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, Hammondsviile, CoUinwood, 

 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 (76), 

 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 ^eet 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 Hammondsviile, Coals No. 3, 4, 5, 6, and 7 are exposed. Going 

 towards Saline ville, on the railroad. Coals No. 3 and 4 pass under the 

 ©reek 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 Hammondsviile 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. 6 is here about four feet thick, and some 



