Geology and Topography of Western New Yor'k. 101 



Wherever the strata come in sight on the island, they conform 

 to those in the bed of the rapids, and are equally water-worn and 

 denuded. A portion of rock, recently uncovered by the en- 

 croachment of the rapids upon the west bank of the island, pre- 

 sents the same features, and can only be distinguished from those 

 which have buffeted the fury of the torrent from time immemo- 

 rial, simply by the knowledge of the naked fact of their recent 

 exposure. One of the principal ledges, also, which extends en- 

 tirely across from the Canada shore, may be traced some distance 

 into the island ; and its water-worn and ragged masses, project- 

 ing above the soil, afford conclusive proof, that the conformation 

 of the bed of the rapids, and the surface of the rock which un- 

 derlies the tertiary on the island, was effected by the same agent 

 and at the same time. 



No rapids could then have existed at this place, for the island 

 has since received a tertiary deposit of clay, horizontally strati- 

 fied, which is overlaid by one of gravel containing fresh water 

 shells. These two deposits, at the lower end of the island, be- 

 tween the cataracts, measure thirty three feet in thickness. I 

 have already mentioned, that this clay resembles the numerous 

 beds in this vicinity ; they all probably belong to the same gene- 

 ral deposit. Mr. Rogers thinks this deposit took place from the 

 waters of a tranquil lake.* The fact, however, of its contain- 

 ing gravel stones and water-worn fragments of the rock on which 

 it rests, (as do all of these beds,) would seem to indicate a dif- 

 ferent origin. I suspect this clayey deposit may have been 

 brought on by the overflowing of tides, after the rocky bed had 

 become so much elevated as to be protected from the violence of 

 the surge. The surface, where large tracts are overlaid by it, is 

 marked by meandering swales, which strike the observer as fit 

 channels to conduct the water back to its proper level at ebb 

 tide, after having parted with a portion of its sedimentary matter. 

 No proof surely could be more conclusive than these tertiary beds 

 on Goat Island, that the rapids have not receded, — whatever may 

 be the fact in regard to the cataract itself. 



From the Falls to the Whirlpool, a distance of about three 

 miles, I have observed no indications which have a direct bear- 

 ing on the question of recession ; but at this latter place, phe- 



* American Journal, Vol. xxvii, p. 330. 



