346 ORTMANN— THE ALLEGHENIAN DIVIDE. [April 18, 



This stream piracy or capture must have gone on all through the 

 history of the mountains ; but the evidence for the older cases is 

 largely lost on account of the base level conditions prevailing at vari- 

 ous times. Only more recent (Postcretaceous) cases are more or less 

 clear. But in a general way the present rivers indicate that stream 

 capture has been most effective in the northern parts of the Alle- 

 ghenies, and, toward the south, the various rivers show this phe- 

 nomenon in a lesser degree. (Davis, 1889; Hayes and Campbell, 

 1894, p. 102; also Campbell, 1896.) In addition, these processes 

 were modified by a tilting of the reèlevated peneplain in opposite 

 directions in the north and south (Powell, 1896, p. 79). 



C. Present Condition of Drainage. (See Plate XII.) 



At the present time we have only in the southern Appalachians 

 the remnants of the primitive condition of the drainage, streams 

 running toward the west, with their sources near or in the Blue 

 Ridge, well to the east. This is the case in the Tennessee and New 

 River region. New River is a good example of this, and we may 

 safely regard this river as representing most nearly the original 

 drainage features (Davis, 1907, p. 732: " There is not another river 

 in the whole Appalachian region that so well preserves its ancient 

 course.") 11 



Following the Allegheny Mountains and the Allegheny Valley 

 northward, we meet streams draining more and more in an easterly 

 direction, first the Roanoke, then, in succession, the James, Potomac 

 and Susquehanna, and it is interesting to notice that the first one 



11 Davis means here by " ancient " preeminently the Pretertiary time. 

 But probably the present New River is not the oldest line of discharge out 

 of this region. Using the same methods as used by Davis (1889) for the 

 construction of the old Anthracite River in Pennsylvania, we would obtain 

 an old river running West in the depression between two elevations (monad- 

 nocks), along which now runs the Chesapeake and Ohio Railroad (between 

 Covington and Hinton, see PI. XII. and profile, PI. XIV., fig. 2). Probably the 

 fault on the western side of Peters Mountain also played a part in defining 

 this oldest line of discharge. The present New River would then be a later 

 (but probably also Pretertiary) feature, and would have about the same re- 

 lation to the old river, as the present Susquehanna has to the old Anthracite 

 River, after its reversion. 



