THE PREGLACIAL DRAINAGE OF OHIO. 15 



the north Morgan county line and from this col there was a 

 small tributary ran northward into the main preglacial axis. 



The third section is that of the Jonathan Creek which was 

 tributary to this reversed Muskingum section at Zanesville. 

 The headwaters of these northward flowing streams are shown 

 on the accompanying map (Plate I). 



To the east of the region lies the drainage basin of the Mo- 

 nongahela and upper Ohio. The modifications in this section have 

 been very great and have been the object of study by many 

 geologists. A summary of the work done by the earlier stu- 

 dents, with newly added data, is given by Dr. T. C. Cham- 

 berlin and Mr. Frank Leverett in the American Journal of Sci- 

 ence, Volume XLVII, No. 280. According to these authors 

 there was an old col on the Ohio a little below New Martins- 

 ville, W. Va. Fishing Creek being the headwaters of the stream 

 which flowed northward up the present Ohio's course above 

 New Martinsville into the then northward discharging Monon- 

 gahela. The region to the west and southwest remains open 

 to further investigation. 



CHARACTER OF THE BOUNDING WATERSHED. 



The watershed which surrounds the region is a well marked 

 topographic feature and quite regular in its general outlines. 

 It rises to a nearly uniform elevation, being somewhat higher to 

 the southeast and lower to the northwest. To the southeast 

 it forms the divide between the tributaries of the Ohio and the 

 Monongahela. It forms everywhere a high dividing ridge, ex- 

 cept at the several points where it is cut through by the present 

 drainage lines. Here the streams have narrow, gorge-like val- 

 leys and the elevation of the ridge persists surprisingly near to 

 the stream courses. While the cols crossed by the streams 

 must have been low they were evidently quite narrow gaps or 

 else the ridge would show more of a lowering at these points. 

 Only a small portion of the divide is shown on the map and 

 this is cut in but two places, i. e., at the north Morgan county 

 line and below New Martinsville. 



