oilbeiw.] NIAGARA FALLS. 457 



The continuity of the geologic section in the walls of the canyon is 

 interrupted at one point on the Canadian side. At the locality known 

 as the Whirlpool there is an embayment of the wall, and at the head 

 of that embayment a body of drift is exposed from top to bottom of 

 the bluff, replacing the Paleozoic strata. How much deeper it extends 

 is not known, but the river has here gouged out a deep pool, in which 

 the current is temporarily slackened, and it appears probable that this 

 excavation was in the soft drift. Associated with this feature is an 

 embayment of the Niagara escarpment, near the town of St, Davids. 

 not far away. For the space of a mile the limestone cliff disappears, 

 and is partially replaced by glacial drift. It is believed that this 

 embayment and the preglacial cavity at the Whirlpool constitute parts 

 of the same preglacial valley, a valley opening to the northward and 

 terminating southward within the present river canyon, between the 

 Whirlpool and the cataract. So far as this valley extended the river 

 had an easy task, for its canyon was already dug. 



On the other hand, it is doubted that the river has at all points been 

 able to work as rapidly as now. The height of the Falls is about L60 

 feet (48 m.)j the pool below the cataract has a depth, at the nearest 

 point where sounding has been successful, of 185 feet (56 m.). This 

 great depth of pool appears to be essential to rapidity of recession, for 

 under the American fall there is no pool and there the recession is 

 slow. But the river has a depth comparable with that of the pool for 

 only a mile or two below the cataract, and at most other points the 

 present cross section renders it improbable that a deep pool was ever 

 formed. It is surmised that at such points the rate of recession may 

 have been slow. 



Accordant with this view is the hypothesis, not yet fully tested, that 

 all of the upper lakes, except Lake Erie, once found discharge to the 

 St. Lawrence river by other routes, so that for an unknown traction of 

 postglacial time the Niagara river drained a district only one-eighth as 

 large as that which it now drains. 



The train approaches the Niagara falls from the Canadian side across 

 the suspension bridge, and follows the American bank to the village 

 of Niagara Falls, where it halts for the day. One can conveniently 

 cross again to the Canadian side by the steamer Maid of the Mist, or 

 by the upper suspension bridge, and the geologist will wish to seethe 

 cataract from both sides and from the river brink below, (lout island, 

 which divides the American fall from Horseshoe fall is reached by a 

 bridge from the American shore, and a spiral stairway leads one thence 

 to the water's edge between the two falls. At the head of this stair- 

 way guides and waterproof suits can be secured for a visit to the Cave 

 of the Winds, in which one passes beneath a sheet of falling water con- 

 stituting a portion of the American fall. The path lies partly on talus, 



