56 BULLETIN OF THE LABORATORIES 



unknown depth, and presents a great level drift plain. Rock 

 is not exposed at any point along this line. At London, L, 

 the drift is at least 250 feet deep, making the rock floor there 

 about 700 feet A. T. ; at Urbana about 870 feet A. T. 



The great valley of the Mad river at Urbana has been described 

 by Prof. Moses^ as a great basin. It is apparently rock bound on 

 the south and north and drift bound east and west. The drift to 

 the west is piled up to a great depth, being probably the deepest 

 drift in the world. A gas well at St. Paris, Champaign County, 

 penetrated 530 feet of drift. ^ This did not reveal the rock floor 

 so that it is not known how much deeper the filling extends but 

 this would show that it is certainly not more than 650 feet 

 A. T. or 210 feet above the Ohio at Cincinnati while the pres- 

 sent Mad River at Urbana is abont 1000 feet A. T. and has 

 about 560 feet fall to the Ohio. 



Neglecting the drift then, the general rock surface of the 

 country rises towards the south onto the tablelands of 

 Hamilton County to an elevation of about 1000 feet A. T. 

 This would give a fall of at least 350 feet from the tablelands 

 at Cincinnati to the rock floor at St. Paris, thus showing that 

 all the Miami drainage is, like the other rivers of southern Ohio 

 already referred to, up the general slope of the rock surface. 

 This could be accomplished by a gradual rise of the land at the 

 mouth equal to the rate of river erosion or by cutting down the 

 margin of a basin. We have no evidence of such an uplift at this 

 time hence we conclude that it was due to the latter cause. But 

 however that may be, there appears to be no evidence of a val- 

 ley of the size and form and depth required to carry the pre- 

 glacial Muskingum drainage into the Ohio river at any point at 

 or above Cincinnati. 



12. Evidence of a Buried Channel to the North West. 

 Gas wells which penetrate the drift to the west and north- 



^Proceedings of the Central Ohio Scientific Association Vol. I, Pt. i. 

 ^Ohio Geological Survey Vol. VI, Page 276. 



