68 J. J. STEVENSON PENNSYLVANIA ANTHRACITE. 



attains to local importance. The same contrast appears for these groups 

 betAveen the anthracite region of Pennsylvania and the bituminous areas 

 of West Virginia, as Professor White has shown.* 



Comparison of sections representing the upper coal group shows that 

 the conditions were changing in the Southern field, for the upper beds 

 are thin, seldom exceeding 2 or 3 feet; the same is true of the western 

 Middle, but in the Northern the change is not so marked, the higher 

 beds comparing very favorably with those of the lower barren group. 

 The greatest thickness in the 400 feet taken as equivalent to the upper 

 coal group of the bituminous areas is 26 to 29 feet in the Northern, 25 

 feet in the western Middle and 11 to 12 feet in the Southern anthracite 

 field. In the Broad Top field the coal in all, counting partings, does not 

 exceed 7 feet in a section of 260 feet. Tyson f found 36 feet of coal-beds 

 in the Cumberland basin, but his description does not tell how much of 

 this is coal. Professor White, however, found that in the 19 feet 8 inches 

 of Pittsburg coal-bed there are but 14 feet 6 inches of coal. The Salis- 

 bury basin of the first bituminous area shows 16 feet of coal-beds in 200 

 feet of measures, but further westward the thicknesses are so variable 

 that no estimates can be given that would be other than misleading. 

 The variations of the Pittsburg bed, however, can be followed without 

 difficulty. In the Cumberland basin it is 14 feet 6 inches ; in the Salis- 

 bury basin, 10 feet; in the Ligonier basin, 8 feet; in the Connellsville or 

 Coke basin it is from 6 to 9 feet; in the Greensburg, 6 to 7 feet 6 inches; 

 in the Lisbon, 5 to 7 feet ; but beyond that it rarely exceeds 5 feet, the 

 extremes in Ohio along the river being 4 feet 6 inches to 5 feet, while in 

 Guernsey county, on the northwestern outcrop of the bed, its thickness 

 is but 4 feet 2 inches. J Professor Andrews has stated that at its last 

 western outcrop the bed is not more than one foot thick. That is its 

 thickness in the center of the Appalachian basin in southern West Vir- 

 ginia. 



Conversion greatest in the northeastern Portion of Appalachian Basin. — It 

 is evident that the conditions favoring accumulation of coal in beds 

 lasted longer without interruption in the anthracite region than in any 

 other portion of the Appalachian basin, for the amount of coal decreases 

 westward and southward from that region. A comparison of thickness 

 of beds shows a tendency to greater regularity in a northeasterly direc- 

 tion within the first and second bituminous basins ; but it is unnecessary 

 and it would be very tedious to enter into the details of this comparison. 



*Bnlletin no. 05, U. S. Geol. Survej^ 



t Tyson: Second Rep. to House of Delegates of Maryland, 1862, p. 46. 



X These measurenients are taken from the writer's reports on Pennsylvania and Ohio. 



