at part of the chasm,
which has been the work of the last hundred and fifty years resembles
precisely, in depth, width, and character, the rest of the gorge which
extends seven miles below, it is most natural to infer, that the entire
ravine has been hollowed out in the same manner, by the recession of the
cataract.

It must at least be conceded, that the river supplies an adequate cause
for executing the whole task thus assigned to it, provided we grant
sufficient time for its completion. As this part of the country was a
wilderness till near the end of the last century, we can obtain no
accurate data for estimating the exact rate at which the cataract has
been receding. Mr. Bakewell, son of the eminent geologist of that name,
who visited the Niagara in 1829, made the first attempt to calculate
from the observations of one who had lived forty years at the Falls, and
who had been the first settler there, that the cataract had during that
period gone back about a yard annually. But after the most careful
inquiries which I was able to make, during my visit to the spot in
1841-2, I came to the conclusion that the average of one foot a year
would be a much more probable conjecture. In that case, it would have
required thirty-five thousand years for the retreat of the Falls, from
the escarpment of Queenstown to their present site. It seems by no means
improbable that such a result would be no exaggeration of the truth,
although we cannot assume that the retrograde movement has been uniform.
An examination of the geological structure of the district, as laid open
in the ravine, shows that at every step in the process of excavation,
the height of the precipice, the hardness of the materials at its base,
and the quantity of fallen matter to be removed, must have varied. At
some points it may have receded much faster than at present, but in
general its progress was probably slower, because the cataract, when it
began to recede, must have had nearly twice its present height.

From observations made by me in 1841, when I had the advantage of being
accompanied by Mr. Hall, state geologist of New York, and in 1842, when
I re-examined the Niagara district, I obtained geological evidence of
the former existence of an old river-bed, which, I have no doubt,
indicates the original channel through which the waters once flowed from
the Falls to Queenstown, at the height of nearly three hundred feet
above the bottom of the present gorge. T