656 GEOLOGY OF OHIO. 
quent in those parts.of south-western Ohio that hold the southern edges 
of the true Drift. Ross County is no exception to this statement, but it 
must be added that there have nowhere within its limits been found such 
districts as those around Marshall and New Market, Highland county, in 
which almost every well strikes into buried vegetation. 
Vie (DIPS OW TE SRRAIAY 
In concluding the discussion of this general area, a few facts will be 
given touching the dip of the strata that have now been described. ‘The 
appended map, which takes in Highland,»Pike, and Ross counties, fur- 
nishes the necessary data for determining approximately the amount and 
general direction of the inclination of the bedded rocks that underlie 
this district. The following points are used in this determination: 
Near the village of Samantha, five miles north of Hillsborough, the 
westernmost outlier of the Huron shales, or great black slate, is found. 
The line of junction between the limestones and the shales is perfectly 
distinct, and its altitude above tide-water has been ascertained. This 
point constitutes an initial station, and dotted lines are drawn from it 
to various localities, the altitudes of which above the sea are also known, 
where the same geological boundary is shown, or where other horizons 
that stand in a known relation to this one are to be seen. We find thus 
five main lines along which the dip can be calculated, ranging from east 
82° north to éast 40° south. 
The first of these lines is drawn from the initial station to a point in 
Ross county nearly opposite to Greenfield, a distance of fourteen and 
three-eighths miles. Its course is east 82° north. The fall of the lime- 
stone surface in that direction and that distance is two hundred and 
eight feet, which indicates an average dip of fourteen and a half feet to 
the mile. 
The next line extends from Samantha to Chillicothe, a distance of 
thirty-three and three-fourths miles, in a direction 9° north of east. The 
junction of the limestone and shales has now been carried below the sur 
face, but as the average thickness of the slates is known, it is possible to 
make their upper surface a basis for calculation. Allowing three hun- 
dred feet for the average thickness of this formation, the descent of the 
limestone in these thirty-three and three-fourths miles is found to be 
eight hundred and eighteen feet, or an average dip in this direction of 
twenty-four and one-half feet to the mile. Assuming the maximum 
thickness obtained from the shales, viz., three hundred and thirty-two 
feet, the dip would be increased by one foot—giving as the result twenty- 
‘five and one-half feet to the mile. 
