BITUMINOUS AND ANTHRACITIC. 473 



and comparatively wide apart ; but, even here, we observe a beau- 

 tiful progression in the amount of the bitumen, as we recede from 

 the very low axes which traverse the southeastern side of the great 

 plain. What renders the foregoing comparison of the several ■ 

 ranges of the coal-formation particularly exact and satisfactory 

 is, the circumstance, that, in more than one instance, we are enabled 

 to trace the very same coal-seam, through its various degrees of 

 bituminization, from an almost true anthracite, to a form in which 

 it possesses a full proportion of volatile matter. Thus the great 

 Pittsburg bed, to take it as an example, contains on the Potomac, 

 in some localities, as little as 15.5 per cent., but near the eastern 

 margin of the great western basin, as at Blairsville, and again in 

 Virginia, it has about thirty-one per cent, and towards the middle 

 of the main basin at Pittsburg and on the Kenawha, as much as 

 from forty to forty-three per cent. 



The cause of the difierent degrees of de-bituminization of the 

 coals, in different parts of their range, I am disposed to attiibute to 

 the prodigious quantity of intensely heated steam and gaseous 

 matter, emitted through the crust of the earth, by the almost infinite 

 number of cracks and crevices, which must have been produced 

 during the undulation and permanent bending of the strata. All 

 the phenomena of modern earthquakes and volcanos, warrant us in 

 supposing that the elevation of our coal rocks, if effected in the 

 manner I have imagined, must have been accompanied by the 

 escape of an immense amount of hot vapors, the chemical and 

 thermal agency of which cannot be overlooked, upon any hypoth- 

 esis of the rending and uplifting of great mountain tracts. It is 

 easy to conceive, that the coal, throughout all the eastern basins, if 

 thus effectually steamed, and raised in temperatm'e in every part 

 of its mass, would discharge a gi'cater or less proportion of its 

 bitumen and other volatile constituents, as the strata were more 

 or less frequently and violently undulated by earthquake action. 

 It is also obvious, that the more western beds, remoter from the 

 region of active movements, less crushed and fissured, and pre- 

 senting a greater resistance to permeation by the subterranean 

 vapors, would, in virtue of their mere geographical position in 

 the chain, be much less extensively de-bituminized. The striking 

 31 



