DELAWARE COUNTY. 



30.5 



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, South Part of Radnor Township. 



w w 



1. Soil and hard-pan, 2 feet. 



2. GraTel 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, :! }et they are less prominent than somt others that have been de- 

 scribed in north-western Ohio. (See Report on the Geology of Hardin 

 county, also Report on Geology of Allen count} .) 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 transportable 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 m.,rs;in of the glacier finally" passed 

 northward over any point on such boundary line, the final effect of th 

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