nd the cliff
the spell is broken; for we scarcely recede a few paces, before the
ravine and river disappear, and we stand on the black and rugged surface
of a vast current of lava, which seems unbroken, and which we can trace
up nearly to the distant summit of that majestic cone which Pindar
called "the pillar of heaven," and which still continues to send forth a
fleecy wreath of vapor, reminding us that its fires are not extinct, and
that it may again give out a rocky stream, wherein other scenes like
that now described may present themselves to future observers.

[Illustration: Fig. 17. Lake Erie. The Falls.

Limestone Shale.

Lewiston. Niagara River. Queenstown.]

_Falls of Niagara._--The falls of Niagara afford a magnificent example
of the progressive excavation of a deep valley in solid rock. That river
flows over a flat table-land, in a depression of which Lake Erie is
situated. Where it issues from the lake, it is nearly a mile in width,
and 330 feet above Lake Ontario, which is about 30 miles distant. For
the first fifteen miles below Lake Erie the surrounding country,
comprising Upper Canada on the west, and the state of New York on the
east, is almost on a level with its banks, and nowhere more than thirty
or forty feet above them.[282] (See fig. 17.) The river being
occasionally interspersed with low wooded islands, and having sometimes
a width of three miles, glides along at first with a clear, smooth, and
tranquil current, falling only fifteen feet in as many miles, and in
this part of its course resembling an arm of Lake Erie. But its
character is afterwards entirely changed, on approaching the Rapids,
where it begins to rush and foam over a rocky and uneven limestone
bottom, for the space of nearly a mile, till at length it is thrown down
perpendicularly 165 feet at the Falls. Here the river is divided into
two sheets of water by an island, the largest cataract being more than a
third of a mile broad, the smaller one having a breadth of six hundred
feet. When the water has precipitated itself into an unfathomable pool,
it rushes with great velocity down the sloping bottom of a narrow chasm,
for a distance of seven miles. This ravine varies from 200 to 400 yards
in width from cliff to cliff; contrasting, therefore, strongly in its
breadth with that of the river above. Its depth is from 200 to 300 feet,
and it intersects for about seven miles the table-land before described,
which terminates suddenly at