he river bends; the
Horseshoe immediately accommodates itself to the bending, and will
follow implicitly the direction of the deepest water in the upper
stream. The flexures of the gorge are determined by those of the
river channel above it. Were the Niagara centre above the fall
sinuous, the gorge would obediently follow its sinuosities. Once
suggested, no doubt geographers will be able to point out many
examples of this action. The Zambesi is thought to present a great
difficulty to the erosion theory, because of the sinuosity of the
chasm below the Victoria Falls. But, assuming the basalt to be of
tolerably uniform texture, had the river been examined before the
formation of this sinuous channel, the present zigzag course of the
gorge below the fall could, I am persuaded, have been predicted, while
the sounding of the present river would enable us to predict the
course to be pursued by the erosion in the future.

But not only has the Niagara River cut the gorge; it has carried away
the chips of its own workshop. The shale, being probably crumbled, is
easily carried away. But at the base of the fall we find the huge
boulders already described, and by some means or other these are
removed down the river. The ice which fills the gorge in winter, and
which grapples with the boulders, has been regarded as the
transporting agent. Probably it is so to some extent. But erosion
acts without ceasing on the abutting points of the boulders, thus
withdrawing their support and urging them gradually down the river.
Solution also does its portion of the work. That solid matter is
carried down is proved by the difference of depth between the Niagara
River and Lake Ontario, where the river enters it. The depth falls
from 72 feet to 20 feet, in consequence of the deposition of solid
matter caused by the diminished motion of the river. [Footnote: Near
the mouth of the gorge at Queenston, the depth, according to the
Admiralty Chart, is 180 feet; well within the gorge it is 132 feet.]

The annexed highly instructive map has been reduced from one published
in Mr. Hall's 'Geology of New York.' It is based on surveys executed
in 1842, by Messrs. Gibson and Evershed. The ragged edge of the
American Fall north of Goat Island marks the amount of erosion which
it has been able to accomplish, while the Horseshoe Fall was cutting
its way southward across the end of Goat Island to its present
position. The American Fall is 168 feet