554< Geological Society : Mr. D. Sharpe on the 



whether they could be detected below the present Falls. On the 

 south-west side, in a cliff 12 feet in perpendicular height, a bed of 

 gravel, 7 feet from the surface, contains eight species of fluviatile 

 and one of terrestrial shells, determined for the author by Dr. 

 Gould of Boston, the whole of the former now living in the wa- 

 ters of the Niagara, and some of them even in the rapids. At the 

 south-west extremity of Goat Island this deposit must be 24 feet 

 thick, and it rests on the Niagara limestone. On the right bank 

 of the river, opposite the island, are two river-terraces, one 12 feet 

 above the stream, and the other 12 feet higher; and both have 

 been cut out of this freshwater formation. In making a mill-dam 

 some years ago, the same species of shells as those on Goat Island 

 were thrown out, and Mr. Lyell had still an opportunity of col- 

 lecting them. He was also shown a tooth of the "Mastodon Ameri- 

 canus," which, with another tooth and a bone of the same animal, 

 were discovered in the deposit 13 feet from the surface. From in- 

 formation given to the author by Mr. Hooker, the guide, the forma- 

 tion was found half a mile farther down the river, at the summit of 

 the lofty precipice, 6 feet deep and composed chiefly of gravel. It 

 contained in abundance Cyclas rhomboidea, Valvata tricarinata and 

 Planorbis parvus. This patch of gravel demonstrates, therefore, the 

 former position of the river at a level corresponding to that of the 

 present summit of the cataract, and half a mile below the existing 

 Falls. It proves however, Mr. Lyell says, much more ; for in order 

 that such a fluviatile deposit should have been accumulated in water 

 tranquil enough to allow those shells to exist, there must have been 

 a barrier farther down ; and he is of opinion it may be safely placed 

 as low as the Whirlpool, or three miles from the present Falls. If 

 this be admitted, then, the author says, " we may be prepared to 

 concede that the still narrower ravine beyond the Whirlpool was 

 excavated 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 



