276 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



mainly till. A short distance from Williamsburg, on the road toward Bethel, 

 rock outcrops up to a level only 16 or 20 feet below the level of the uplands, 

 or much above the level of the rock surface in East Fork Valley. The 

 peculiar drift structure at Bethel was noted above (p. 273). Granite bowl- 

 ders are found on the surface in the vicinity of Bethel, which are, in some 

 cases, 8 or 10 feet in diameter. Similar bowlders are reported from the 

 vicinity of Russellville, in Brown County. 



East of Bethel, near Hamersville, on an elevated ridge standing about 

 975 feet above tide, the drift is thin, being only 10 to 20 feet in thickness, 

 and the altitude of the rock surface is 90 to 100 feet higher than at Bethel. 



The drift is thin on the uplands on either side of White Oak Creek, in 

 the vicinity of Georgetown, scarcely exceeding 20 feet. 



The drift at Winchester has a thickness of only 10 feet in the eastern 

 part of the village, but exceeds 20 feet in the northern and western parts. 



Drift exposures are numerous between Winchester and Seaman, the_ 

 first railway station toward the east, but farther east there are only scattering 

 patches of drift or occasional bowlders. 



The general thickness of the drift along the Baltimore and Ohio Rail- 

 road in Brown and Clermont counties and between that railroad and the 

 outer Wisconsin moraine is 20 feet or less, or an amount scarcely half that 

 found in a trip through attract 12 to 20 miles to the south. This thickening 

 does not, however, assume the form 'of a ridge, but as previously noted, 

 simply serves to fill up preglacial inequalities of surface to a somewhat 

 uniform level. 



From the Little Miami Valley westward across Hamilton County, Ohio, 

 there is a nearly continuous sheet of till, the thickness of which on the 

 uplands seldom exceeds 20 feet, but in lowlands and valleys sometimes 

 reaches 100 feet or more. 



South of the Ohio River there is not so continuous a sheet of drift. 

 Pebbles and bowlders of Canadian derivation constitute one of the con- 

 spicuous features. There are also deposits of a sandy, or more frequently 

 clayey character, through which Canadian rocks are sparingly distributed. 

 In these deposits many local rock fragments occur. They usually bear 

 but slight resemblance to ordinary till, though the presence of granite or 

 other distantly derived pebbles is evidence that they were acted upon by 

 the ice sheet. They appear to be in the main only the slightly disturbed 



