646 GEOLOGY OF OHIO. 



The Niagara rock is ill-adapted to building purposes, coming out of the 

 quarry in massive and ungainly blocks; but the close proximity, in this 

 region, of the fine courses of the Waverly quarries renders it unnecessary 

 to turn it to such uses. 



2. The Huron shales are, perhaps, the most characteristic formation 

 of the western half of Ross county. They occupy a large area, and im- 

 press peculiar features upon the soil, the vegetation, and the scenery. 

 They afford at Benner's Hill, above mentioned, the heaviest section 

 yielded by the formation in Ohio, viz., three hundred and thirty-two feet. 

 The composition of the series, as shown in this and closely adjoining 

 sections, has two points that deserve mention. The first is the occur- 

 rence of twenty-six feet of white and blue clays at the base of the series ; 

 and the second, which is much the more interesting observation, is the 

 occurrence of a calcareous layer, well charged with fossils, at the height 

 of forty to fifty feet above the base of the system. The clays are shown 

 on the west side of Benner's Hill. The limestone seam is best seen at 

 Ferneau's Mill, one mile east of Bainbridge. Mr. J. H. Poe, of Chilli- 

 cothe, first called attention to its existence, and to him the Survey is in- 

 debted for a very interesting fossil — the body of an hitherto undescribed 

 crinoid — obtained from this locality. The calcareous seam varies be- 

 tween three inches and six inches in thickness. Its composition is 

 shown in the appended analysis, made by Prof. Wormley : 



Silicic acid 53.20 



Iron and alumina 2.10 



Carbonate of lime 37.20 



Carbonate of magnesia 6.88 



99.38 

 Its interest lies in the fact that.no other such seam has been reported 

 in the whole extent of this formation. Taken as a whole, the Huron 

 shales are almost entirely destitute of traces of either vegetable or animal 

 life. Two brachiopod shells, a Discina and a Lingula, have been found at 

 various points in the system, and the great concretions which the forma- 

 tion holds have yielded the remains of some remarkable species of fishes ; 

 but throughout most of its extent it is utterly barren of palseontolog'ical 

 interest. One of the difficulties in settling the Ohio geological scale, or, 

 at least, of correlating certain of its upper members with the members of 

 the eastern geological series, has lain in the fact that fossils, the true 

 labels of the rocks, are here wanting. The outcrop of the slates on the 

 western side of Ross county promises valuable contributions to our 

 knowledge of the life of the seas and shores during the long period in 

 which these black shales were accumulating upon the floor of the an- 



