42 NEW YORK STATE MUSEUM 



ning northward at a rate proportional to the dip of the beds. The 

 ultimate result of all this erosion was the reduction of the land to a 

 low peneplain, which did not rise much above the sealevel. Por- 

 tions of this peneplain are today preserved in a scarcely altered con- 

 dition, in the Niagara upland, the region about Buffalo and other 

 localities. The slight change which these regions have subse- 

 quently undergone leads to the supposition that the peneplain was 

 completed in comparatively recent geologic time, possibly at the 

 beginning of the Tertiary era, or even more recently. This is also 

 shown by the comparative narrowness of the valleys cut into the 

 peneplain surface in preglacial times. The present altitude of this 

 peneplain in the vicinity of the Niagara river is approximately 600 

 feet above sealevel, while southward it rises. There is however 

 good presumptive evidence, some of which will be detailed later, 

 that, during a period preceding the glacial epoch, the land in the 

 north stood much higher than at present, so that the slope of the 

 surface was southward. An accentuation of slope would cause a 

 rejuvenation of the consequent streams, which, in the later stages 

 of peneplanation, had practically ceased their work of erosion on ac- 

 count of the low gradient of the land. As a result of the renewal 

 of erosive activity the early Mesozoic topography was in a large 

 measure restored, but the inface of the Niagara cuesta, the top of 

 which is now found in the Niagara escarpment, occupied in the re- 

 stored topography a position considerably farther to the south than 

 that characteristic of early Mesozoic time. 



We may now examine more in detail the channels of the conse- 

 quent streams which dissected this ancient coastal plain, and the ex- 

 tent of the inner lowlands drained by the subsequent streams tribu- 

 tary to them. 



Dundas valley. The Dundas valley appears to have been the out- 

 let for the master consequent stream of this region, the Dundas 

 river. This valley, as before noted, breaches the escarpment at 

 Hamilton (Ont.), near the extreme western end of Lake Ontario. 

 The valley has been carefully described by Spencer, who considered 

 it the pathway of the preglacial outlet of Lake Erie into Lake On- 

 tario, the drainage of the Erie valley being in his opinion by a 



