THE PAST AND FUTURE OF NIAGARA. 



567 



of old banks above the Rapids, that even the highest of these ancient 

 banks did not contain a greater river than this which flows through 

 the narrow gorge to-day. 



We assume, then, from all the monuments the river has left of its 

 own history, that the present rate of recession would be a fair measure 

 of the past, except at the Whirlpool and Ferry Landing. Six inches a 

 year, measured on the channel, would place the Falls at Lewiston 

 74,000 years ago. We have no means of knowing how long the quart- 

 zose sandstone, which forms the lowest part of the bank at the Whirl- 

 pool, would have arrested the cataract. This stratum is 25 feet 

 thick, and, as its southward dip is 20 feet a mile, and the slope of 

 the river-channel 15 feet a mile, the Falls would have to cut back 

 through this rock more than half a mile. The halt may have been 

 many thousand years. Add another period for the halt at the landing, 



Fig. 2. 



North. 



South. 



Section or Goat Island. 



No. 6, the Niagara limestone (6 also of Fig. 1); No. 7, the shaly limestone (marked 7 in Fig. 1). The 

 Eapids have been formed by the erosion of this limestone. D, alluvial drift covering the eroded lime- 

 stone. The section will show how great had been the denudation of the limestone by the river before 

 the drift D accumulated, and before the river had found its present level. 



and the age of the channel, from Lewiston to the Horseshoe, may not 

 fall below 200,000 years. Unquestionably the channel has been ex- 

 cavated since the close of the glacial epoch, which science has well- 

 nigh demonstrated occurred about 200,000 years ago. But this chan- 

 nel is only the last chapter in the history of Niagara. 



Standing by the Whirlpool on the east, and looking over the river, 

 we see a break in the ledges of rock which everywhere else form the 

 bank. On the western side, around the bend of the Whirlpool, for a 

 distance of 500 feet, bowlders and gravel take the place of ledges 

 of rock. Many of these bowlders are granite and greenstone and 

 gneiss, which have travelled hundreds of miles from the northeast. 

 This mass of northern drift fills an old river-channel, which we can 

 trace from the Whirlpool to the foot of the escarpment at St. David's 

 about two miles and a half. The reader will see by the map (Fig. 4) that 

 this old channel marked 13 lies in a line with the present channel 

 above the Whirlpool. The opening at St. David's is two miles wide. 

 Here the Falls stood " in the beginning," wide, but not deep. They 

 had cut back two miles and a half when the glacial period came, and 

 lakes and rivers, and the great cataract, were buried under a colossal 



