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 

 granitic bowlders, rising to the height of seTenty-five feet above the valley. 



The north-western part of the county is a 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 local rocks, but 

 in the valleys there are yet remaining heavy deposits of bowlder clay, 

 extending to an unknown depth below the present surface of the streams. 

 At a cut in the Atlantic and Lake Erie Kailroad, 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 

 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 evidtnces 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 hills adjoining the stream. 



2. Finely laminated, compact blue clay, similar to that found upon the north 



side of the divide which separates the waters of the Lake from those of 

 the Ohio, and in the deep valleys penetrating the divide <rom 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 



