304 GEOLOGY OF OHIO. 
rest of the county was uncovered, and suffered all the vicissitudes of sur- 
face erosion. The average thickness of the Drift in Radnor township, 
judging by the phenomena of wells and the height of the river banks, 
as well as from the rocky exposures, is about twenty feet. Toward the 
river, bowlders are common on the surface. In Thompson township the 
thickness seems also to be eighteen or twenty feet. In descending the 
Scioto along the right bank, after passing Fulton’s Creek, there is a 
noticeable thickening of the Drift, and two Drift terraces follow the 
river for a couple of miles with considerable distinctness. They are 
each about fifteen feet in height, the upper one sometimes reaching 
twenty feet, and are separated in many places by a flat belt of land, the 
surface level of the lower terrace. Below these is the river flood-plain. 
This second, or upper river terrace, comes in apparently from the west, 
and appears just at the point where the rock begins to be excavated by 
the river. It makes the thickness of the drift about thirty or forty feet. 
After passing Millville and Sulphur Spring Station, the upper terrace 
disappears in a general slope to the river, and it cannot be identified at 
any point further south. This thickening of the Drift is in the form of 
a moraine ridge, which, passing west of Ostrander about.a mile, is inter- 
sected by the Marysville pike a little west of the county line. From its 
summit toward the west the descent is seventy-five or one hundred feet, 
when a flat is reached like that in the north-western part of Delaware 
county. This moraine has not been traced through Union county. The 
reader is referred to another chapter on the Drift in north-western Ohio 
by the writer for a full dissussion of this subject. 
A singular line of gravel knolls and short ridges pertaining to the 
glacier Drift crosses Radnor township, coming into the county from the 
north at Middletown (which ison the Scioto, in Marion county), and 
passing about a mile to'the west of Delhi. It is traceable nearly to 
Millville. It is intersected by the gravel road about a mile north of 
Delhi. The road then follows it to Middletown, where it becomes lost 
from further obervation. This interesting series of ridges is not ar- 
ranged in a single, continuous line, but the separate ridges overlap each 
other, rising and falling at irregular intervals. Sometimes the line ap- 
pears double ; low places on one side are in some places made up by full 
deposits on the other. On either side the country is flat. The soil is of 
close clay, and the roads very muddy in rainy weather. The Delhi beds 
of the Lower Corniferous are exposed at a number of places in close 
proximity to these gravel knolls, proving the strike of the formation to 
be exactly coincident with this strip of gravelly land. Toward the east 
is the enduring Corniferous; toward the west, the easily disrupted Water- 
