THE NIAGARA GULF. 109 



2. In Metamorphic and Silurian Rocks and newer Sandstones. 



1. Gulf between Lake Ontario and Niagara Falls. — These falls are at present six 

 and a half miles from Lake Ontario, at Lewiston : and the whole distance the 

 river runs in a gulf, which at the falls is 160 feet, and at Lewiston, 300 feet 

 deep, and generally about twice as wide at the top as at the bottom. The rocks 

 passed through by the receding falls are the Medina sandstone, the Clinton group 

 of limestone and shale, and the Niagara limestone and shale. All these rocks, 

 except the Niagara group, having a slight southerly dip, have disappeared beneath 

 the bed of the river, and the falls are now in the Niagara group entirely, the shale 

 lying beneath the limestone. 



At the Whirlpool, a little more than three miles below the falls, on the. west 

 bank of the river, the continuity of the rock forming the bank is interrupted by a 

 deep ravine filled with drift materials. This ravine may be traced two miles in a 

 northwest direction, and from thence another depression can be followed to Ontario, 

 at St. Davids, four miles west of Queenston. 



It appears probable, as Professor James Hall has shown in his Report on the 

 fourth District of New York, p. 389, that this ancient ravine may have been 

 formed by oceanic rather than fluviatile action. For its opening on the lake at St. 

 Davids is two miles wide : while that of Niagara river is about a third of one mile. 

 And width of opening is one of the peculiarities of oceanic action, when it forms 

 indentations along a coast, save in the case of purgatories, which are dependent 

 upon a peculiar structure of the rocks. Although, therefore, it be not certain that 

 Niagara river, or the river on a former continent that corresponded to the present 

 Niagara, emptied into Ontario through this ancient ravine, yet since the ravine 

 can be traced no further than the present river, this probably was the lowest part 

 of the country between the falls and Ontario, and not improbably, therefore, the 

 water of lake Erie would find this outlet into Ontario. It is clear, however, that 

 the present channel of the river from Ontario to the falls, has been excavated 

 since the drift period. For when the ravine to St. Davids was blocked up by drift 

 materials, the stream would be forced to find its present rocky channel. Even 

 though the drift rose only a foot higher than the rocks, it would as effectually force 

 the waters over the rocks as if it formed a mountain. Could the river have once 

 surmounted the drift, its work would have been comparatively easy in wearing out 

 a bed through the old ravine. But till it was able to flow over the barrier, it would 

 have no power over it, and must commence its slow work of wearing away the 

 solid rock. The present gulf shows us what it has done since the drift period. 



The above case, as well as the three following examples, are treated in much 

 greater detail; and with much ability, by Professor James Hall, in his Report on 

 the fourth District of New York. 



2. Qulf of Genesee River between Rochester and Lake Ontario. — The Genesee 

 river is remarkable for the striking examples of erosion which it exhibits. Begin- 

 ning at its mouth, on the south shore of Ontario, we find three cataracts between 

 that point and Rochester, which is about seven miles. Three distinct groups of 



