CAUSES OF CHANGES IN DRAINAGE. 199 



mature. In the discussion of features on the portion of the Ohio between 

 Moundsville and New Martinsville attention was called to evidence that the 

 divide had shifted toward Moundsville because of an advantage held by a 

 drainage line that led southwestward from New Martinsville over one that 

 led northward. It is probable also that the channel which connects Big 

 Bone and Eagle creeks with the Ohio near Warsaw, Ky., became abandoned 

 through piracy, though the precise mode of capture is not yet understood. 

 The changes in drainage just mentioned are of minor consequence 

 compared with changes which were effected by glaciation; but there is a 

 chance that piracy will prove to have been influential in causing changes 

 of great consequence in this region. The diversion of the Middle Ohio or 

 old Kanawha system into the Lower Ohio system seems so remote an event, 

 if we may judge by the work accomplished since it took its present course, 

 that one hesitates to refer it even to the earliest of the several stages of 

 glaciation. But the difficulties of accomplishing this diversion by piracy 

 are perhaps not less than in extending the glaciation far enough back to 

 give time for the work to be done. In discussing this matter, Chamberlin 

 writes: "It would seem to be a rather extraordinary feat of piracy that a 

 river should be able to eat its course back across the Cincinnati arch and 

 drain country in a synclinal beyond, when there were courses of drainage 

 which essentially avoided the arch." The applicability of piracy to this 

 and also to other places in the Ohio drainage system can hardly be decided 

 in the present stage of investigation. 



EARTH MOVEMENTS. 



Earth movement or crust warping may prove to have had influence in 

 causing diversions in the old systems of drainage either by itself or in com- 

 bination with stream piracy. As already suggested, it may have been 

 through these agencies that the old Kanawha was diverted from the Scioto 

 Basin to the Lower Ohio prior to the earliest glaciation. But it is perhaps 

 idle to speculate on this question, since the date of the flexure at the north 

 end of the Scioto Basin is unknown and various other conditions are uncer- 

 tain. Not only here, but elsewhere in the region under discussion, the 

 influence of earth movements upon drainage embraces a broad range of 

 problems which can scarcely be dealt with at present. The possible varia- 

 tions in influence are forcibly illustrated in districts adjoining the one under 

 discussion, and with these illustrations the writer will leave this question. 



