720 GEOLOGY OF OHIO. 
The following notes on the geological extent and character of the dif- 
ferent groups of rocks which have been enumerated will suffice with 
what has gone before to give a clear idea of the general geological struc- 
ture of the county. 
THE UPPER COAL GROUP. 
The Coal Measures of Ohio show more or less distinctly four divisions, 
corresponding to those which have been described by Prof. Rogers in his 
Report on the Geology of Pennsylvania, and named by him: 
Ist. The Upper Barren Measures. 
2d. The Upper Coal Group. 
3d. The Lower Barren Measures. 
Ath. The Lower Coal Group. 
The Upper Barren Measures are hardly shown anywhere in Ohio 
except in Monroe county, where the deepest portion of the coal basin 
occurs. Here the highest hills are formed chiefly of a mass of shale con- 
taining no important coal seams, and which overlie the workable coals _ 
of this and the adjoining counties, and form the summit of the geolog- 
ical series in Ohio. Below the Upper Barren Measures is found a group of 
six or seven coal beds, distributed through about three hundred and fifty 
feet of shales, sandstones, limestones, etc., constituting the Upper Coal 
Group. Of these the lowest is the Pittsburgh seam, or Coal No. 8, of the 
Ohio series. Immediately above this there are sometimes two or three 
small coals, which have been numbered 8a, 8), and 8. Following these 
are Coals Nos. 9, 10, 11, 12, and 13, which, with the exception of Coal 
No. 10 (@ persistent and important seam south of the National Road), are 
generally thin, or of inferior quality, and have only local importance. 
In the southern part of Jefferson county, back from the river, in the 
townships of Mt. Pleasant and Smithfield, the surface rises in some 
places nearly three hundred feet above the horizon of Coal No. 8, and the 
highlands contain Coals 8a, 8b, 8c, and 10, 11, and 12. Coal No. 9 is gen- 
erally absent, and Coal No. 12 present only in the hill tops. 
_ This series of coals above No. 8 is here of little economic importance. 
They rarely exceed a foot to eighteen inches in thickness; and where 
reaching, as Coals Nos. 10 and 11 sometimes do, workable dimensions 
(two to three feet), they are of inferior quality. Hence it will be seen | 
that the Upper Coal Group, with the exception of Coal No. 8, can con- 
tribute little to the mineral wealth of the county. 
An interesting fact has been brought out by Prof. Stevenson in his 
study of the geology of Belmont, Harrison, and the southern townships 
of Jefferson, viz., that all the Upper Coal Group, with their associated 
