Stevenson.] ^OO [Dec. 18, 



and in Upshur and Randolph Counties it does divide. Its partings 

 thicken up and from mere flimsy plates become layers of shale several fef t 

 thick, so that the coal usually only three or four feet thick further north, 

 is gradually converted into a mass of shale and coal upwards of twenty 

 feet thick, which at one locality includes a thin layer of sandstone. 



Loioer Barren Groiqo. — So interesting is this group in itself, and so 

 irregular are its rocks, that it deserves consideration only because it 

 occupies the interval between the Upper Freeport and Pittsburgh seams, 

 two beds, which seem to be the most persistent of all found in the Coal 

 Measui'es. It is separated into two divisions by a well marked stratum 

 which in Ohio is known as the Grinoidal Limestone, and in Pennsylvania as 

 the Fossiliferous Limestone. This I have traced from the Muskingum River 

 round through Pennsylvania into West Virginia, where, like nearly all 

 the Coal Measui-es Limestones, it disapjjears in the vicinity of the Balti- 

 more and Ohio Railroad, south from Grafton. At the western exposure 

 of the Pittsburgh in Ohio, this limestone is 140 feet below it. Northeast- 

 ward the interval becomes successively 140, 160, 175, 190, 300, and near 

 Steubenville and along the Ohio River 225 feet. In Pennsylvania on the 

 Monongahela River, it is 320, and near Morgantown, West Virginia, 270. 

 In like manner we find a varying interval between it and the Upper Free- 

 port. At the most western exposure of the limestone this interval is 

 225, further east 280, at its northerly exposure 260, and at Steubenville , 

 on the Ohio, 280 feet. At Morgantown it is 172 feet. 



The total interval between the Pittsburgh and Upper Freeport, varies 

 in thickness in Ohio, from 420 feet at the west, to 505 at Steubenville, 

 the increase being regular toward the east. In Pennsylvania it is 200 

 feet, at Ligonier, 220 at Elk Lick, and on the Monongahela River from 

 450 to nearly 600 feet. In West Virginia, along the Monongahela and 

 Tygarts Valley River, it varies not much from 420 feet. 



Upper Coal Oroup. — The following table shows the synonyms of the 

 coals of this group. 



Ohio. Pennsylvania. West Virginia. 



XIIT. Top at Waynesburg. Not identified. 



XII. Second Waynesburg. Brownsville. 



XL Waynesburg. Waynesburg. 



X. Uniontown?? Absent. 



IX. Absent. Absent. 



VIIIc. Absent. Absent. 



VIII6. Sewickley. Sewickly. 



Villa. Redstone. Redstone. 



VIII. Pittsburgh. Pittsburgh. 



In this group the wedge shape of the strata is more distinctly shown 

 than in either of the lower groups, partly because of the persistence of 

 the coal seams and partly because of the long continuous sections which 

 can be obtained over a great extent of country. In it too, there is a 



