DELAWARE COUNTY. _ 305 
lime. There is a general but very gentle slope to the west. The mate- 
rial in these ridges is stratified sand and gravel, which has been consid- 
erably used in constructing the gravel roads that intersect that part of 
the county. One of these sand and gravel deposits is opened for such 
purposes on the land of Mrs. Rachel Fleming, on the east side of the 
Scioto, near the mouth of Bogg’s Creek, and shows the following alter- 
nation of parts: 
SECTION IN GRAvEL Bank, Sourn Parr or Rapnor Townsup. 
=) 
; Sf heer 
aS S 
1. Soil and hard-pan, 2 feet. 
2. Gravel and sand; stratification confused or wanting. 
3. Handsome strata of sand obliquely stratified. 
The outward appearance and composition of this series of gravel ridges 
are the same as of those ridges well known in the country as “hogs’- 
backs,” yet they are less prominent than some others that have been de- 
scribed in north-western Ohio. (See Report on the Geology of Hardin 
county, also Report on Geology of Allen county.) Their long continu- 
ance and their more uniform height make them in some respects com- 
parable to those very long gravel ridges that have been described in 
north-western Ohio, and referred to the effect of glaciers crossing a num- 
ber of counties consecutively. Their real origin, however, is not that of 
terminal glacier moraines, but is the same as of those isolated gravel 
knolls known as “hogs’-backs.” Similar lines of gravelly, rolling land 
following and marking the boundary between two geological formations 
have been mentioned in reports on the geology of Crawford and of Mor- 
row counties. Such boundary lines, when between two formations of un- 
equal endurance under the glacier, would be the place where most fre- 
quently deep fissures in the ice would be produced by the efforts of the 
great sheet to adapt itself to the unevenness of its bed. In such fis- 
sures, and along such openings, running water would appear, and would 
most effectually carry away the stransportable clayey portions of the 
Drift with which it might come in contact. During the prevalence of 
the ice, such washed and, perhaps, stratified Drift would be liable to a 
further transportation, but when the n:.rgin of the glacier finally passed 
northward over any point on such bounda ‘y line, the final effect of th 
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