ANTHRACITE OF OTHER REGIONS. 45 



the strip becomes narrower and the folding more abrupt. Faults become 

 more markedly characteristic until in central and southern Virginia they 

 are to be looked for as the natural explanation of irregularities on the 

 eastern side of the strip. So much is this the case that one cannot well 

 draw a line by which to separate in southern Virginia the two areas of 

 Pennsylvania between the Alleghany mountain and the Blue ridge. 

 The Pocono coals are exposed again and again by the faults e-ven in the 

 Great valley, while the Coal Measures, in what must be taken as equiv- 

 alent to the anthracite strip of Pennsylvania, are involved for long dis- 

 tances in the faulted areas. The extent of the disturbance in Virginia 

 is much greater than at any locality in Pennsylvania, the faulting some- 

 times exceeding 12,000 feet. 



It is sufficiently clear that to generalize from the conditions of structure 

 observed along the line from central Ohio across southern Pennsylvania, 

 without careful consideration of the conditions both north and south 

 from that line would be dangerous, as liable to lead to serious error. 



Anthracite of Arkansas. 



Variation in proportion of volatile combustible matter, such as is ob- 

 served in Pennsylvania, occurs in other regions. The one of most interest 

 in this connection is that of western Arkansas. 



The existence of anthracite or semi-anthracite in western Arkansas 

 was announced by Dr. D. D. Owen* thirty-five years ago in his descrip- 

 tion of the coal mine at Spadra, in Johnson county. Additional notes 

 respecting the coals of Johnson county were given in a later report ;t 

 but Dr. Owen's study of the coals was merel}^ such as could be made 

 during a preliminary reconnoissance, so that the relations of these beds 

 to those in counties further west or in the area immediately beyond, 

 within Indian territory, were not determined. 



The first distinct statement respecting the succession of the Coal Meas- 

 ures in western Arkansas was given by Mr Winslow.t He found about 

 3,750 feet of measures, which he separates into three divisions : 



The Western or Upper Coal-bearing Division, consisting of sandstone 

 a;i(l shale 3,000 feet. 



The Intermediate Barren Division, consisting of shale and sandstone. . . 500 feet. 



The Eastern or Lower Coal-bearing Division, consisting of dark fissile 

 shale 250 feet. 



* <Jwen : First Report of a Geological Reconnaissanoe of the northern Counties of Arkansas, 

 1858, p. 130 etseq. 



fOwen : Second Report of a Geological Reconnaissance of the middle and southern Counties of 

 Arkansas, 1860, pp. 84-85. 



X Annual Report of the Geological Survey of Arkansas for 1888, vol. iii. The Geology of the Coal 

 Regions, by Arthur Winslow, pp. 10-26. 



