216 G. F. WRIGHT GLACIAL DAM IX THE ALLEGHENY RIVER 



of the rock-bottom of the Allegheny below Irvine has not been definitely 

 determined (see the Warren Folio of the United States Geological Survey 

 by Mr. Charles Butts, page 9). Still there can be no reasonable doubt 



Figure 1. — Map of the Ticiniiy of Warreix, Pennsylvania 



that the preglacial drainage of the upper part of Tionesta Creek was with 

 that of the neighboring portions of the Allegheny to the north through 

 Conewango Creek. 



The southeex Drainage 



The point, however, on which we need light is : What was the southern 

 line of drainage during the earliest stages of the glacial invasion, when 



