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730 GEOLOGY OF OHIO. 
characteristics of certain subordinate districts of special interest with 
the local groupings of geological facts, as illustrated by mining or man- 
ufacturing enterprises, will now be described. 
THE YELLOW CREEK VALLEY. 
The greater part of the valley of the north fork of Yellow Creek lies in 
Columbiana county, and its geological features are given in the report 
of that county, but the stations of Irondale, Hammondsyille, Collinwood, 
and Linton, are within the limits of Jefferson, as are the valleys of 
Brush Creek and the south fork of Yellow Creek (Big Yellow Creek). 
These latter streams have their sources in Carroll county, but drain the 
townships of Brush Creek, Springfield, Ross, Saline, and Knox. The 
summits of the hills in Brush Creek and Saline rise two hundred feet 
into the Barren Coal Measures, and are capped with the crinoidal lime- 
stone. Further south, in Knox, Ross, and Saline, the highest points 
contain the Pittsburgh coal and limestone, and hence all the upper 
portions of the valleys of the streams mentioned lie in the Barren Meas- 
ures and contain no workable coal, except where the Harlem seam (7b), 
as it sometimes does, attains a thickness of two and a half feet, and is 
sparingly worked. ‘The altitude of Robinson’s point is about six hun- 
dred and eighty feet above Lake Erie, and the surface is one hundred 
and fifty feet above the crinoidal limestone. The highest rocks of this 
vicinity are in the upper portion of the Barren Measures, reaching to 
within about fifty feet of the Pittsburgh coal. They are mainly yellow 
friable sandstones above, and soft olive shales below to the crinoidal 
limestone. About ten feet above the limestone, a seam of coal from 
twelve to eighteen inches thick occurs. The crinoidal limestone is here 
from three to eight feet thick; the Harlem coal thirty inches. 
At Hammondsville, Coals No. 3, 4, 5, 6, and 7 are exposed. Going 
towards Salineville, on the railroad, Coals No. 3 and 4 pass under the 
creek at New Salisbury, and No.5 at the Big Cut. Coal No. 6 sinks 
below the bottom of the valley just below the village of Salineville, but 
comes out again at the station and rises rapidly towards the west and 
north, so that No. 5 is shown at the old salt well on the switch. 
In following up the valley of Big Yellow Creek, almost precisely the 
same geological structure is observable. Between Hammondsville and 
the mouth of Brush Creek, Coals 3 and 4 pass beneath the surface, and 
are not again seen. Above the mouth of Brush Creek, Coals No. 5, 6, 
and 7 descend until No. 5 disappears, and No. 6 is just on the level of 
the Creek. At the Tunnel Mill the strata rise again, and Coals Nos. 5, 
6, and 7 are all exposed. No. 6is here about four feet thick, and some 
