breadth 
# Eighty feet only are visible at the Falls; its whole thickness was ascertained by levelling to Porter’s quarry, a mile east of 
the river. 
t The birdseye view, facing page 383, conveys a very good impression of the face of the countiy, and the course of the river from 
Lake Erie to Lewiston. A representation of the course of the river by this method was given by Mr. Robert Bakewell, jr., and 
published in Loudon’s Magazine of Natural History for March, 1830. This one was constructed without having Mr. Bakewell’s 
view before me, and the artist finished his work without seeing it. The idea of thus representing it was doubtless original with 
Mr. Bakewell; but the same mode, to a certain extent, was adopted by Father Hennepin in his sketch which is given in this 
chapter. 
49 
