60 J. J. STEVENSON PENNSYLVANIA ANTHRACITE. 



Thus far, it is sufficiently clear that the comparison affords no basis 

 for the assertion that the Measures are thicker, materially thicker, in the 

 anthracite than in the bituminous regions. It is impossible to make 

 similar comparisons in detail for the upper groups, since they have not 

 been differentiated finally from the lower barren group in the anthracite 

 fields. At the same time, there is no reason to doubt that both the 

 upper coal group and the Permo-Carboniferous are present in the anthra- 

 cite region, for 2,250 feet of rock are reported * as overlying the Mammoth 

 bed at Pottsville. The Pittsburg bed has been identified with much 

 hesitation in one of the anthracite fields, but there is no doubt respecting 

 the identification in the Cumberland field and but little in the Broad 

 Top field. It is certain, however, that groups 4 and 5 attain their 

 greatest Pennsylvania thickness in the extreme southwest corner of the 

 state, and that in all directions from that locality ,* within the state, they 

 decrease in thickness. This appears abundantly by comparison of 

 measurements made by Professor I. C. White and by the writer in Ohio 

 and various portions of Pennsylvania.f There is every reason, therefore, 

 to believe that they are less thick in eastern than in western Pennsylvania. 



Increased Rock-covering not found to produce Anthracite. — Measurements 

 made in Virginia and West Virginia by I. C. White, Fontaine and 

 Stevenson show conclusively that the thickening of the Coal Measures 

 was not greatest, was not even great, in the anthracite region or at any 

 other locality in Pennsylvania. Long ago Fontaine measured the Potts- 

 ville group on the New river and announced the thickness to be not far 

 from 1,200 feet. The writer found 1,000 feet in Wise county of Virginia ; X 

 while Professor I. C. White measured 1,400 feet at one locality in Fayette 

 county of West Virginia,§ and announced that in Kentucky the thick- 

 ness reaches 2,000 feet. On the Big Kanawha river of West Virginia 

 Professor White finds the lower coal group 1,006 feet thick, while the 

 lower barren group is 800 feet.|| Still further south, in Wise county, 

 Virginia, many miles beyond the extreme southern limit of the Pitts- 

 burg coal-bed, as determined by Professor White, the writer found 2,348 

 feet of coal measures above the top of the Pottsville,^ which can represent 

 only the lower coal group and the lower barren group. It is, therefore, 

 unquestionably certain that the thickness in the anthracite fields is very 

 much less than in eastern Kentuck}^ and the southern portion of the 



*Ashburner : Second Geol. Survey Pennsylvania; First Rep. on the Anthracite Coal Region, 

 1883, p. 239. 



t Stevenson : The Fayette and Westmorehand District; 1878, part 2, chap, xxi, pp. 283-295. 



t Stevenson : Proc. Amer. Philos. Society, voL 19, 1881, p. 230. 



'i I. C. White ; Stratigraphy of the Bituminous Coal-field of Pennsylvania, Oliio and West Virginia 

 Bulletin U. S. Geol. Survey, no. 65, 1891, p. 197. 



II I. C. White : Loc. cit., pp. 85 and 140. 



^ Proc. Amer. Philos. Society, vol. 19, p. 238. 



