BOUNDARY OF THE GLACIATED AREA. 161 



absolutely were. But we will give the facts as they now 

 appear. 



The facts will be best appreciated by somewhat detailed 

 study of the portion of the Allegheny Valley which passes 

 through Warren and McKean counties in Pennsylvania and 

 Cataraugus County in New York. The upper Allegheny 

 descends from the high tableland of Potter and McKean 

 counties in a northerly direction, and consequently was 

 obstructed by the advancing ice, both of the Kansan and of 

 the Wisconsin epochs. Abundant evidence of the slack water 

 thus produced is seen all along this part of the valley, from 

 Coudersport and Keating through Port Allegheny and Turtle 

 Point down to Salamanca in Xew York where the stream 

 turns abruptly to the south. But the evidences of a flooded 

 condition of the valley at the time of the extreme extension 

 of the ice still continues down stream well-nigh to the Ohio 

 River. Everywhere along the course of this valley fans of 

 gravel appear at the level of the glacial high water, wherever 

 tributary streams come in from a higher level. At Warren 

 this fan is 400 feet above the present water level and at Frank- 

 lin, 650 feet. 



In the words of Professor Williams' report, " The affluents 

 of the Allegheny show traces of high water. Those flowing 

 from the glacier are generally aggraded and reversed: those 

 from the Pennsylvania highlands are also aggraded but with 

 local material. The narrowness of their valleys allowed the 

 removement of sediment when the water level brought the 

 bottoms within the area of scour, and it is only in favored 

 places that the evidences remain. Some, however, as Red 

 Bank Creek, and the Kiskiminetas-Conemaugh system show 

 abundant traces of deep sedimentation. . . . At times 

 the conjunction of sudden bends in the main stream and the 

 debouchment of short side valleys which branch from the same 

 area have caused eddies or deflections of the main stream and 

 have aggraded the side vallej's so as to resemble portions 

 of a river channel at elevations higher than the present one." 



