A CLOCK OF RECENT GEOLOGICAL TIME 359 



brink of the gorge, and Fosters Flats to a lower plain near the level 

 of the river (see Fig. 381, p. 355). The peculiar topographic fea- 

 tures at this locality are well brought out in Gilbert's bird's-eye 

 view of the locality (Fig. 385) ; in fact, in some respects better 

 than they -appear to the tourist upon the ground, for the reason 

 that the abandoned channel and the Flats on the site of the since 

 undermined island are both heavily forested and so not easy to 

 include in a single view.. For one who has studied the existing 

 cataract this early monument is full of meaning. Standing, as 

 one may, upon the very brink of the former cataract, it is easy 

 to call up in imagination the grandeur of the earlier surroundings 

 and to hear the thunder of the falling water. A particularly vivid 

 touch is added when, in digging over the sand about the great 

 blocks of fallen limestone underneath the brink, one comes upon 

 the shells of an animal still living in the Niagara River, though only 

 in the continual spray beneath the cataract. 



The Whirlpool Basin excavated from the St. Davids Gorge. 

 It has already been pointed out that a rock channel now filled with 

 glacial deposits extends from the Whirlpool Basin to the edge of 

 the escarpment at St. Davids (Fig. 389, p. 363). In plan this 

 buried gorge has a trumpet form, being more than two miles wide 

 at its mouth and narrowing to the width of the upper gorge before 

 it has reached the Whirlpool. Near the Whirlpool it has been in 

 part excavated by Bowman Creek, thus revealing walls that are 

 well glaciated. Different opinions have been expressed concerning 

 the origin of this channel, one being that it is the course either of 

 a preglacial river or one incised between consecutive glacial in- 

 vasions ; and another that it is a cataract gorge drilled out between 

 glacial invasions after the manner of the later Niagara gorge. In 

 either case its contours have been much modified by the later 

 glacier or glaciers, whose work of planing, polishing, and widening 

 is revealed in the exposed surfaces ; and it is not improbable that 

 a cataract has receded along the course of an earlier river valley. 



As we shall see, there are facts which point rather clearly to an 

 earlier cataract which ended its life immediately above the present 

 Whirlpool. When the later Niagara cataract had receded to near 

 the upper end of the Cove section, or near the present Whirlpool, 

 the falling water must have been separated from this older channel 

 and its filling of till deposits by only a thin wall of rock, and this 



