344 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



it evident that it marks a part of the marg-in of a glacial lobe. The sharp 

 gravel knolls which appear near the line of the moraine in the vicinity of 

 Hillsboro apparently belong to the Illinoian or earlier ice invasion, as 

 already indicated. 



In eastern and central Highland County the moraine presents in its 

 outer portion gentle swells of till, 5 to 15 feet in height, each covering areas 

 of 1 to 10 acres or more. Northwest from the Maysville Railway, in sur- 

 vey 2480, small gravelly knolls 10 to 20 feet or more in height abound, 

 several of which are in view from the Cincinnati pike west of Hillsboro. 

 From survey 2480 northward to survey 2351, a distance of about 4 miles, 

 there are no well-defined morainic features. 



In northwestern Highland, in Clinton, and in Greene counties there 

 is, aside from the main ridge, which stands 20 to 40 feet above the outer 

 plain, a moderate number of small knolls and gentle swells 10 to 20 feet in 

 height. The majority of these swells are conical, or but slightly elliptical. 

 When elliptical, the trend of the longer axis is usually in line with the 

 moraine, whose trend there is from east of north to west of south. 



STRUCTURE AND THICKNESS OF DRIFT. 



In the main the drift consists of till, but, like most other moraines and 

 also the intermorainic drift sheets, considerable variation is frequently- found 

 within short distances, owing to the presence of local beds of assorted 

 material which occur at various depths. It is from these beds that the 

 wells of the region usually derive their water supply. But in Highland 

 County, in the ^acinity of Hillsboro and thence down Rocky Fork, as has 

 been noted, large gravel knolls occur. The gravel in these knolls is largely 

 composed of limestone pebbles, and much of it near Hillsboro is cemented, 

 and in general it has the aged appearance of the earlier drift. It shows 

 strata in various attitudes, but where opened extensively horizontal stratifi- 

 cation predominates. 



The lower limit of this sheet of drift is in places shown by a buried 

 land surface, having a soil and peaty deposits. The buried soil is found at 

 Marshall, as has been noted by Orton, and many wells reported to the 

 writer'in Martinsville and some at Wilmington strike it. It is well exposed 

 along a ravine in the south part of Wilmington, as described below. 



The buried soil, wherever noted in Highland and Clinton counties, is 



