308 THE ICE AGE IN NORTH AMERICA. 



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 Al- 

 legheny at Great Bend, a few miles south of Warren, was 1,170 

 feet. Again, going nearer the head waters of the Allegheny, 

 in the neighborhood of Salamanca, it is found that the ancient 

 floor of the Allegheny is, at Carrollton, seventy 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 neigh- 

 borhood 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. There must, therefore, of necessity 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 toward Lake Erie in this region, direct ex- 

 ploration has not been made absolutely to demonstrate the 

 theories. But, if resorted to, we know, from the facts just 

 stated, that the line of some such drainage valley must be dis- 

 covered. In the opinion of Mr. Carll, Chautauqua Lake did 

 not flow directly to the north, but, passing through a channel 

 nearly coincident with that now occupied by it, joined the 

 northerly flowing stream a few miles northeast from James- 

 town.* It is probable, however, that Chautauqua did not 

 then exist as a lake, since the length of preglacial time would 

 have permitted its outlet to wear a continuous channel of 

 great depth corresponding to that known to have existed in 

 the Conewango and upper Allegheny. 



Farther west as already shown, the Middle Allegheny 

 appears to have followed a channel leading past Meadville 

 through French Creek to the Lake in the vicinity of Erie, 

 Pa., while the drainage of the Monongahela was clearly north- 

 ward through Beaver Creek and the Mahoning and Grand 



* "Second Geological Survey of Pennsylvania," iii. 



