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this be admitted, then, the author says, ‘“‘we may be prepared to 
concede that the still narrower ravine beyond the Whirlpool was 
excayated by the river cutting back its course.” 
A similar terrace, consisting of the Goat Island deposit, is di- 
stinctly seen also on the Canada side, and at about the same level 
between the Falls and the Whirlpool; but its extent, height and 
fossil contents have not been investigated. 
If, Mr. Lyell observes, the river continue to intersect its way 
back, the sediment now depositing in its bed, above the Falls, will 
be laid dry in places, and cut into in the same manner as the Goat 
Island deposit. 
Assuming that the cataract was once at the Queenstown escarp- 
ment, allowance must be made, in speculating on the probable 
time which has elapsed in cutting the ravine, for a very different 
rate of retrocession at different periods, dependent on the changes 
in the formation intersected, especially of those which successively 
constituted the base of the precipice. At Queenstown and Lewis- 
town the fundamental rock, at the period when the Falls were there, 
was a soft red marl, and the river acted upon the same deposit for 
about three miles, where the rise in the channel, combined with the 
dip of the strata, caused the superincumbent hard quartzose beds, 
23 feet thick, to form the base of the precipice. From this point the 
retrocession must have proceeded much more slowly for about a mile, 
or to the Whirlpool, where a small fall of 6 or 8 feet still marks the 
place of the highest beds of the sandstone. After, Mr. Lyell says, 
the cataract had remained nearly stationary for ages at this point, it 
next receded more rapidly for two miles, having soft red marl 70 feet 
thick to erode its way through; but beds of greater solidity, con- 
sisting of grey and mottled sandstone and Protean limestone, amount- 
ing in all to 30 or 40 feet, then offered a greater resistance, and con- 
tinued to retard the backward movements of the Falls, the Protean 
limestone occurring at the base of the present precipice. 
Lastly, the author offers some observations respecting the future 
retrocession of the Falls, quoting the opinions entertained by 
Mr. J. Hall (Report for 1838) on the effects which the strata 
above the existing cataract will have on the progress of the river, 
and pointing out results similar to those given by Mr. De la Beche 
in his ‘ Manual of Geology.’ But all predictions, Mr. Lyell says, 
regarding the future history of the Falls may be falsified by the 
disturbing agency of man. Already a small portion of the waters 
of Lake Erie is carried off to supply the Welland canal, and another 
canal on the American side of Niagara; and numerous mill-races 
have been projected and others will be required along both sides of 
the river, as the population and wealth of the country increase. 
Many cities also, situated to the eastward of the great escarpment 
and at a lower level, may in aftertimes borrow water from Lake 
Erie, especially as the continued felling of the forests causes streams 
which were formerly constant to become dry in summer; and it 
must not be forgotten that Lake Michigan has lately been made by 
a cutting to feed the Illinois river, and that whatever quantity of 
