NIAGARA FALLS AND VICINITY 75 



which is found Hving in the Niagara river today, but only on the 

 rocks and boulders lying in the constant spray of the modern 

 cataract. 



After passing Foster's fiats, the scene of greatest erosive activity 

 seems to have been transferred to the left bank of the river. This 

 is indicated by the verticality of this side of the gorge south of Fos- 

 ter's flats, which suggests active erosion, while the lowland known 

 as Ongiara park opposite to this on the New York side of the river, 

 with its enormous boulders scattered about, recalls the dry chan- 

 nel on Fosters flats or the foot of the present American fall, and 

 suggests an amount of water insufhcient to remove them. This 

 may be accounted for by assuming that the nearness of the fall had 



Fig. 18 Longitudinal section of the Niagara gorge from the falls F to Queenston hJghts E, show- 

 ing strata of west bank and depth of channel. (After Gilbert) E railway bridges. W whirlpool- 

 Foster = Foster's flats. Figures indicate miles. 



given the river itself greater momentum above the fall, and that 

 hence it dug deeper into the old drift-filled valley of the St Davids 

 at the whirlpool. As a result, the deflection of the current to the 

 right bank became more abrupt, striking the New York bank im- 

 mediately south of where Ongiara park now is, and, being again de- 

 flected toward the Canadian side, it reached this just at the southern 

 end of Foster's flats, thenceforth for a time causing the most active 

 erosion on that side. The washing out of the drift from the old 

 St David's channel furnished the river with tools with which it was 

 able to cut down into its bed, so that in this portion erosion was 

 probably both by backward cutting of the falls and downward cut- 

 ting of the river above the falls. 



We have so far considered the falls as of simple type, but it is 

 by no means certain that such was the case. If we judged from 

 analogy with other streams which have cut gorges in the same strata 

 as those found at Niagara, we should suppose that, as in the case 

 of these streams, a separate fall was caused at Niagara by each re- 

 sistant layer. Thus in the lower Genesee river, at Rochester, one 

 fall is caused by the upper hard bed of the Medina formation, an- 



