350 ~ GEOLOGY OF OHIO. 
trates the crushing force of these agencies. The rock is broken and 
displaced as if by a lateral thrust exerted upon both sides of the hill with 
a force sufficient to break up the rock to its center, but not sufficient to 
carry it away. Between Utica and Homer are Drift clay hills, with 
eranitic bowlders, rising to the height of seventy-five feet above the valley. 
The north-western part of the county isa succession of undulating 
hills, rising to a height of 495 feet above the railroad at Newark, deeply 
covered with typical clay Drift, with few rock exposures, these all Wa- 
verly. The timber is largely beech and maple, with a mixture of oak, 
ash, and elm. The roads often lead over clay ridges rising from forty- 
five to seventy-five feet above the intervening hollows, the only rocks 
exposed being erratics of the Drift. Approaching these undulating Drift 
hills from the south and southeast, the observer would note the outcrop 
of the Waverly rocks, covered with their own debris, and no evidences 
of the Drift except occasional erratics. Passing southward, the high hills 
about Granville are covered wholly with the debris of the lecal rocks, but 
in the valleys there are yet remaining heavy deposits of bow!der clay, 
extending to an unknown depth below the present surface of the streams. 
At acut in the Atlantic and Lake Hrie Railroad, south-east of Granville, 
the blue bowlder clay, with occasional striated pebbles, is exposed, of the 
thickness of fifty feet, and in places is known to underlie the gravel beds 
of the streams. This clay is sometimes wholly unstratified, containing 
2? 
a profusion of metamorphic and granitic pebbles, some of them well 
rounded, others angular, oblong, and striated, and mingled with the debris 
of the limestones and the local rocks. | 
In the south-eastern part of the county the hills are covered only with 
‘the debris of the local rocks, conspicuous among which is the flint of 
“Flint Ridge,” the evid: nces of the Drift being found only here and there 
in the valleys, and mainly in the form of pebbles in the gravel banks 
and beds of the streams. | 
The following is a section of the materials disclosed by a small stream 
a little west of Linville: 
1. Stratified gravel, rising to the top of the hi!ls adjoining the stream. 
2. Kinely laminated, compact blue clay, similar to that found upen the north 
side of the divide which separates the waters of the Luke from those of 
the Ohio, and in the deep valleys penetrating the divide from the north. 
Among the hills the ravines are the result of recent erosion. This 
erosion is largely determined by the location of subterranean water- 
courses, supplemented by the geological structure. The fire-clays of the 
Coal Measures, and the argillaceous shales alternating with the harder 
