206 MAN AND THE GLACIAL PERIOD. 



to the Glacial period the drainage of the valley of the 

 upper Alleghany north of the neighbourhood of Tidioute, 

 in Warren County, instead of passing southward as now, 

 was collected into one great stream flowing northward 

 through the region of Cassadaga Lake to enter the Lake 

 Erie basin at Dunkirk, N. Y. The evidence is that be- 

 tween Tidioute and Warren the present Alleghany is shal- 

 low, and flows over a rocky basin; but from 'Warren north- 

 ward along the valley of the Conewango, the bottom of 

 the old trough lies at a considerably lower level, and slopes 

 to the north. Borings show that in thirteen miles the 

 slope of the preglacial floor of Conewango Creek to the 

 north is 136 feet. The actual height above tide of the 

 old valley floor at Fentonville, where the Conewango 

 crosses the New York line, is only 964 feet ; while that of 

 the ancient rocky floor of the Alleghany at Great Bend, 

 a few miles south of Warren, was 1,170 feet. Again, 

 going nearer the head- waters of the Alleghany, in the 

 neighbourhood of Salamanca, it is found that the ancient 

 floor of the Alleghany is, at Carrollton, 70 feet lower than 

 the ancient bed of the present stream at Great Bend, 

 about sixty miles to the south ; while at Cole's Spring, in 

 the neighbourhood of Steamburg, Cattaraugus County, 

 N. Y., there has been an accumulation of 315 feet of drift 

 in a preglacial valley whose rocky floor is 155 feet below 

 the ancient rocky floor at Great Bend. L T nless there has 

 been a great change in levels, there must, therefore, have 

 been some other outlet than the present for the waters 

 collecting in the drainage basin to the north of Great 

 Bend.* " 



While there are numerous superficial indications of 

 buried channels running towards Lake Erie in this region, 



* For a criticism of Mr. CarlPs views, see an article on Pleisto- 

 cene Fluvial Planes of Western Pennsylvania, by Mr. Frank Lev- 

 erett, in American Journal of Science, vol. xlii, pp. 200-212. 



