THE CARBONIFEROUS SYSTEM. 93 



grained sandstone. It is also met with at a varying distance below the 

 Berea grit in all the exposures of the Waverly series in southern Ohio, 

 but shows a marked diversity of thickness at different places. In the 

 gorge at Bedford, where it is entirely cut through, it is 21 feet in thick- 

 ness; at East Cleveland, as has been stated, 54 feet; in the section from 

 Painesville to Little Mountain, 30 feet; in the valley of Black river, 50 

 feet ; and in the valley of the Vermilion, from 60 to 80 feet. In the lat- 

 ter section of the State, as has been before stated, the underlying Erie 

 shales thin out, and the Cleveland shale approaches very closely to the 

 lower black shale (Huron shale), which has here a great development. 

 From this point south to the Ohio river the Cleveland shale is met with 

 in various sections of the Waverly, but diminishing in thickness in this 

 direction. At Freestone a layer of bituminous shale, probably its equiv- 

 alent, lies directly beneath the City Ledge, and has a thickness of 16J feet. 



Throughout its entire extent the Cleveland shale has nearly the same 

 lithological characters, though differing somewhat in the relative quan- 

 tities of its carbonaceous and mineral ingredients. It generally contains 

 from 10 to 20 per cent, of combustible matter, and when freshly quarried 

 is a tough, compact rock. Upon exposure, however, it splits into a great 

 number of leaves, so that its outcrops form slopes covered with small, 

 thin scales of the rock. By weathering, the carbonaceous matter is 

 eliminated from the surface, and it becomes gray in color, except where 

 stained, as it often is, by the oxide of iron. 



The fossils of the Cleveland shale have, until recently, altogether 

 eluded the search of geologists ; but during the prosecution of the survey 

 we have been able to gather quite a large number from different locali- 

 ties, some of which are of considerable interest. 



In entering upon the study of the Lower Carboniferous group of rocks 

 in Ohio, the Cleveland shale formed our point of attack, and knowing 

 from experience in the Carboniferous and Cretaceous rocks that, "given 

 a bituminous shale, fish scales were almost a logical sequence," these 

 were the first objects of search. Within a few minutes after beginning 

 such search they were found in considerable numbers in the exposures 

 at Newburgh. Subsequently the scales of fishes were met with in all the 

 localities where this rock was examined. These are generally minute, 

 rhomboidal, enameled scales, and, as we now know, belong to a species of 

 Palseoniscus. IAngula and Discina — like fish scales, the usual concomi- 

 tants of black shales — were also found in various localities. The most 

 interesting group of fossils, however, obtained from this stratum was dis- 

 covered by Captain Jas. Patterson, near Vanceburg, Kentucky. In exca- 

 vating the shale at one horizon, he found a surface covered with the re- 

 mains of fishes — teeth, spines, bones, dermal tubercles, etc. 



