INTRODUCTION. 



FOR many years the abandoned water courses in Ohio have 

 perplexed geologists. Most of them are attributed 

 to streams in the immediate vicinity. Some, how- 

 ever, are in such situation that no existing river or creek 

 could produce them unless very great alterations of level 

 should take place. Others interlock in a manner which 

 would require . exceedingly rapid and violent changes in 

 any stream now found within many miles, if their origin 

 is to be thus explained. For example, each one of four 

 ancient valleys located within the limits of Hamilton county, 

 namely, back of Cincinnati, along Mill creek, at North 

 Bend, and across the northern and western ends of the 

 county, is accounted for by assuming that "the Miami river must 

 have once followed this course." But it would be impossible 

 for the Miami to excavate them, because all have a greater 

 depth than the bed of the Ohio river; and the latter could never 

 have been deeper than it is now, for below the mouth of Mill 

 creek there is rock bottom. Besides, the Miami could form 

 them only by accomplishing the improbable feat of eroding 

 a deep channel and then, without any discoverable reason, de- 

 serting this course and carving a new one for itself through the 

 bordering hills. 



The same difficulty is encountered when the attempt is made 

 to connect former and recent stream beds in various other parts 

 of the State. 



The great variation in width of different portions of the 

 Ohio valley has also awaited explanation. A traveler from Pitts- 

 burg to Evansville will find the hills on either side alternately 

 approaching the water and receding from it. In some parts they 

 are so steep and come so near together, as to form a veritable 

 gorge; again, level or terraced bottom lands a mile or even 

 more in width intervene between the shores and the high larids. 

 Moreover, there is no system or regularity about these changes. 

 Sometimes there may be observed a gradual increase in width, 



