DUI^KARD FORMATION 101 



lying a great mass of black shale, while at a mile away the carbon is 

 gathered into four benches and the bed is 6 feet 6 inches. The bed is 

 usually thin in eastern Washington and Greene, but along the same area 

 in Marion county of West Virginia it thickens and one section shows 

 10 feet 9 inches in 14 layers of coal and clay. Along the Baltimore and 

 Ohio railway it is exposed frequently in Doddridge and Eitchie counties, 

 showing the same complex structure observed at the northern exposures. 

 Still farther south, in Calhoun and Eoane counties, it is thin, rarely 

 exceeding 2 feet 6 inches and containing, as so often at the north, the best 

 coal at the bottom. Toward the west it becomes thin, being only 1 foot 

 3 inches in Ohio of West Virginia and reported in Ohio only as a blossom. 



Almost without exception, coal from the Washington is inferior to 

 that from the Waynesburg; yet it is mined for domestic fuel in a great 

 area within the middle portion of the great trough, where the lower coals 

 have disappeared. The coal-making conditions extended for the first 

 time over practically the whole area, a notable change in geographical 

 conditions. 



The interval between the Washington coal bed and the Upper Wash- 

 ington limestone contains five important limestones and three coal 

 horizons. 



The Lower Washington limestone (J. J. Stevenson, 1876), 3 to 15 

 feet above the Washington coal bed, has been recognized in Maryland, 

 and it is present at almost all places in Penns3dvania where its horizon 

 is exposed. Doctor White has recognized it on the eastern side in West 

 Virginia as far south as Tyler and northern Harrison, but toward the 

 west it becomes insignificant, being very thin along the Ohio river and 

 apparently wanting in most of Ohio. It is thin and often only calcareous 

 shale in most of eastern Washington, but in the central part of the 

 county it is from 15 to 33 feet thick, while on the west side it varies 

 from 6 inches to 20 feet, these measurements being separated by only 

 half a mile. In Greene county it rarely exceeds 3 feet. In Ohio county 

 of West Virginia it is 20 feet thick at a few miles east from Wheeling, 

 though thin at that city and apparently wanting 4 miles south at Bellair, 

 Ohio. It usually imderlies a black shale rich in carbon and often con- 

 taining fish remains. 



The Blackville limestone (I. C. White, 1891), III of volume K, at 

 25 to 70 feet above the Washington coal bed, is not reported from any 

 locality east from the Monongahela river except in Eedstone of Fayette 

 county, Pennsylvania, but it is persistent in Allegheny, Washington, and 

 Greene counties. It is not more than 3 or 4 feet thick at the most north- 



