394 GEOLOGY OF OHIO. 



could be approximately described as the portions of the county that 

 have an elevation of not more than 250 feet above the Ohio River. 



On the other hand, the uplands embrace the lands above this level. A 

 large proportion of them, however, lie at an elevation between 400 and 

 600 feet above the Ohio. This division of the surface of the county is 

 much less definite on the east side of the river than it is on the west, 

 for the reason that the Drift deposits are heavier in the first named 

 district. In other words, the lines of the valleys are here harder to be 

 traced. There are areas of unmistakable uplands, but they are con- 

 nected with the valleys by slopes of considerable extent, which com- 

 pletely obscure the true outlines of the rocky floor. 



The uplands proper are remnants of the Blue Limestone plateau that 

 once occupied all of southwestern Ohio, but so much of which has 

 already been removed by aqueous and glacial denudation. They are 

 almost universally covered with shallow deposits of drift, but over very 

 large areas the character of the underlying rock shows through, giving 

 its peculiar features to the topography, to the agricultural capacity, and 

 to the water-supply of the districts occupied. These upland drift de- 

 posits are in considerable part derived from the waste of blue limestone 

 land to the northward, so that a closer bond of connection exists between 

 the soil and the underlying rock than is usually found in drift-covered 

 regions. A more detailed description of the drift deposits of the county 

 can appropriately find place here. 



DRIFT BEDS. 



The divisions of the drift that have been recognized in those portions 

 of the Third Geological District already reported upon, are found here 

 also. The lowest of these deposits, or that which rests directly upon the 

 bedded rocks, is the bowlder clay. 



1. This formation is shown with great distinctness and in very numer- 

 ous exposures in Butler county. Almost every stream in some portion 

 of its course discloses it. Its general composition has been fully enough 

 described in previous reports. A particular feature of the bowlder clay 

 in Butler county is that of ancient vegetable growths, branches, trunks 

 and roots of trees in large quantities. Examples can be seen in follow- 

 ing almost any stream to its source, but one or two points may be named 

 which are specially noteworthy in this respect. Collins' Run, near Ox- 

 ford, a small tributary of Pour Mile Creek, shows in its banks very 

 numerous exposures of these pre-glacial and inter-glacial forest growths. 



