Geology and Topography of Westeim Neto Yoi^k. 99 



qnenoe of the contraction of the channel. This wave terminates 

 abruptly on the inland side, because the quantity of water con- 

 tained in it is so great, and its motion so rapid, that time is not 

 allowed for the surface of the river to be immediately raised by 

 means of transmitted pressure. A tide-wave thus rendered ab- 

 rupt, has a close analogy, observes Mr. Whewell, to the waves 

 which curl over and break on a shelving shore." This phenom- 

 enon takes place in the river Severn, which enters the Bristol 

 channel, where the Bore, during spring tide, is sometimes nine 

 feet high, and rushes up the channel with extraordinary rapidity.* 

 It also occurs in the Ganges, the Burrampoot^r, and the Hoogly 

 rivers ; sweeping off herds of cattle, or whatever else may be 

 overtaken in its course, and occasions more or less interruption to 

 the safe navigation of all these streams.f 



At any rate, the tide in the vicinity of the Niagara must have 

 been very considerable ; and its power, combined with the dash- 

 ing of the waves, seems to be the only rational cause which can 

 be assigned for the excavation of the numerous ravines already 

 noticed. In a paper by Mr. James Geddes, read before the Al- 

 bany Institute,! the fact, that they owe their origin to other than 

 existing causes, is clearly established. 



When the elevation had so far advanced as to confine the 

 current exclusively to the valley of the Niagara, and the chan- 

 nel below the present falls sufficiently deepened to receive and 

 confine the tidal wave within its rocky walls, a power w^as 

 brought into active operation which it is difficult fully to con- 

 ceive without witnessing its eflfects on some of the iron-bound 

 coasts of this continent. The basin of Mines, and its vicinity, 

 at the head of the Bay of Fundy, would probably be a fit place 

 to study the effect of causes which were once active here. 



When we contemplate these powerful agents, which, in every 

 country, have had so much to do in shaping the surface of the 

 earth, and consider, that in the natural order of events they must 

 have been active here ; when we find the proofs of their visita- 

 tion engraven in characters as enduring as the continent itself, 

 we can hardly doubt that they played an important part in exca- 

 vating the deep channel below the falls. And when we contem- 



* Lyell's Geology, Vol, i, p. 274. 



t Rennell, see Philosophical Transactions of the Royal Society, 178|. 



I See American Journal, Vol. ii,p. 213. 



