.30 THE PREGLACIAL DRAINAGE OF OHIO. 



adjacent regions it appears that the drainage modifications 

 therein observed were intimately associated with the phenomena 

 of the glacial period. The blocking of the northern discharge of 

 the Monongahela and upper waters of the Ohio by the advancing 

 ice or its extensive deposits turned the waters of the present 

 upper Ohio region over the New ^Martinsville col into this basin. 

 In a similar way the waters of the ^luskingum which originally 

 discharged westward past Newark and into the Scioto were 

 deflected southward over the old col on the north Morgan county 

 line. The conditions in the case of the Hocking are not so 

 clear and at once suggest that there were other factors present 

 besides the simple introduction of these large streams at par- 

 ticular points. For if the waters of the Hocking were set over 

 the Athens col, due to the damming action of the ice or its 

 deposits, on some northward flowing stream, it would seem 

 as though it would have followed down the ]\Iiddle Fork of 

 Shade River branch of the old drainage and would not have 

 crossed the col below the mouth of Federal Creek. As this 

 region is far beyond the direct action of the ice and the only 

 glacial deposits of note are the gravel trains found in the valleys 

 of the Ohio, Muskingum and Hocking it at once becomes evident 

 that the modifications wholly within the region must have been 

 produced in some other way than by the direct action of the ice or 

 its deposits. Such for example are the modifications of the 

 lower Muskingum within Washington county. If the waters 

 w^iich headed at the north Morgan county line col were flowing 

 over the gap south of Roxbury and through the old valley at 

 Layman at the time the Muskingum waters first crossed this col 

 it would seem that the larger stream would have followed the 

 more direct and open line of the old drainage than to have turned 

 to the north over the Meigs Creek col and again over the Lowell 

 col. It seems necessary to assume one of two possible explana- 

 tions. First, that there was some obstruction to the old direct 

 line or that the modifications antedate the introduction of the 

 Muskingum waters and that when the waters came over the 

 col they followed the drainage they discovered already estab- 

 lished, which was practically coincident with the present system. 

 Of these two explanations the last seems best to fit the facts 



