132 THE JOURNAL OF GEOLOGY. 



Highland, Adams and Brown counties, Ohio, there is a discon- 

 tinuous or patchy deposit of drift, consisting in places only of 

 scattering bowlders. In other places it consists of a clayey 

 or sandy deposit, in which a few erratics are imbedded. In 

 still others, notably at Split Rock and along Middle creek, west 

 of Burlington, Kentucky, it consists of cemented coarse gravel. 

 Only occasionally in the border portion is there a deposit of 

 thoroughly commingled drift or typical till such as characterizes 

 the thicker drift sheet immediately north. The attenuation seems 

 due more largely to original deposition than to subsequent 

 erosion. 



Over the greater part of this earlier drift district back from 

 the attenuated border one finds a nearly continuous deposit of 

 till ranging from a few feet up to one hundred feet or more in 

 thickness. It displays little or no aggregation in morainic knolls 

 or ridges. The greatest thickness is found in fiUed-up valleys 

 or in depressions, though the uplands in places carry as much as 

 fifty feet of drift. Where less than twenty feet in thickness this 

 drift sheet consists in the main of a yellow till. Where the 

 drift has greater thickness a blue till is commonly found beneath 

 the yellow. The blue till abounds in joints or irregular fissures 

 filled with yellow or oxidized clay, a feature which is rare in the 

 later drift sheet, and may, perhaps, constitute an important line 

 of evidence as to the age. Both the yellow and the blue till 

 are harder than those of the newer drift. The indurated char- 

 acter of this earliest drift sheet is apparently due to a partial 

 cementation with lime, the drift being highly charged with a 

 calcareous rock flour, a glacial grist. 



The earlier drift seems to have been deposited in this district 

 without great abrasion of the rock surface. No strige have been 

 found, though repeated search was made for them. (In districts 

 further west striae are occasionally found beneath the earlier 

 drift). Between the blue till and the underlying rock there are 

 frequent exposures of a few feet of earthy material having the 

 appearance of residuary clay, or, if this be absent, a very rotten 

 rock surface is usually found. In one village (Mt. Oreb) well 



