62 J. J. STEVENSON PENNSYLVANIA ANTHRACITE. 



Sewell mountain region ; yet its volatile is no greater than that of the 

 same coal at Pocahontas, in Virginia, at a little way from the Abb's val- 

 ley fault, whose throw is more than 10,000 feet. The crushed " looking- 

 glass " coal in the Broad Top field is semi-bituminous, while the un- 

 crushed coal of the gently flexed Wyoming field is anthracite. The 

 Barnet bed in the Broad Top field is faulted, but shows coal of the same 

 quality on both sides of the fault. The Imboden coal-bed of Wise 

 county, Virginia, at only a stone's throw from the great overturned anti- 

 clinal of Stone mountain, has about 37 per cent of volatile, quite as much 

 as it has miles away at the west in the undisturbed portion of Kentucky. 

 Evidence of the Arkansas Coals. — Mr Winslow's observations in Arkansas 

 afford another illustration which is in place here. Evidently inclined 

 favorably to the doctrine of metamorphism by heat derived from crush- 

 ing, he regards as somewhat curious the fact that the volatile combustible 

 in the Arkansas coals diminishes as the distance from disturbance in- 

 creases, for the region of high volatile is traversed by flexures recalling 

 to mind the systems in Pennsylvania, whereas the region of the semi- 

 anthracite is undisturbed.* 



Metamorphism not a sufficient Explanation of the Phenomena. 



While there can be no doubt that bituminous coal, heated by contact 

 with molten rock, or by transformation of mechanical force exerted in 

 crushing rock, or by action of gases or vapors from deep-seated sources, 

 may become anthracite, still it must be conceded that in Pennsylvania 

 there is no evidence showing any relation of cause and effect between 

 such agencies and the loss of volatile combustible in the coal. Some 

 explanation other than that depending on metamorphism must be found; 

 for if metamorphism be unnecessary to explain the variation of volatile 

 from 45 to 35 per cent in the same coal-bed within a few rods, it should 

 be equally unnecessary to explain a still further loss of volatile. The 

 more so, in view of the well-knoAvn fact that difierent benches of the 

 same bed at the same opening, where they are separated by only a few 

 inches of clay, show a contrast greater than that betw^een the Pittsburg 

 coal in the Salisbury bituminous basin and the Stoney creek coals of 

 the Southern anthracite field.f The volatile often differs several per 

 cent in the different benches of a coal-bed. Even in the same hillside in 

 the Bernice or Loyalsock field (the northern end of the first bituminous 

 basin) and barely 60 feet apart are two beds, the lower showing a ratio 

 of 4.13,J while that of the upper bed is 10.28. 



*Winslow: Log. eit.. p. 51. 



t Ann. Rep. Second Geol. Survey of Pennsylvania for 1885, pp. 480^ 482, 485. 



I A. S. McCreath : Second Rep. of Progress in the Laboratory, etc, pp. 82-94. 



