y6 NEW YORK STATE MUSEUM 



other by the limestone of the Clinton group, and a third by the 

 Lockport limestone. In the Niagara river we might suppose that 

 at least three, and possibly four, falls had existed at one time. The 

 lowest of these would have been over a hard bed of sandstone,, 

 about 25 feet thick, and about 100 feet below the top of the Medina 

 group. Another might have been caused by the hard capping 

 stratum of Medina sandstone, 10 feet thick. A third over the 30 

 feet of Clinton limestone; while a fourth would have been formed 

 over the Lockport limestone. The second and third would per- 

 haps unite in one, as the shale bed between the two resistant layers- 

 is only 6 feet thick. It may however be objected that in a great 

 cataract the force of the falling water is such as to cause uniform 

 recession of all the layers, and that hence only one great fall existed. 



The whirlpool 



plate 9 



Perhaps the most remarkable part of the entire gorge is its great 

 swollen elbow, the whirlpool. Here the current rushing in from the 

 southeast with great velocity, circles around the basin and finally 

 escapes, by passing under the incoming current, through the com- 

 paratively narrow outlet, in a northeasterly direction. The waters- 

 in the whirlpool have probably a depth of 150 or 200 feet, but 

 both the outlet and the inlet are shallow, for here ledges of the 

 hard quartzose bed of the Medina formation project into the river,, 

 extending in the latter case probably across the channel. An ex- 

 amination of the walls of the whirlpool basin shows that rock is 

 absent on its northwestern side, the wall here being formed of un- 

 consolidated material or drift. This is best seen on descending to 

 the edge of the whirlpool on the Canadian side, through the ravine 

 of Bowmans creek. It will be observed that the Niagara has here 

 exposed a cross-section of the ancient drift-filled channel which ex- 

 tends southeastward from St Davids. This channel appears to have 

 been that of a preglacial stream of the obsequent type, 1 which was 

 tributary to the streams of the Ontario lowland. Some geologists 

 however, notably Mr Taylor, believe that this old channel may have 



^^See chapter 1. 



