36 J. J. STEVENSON CARBONIFEROUS OF APPALACHIAN BASIN 



variable; there was supposed to be only one bed and the conditions there 

 observed were applied throughout the Pennsylvania areas. Later studies, 

 supplemented by records of shafts and borings, make it possible to cor- 

 rect the writer's error of 30 years ago. 



The Lower Sewickley coal bed is the Sewickley of most of Greene, 

 Washington, and Allegheny counties, Pennsylvania, as described in 

 volume K of the Pennsylvania reports. It is the persistent bed of 

 Payette and Westmoreland counties within the Connellsville basin, but 

 it is very indefinite in the Lisbon. The horizon is well marked by the 

 Pishpot limestone below and the Sewickley sandstone above, between 

 which one usually finds either coal or black shale. The bed is of work- 

 able thickness at some localities in Payette and Greene counties of Penn- 

 sylvania and it is a well marked coal horizon in West Virginia, being 

 noted in very many oil-well records at 25 miles south from the Penn- 

 sylvania line. In northern Ohio it is present in Belmont and perhaps 

 , Monroe county as coal, but very thin. Its extent is much less than that 

 of the Pittsburg, the interior area in which it is wanting being much 

 greater. 



The Sewickley sandstone (I. C. White, 1891) is a remarkably per- 

 sistent deposit, 5 to 40 feet thick, recognized throughout Pennsylvania 

 and northern Ohio and very distinct in West Virginia to at least 40 

 miles south from the Pennsylvania line. It is present in many oil- 

 well records, even into the central area of West Virginia. ISTear Union- 

 town, in Payette county of Pennsylvania, it is wanting in a shaft where 

 the Sewickley coals have united, the resulting bed separating the Fish- 

 pot and Benwood limestones. In the southwest part of that county 

 the sandstone gradually decreases and the Upper Sewickley coal bed is 

 let down almost to the Pishpot limestone. 



The Upper Sewickley coal bed. Maryland: Gas, Tyson. Pennsylvania: Se- 

 wickley. West Virginia : Sewickley. Ohio : 

 VIIIc, X, Cumberland, Meigs creek. Macks- 

 burg, Upper Barnesville. 



This is an important coal bed near Prostburg, in Maryland; it is unim- 

 portant in the Connellsville basin, where one finds at its horizon only 

 black shale, but in western Fayette and Westmoreland it is persistent as 

 coal, almost directly underlying the Benwood limestone; and there, as 

 in the adjacent portions of Washington county, it is occasionally thick 

 enough to be mined. In much of Washington and Allegheny counties 

 it is little more than black shale, but when it comes up again on the 

 westerly side, in the West Virginia panhandle, it is coal in two or three 



