448 



ORIGIN OF THK AI'PAI.ACIUAX Ct)AL STUATA, 



twelve feet. Still further to the west, between the Monongahela 

 river at Brownsville and the Ohio at Wheeling, it declines from 

 about ten to eight feet, and beyond this, in the state of Ohio, it 

 seldom exceeds five or six feet. Following it longitudinally, or 

 in the direction of the great elliptical basin, it displays quite as 

 remarkable a persistency in its dimensions, the reduction in its 

 size being, if any thing, still more gradual from northeast to south- 

 west. Thus at Pitlsburg it measures, altogether, about eight feet ; 

 at the mouth of Big Grave creek rather more than five ; on the 

 Great Kenawha about five ; and from this point to Guyandotte, 

 where it terminates, three feet; and, finally, hardly two feet. 

 Tracing it along a parallel line, from northeast to southwest, but 

 nearer its southeastern outcrop, we detect the same very gi-adual 

 abatement in its thickness. While we are thus furnished with 

 conclusive evidence, from the fact that its rate of increase is most 

 rapid towards the southeast, that the ancient land with which the 

 stratum was connected must have been situated in that du-ection, 

 we see that the northeastern part of the coast was the quarter 

 where its materials were supplied in the greatest abundance. To 

 this conclusion I am disposed to appeal, 'in support of the conjec- 

 ture already ventured, that this great bed of the main or western 

 coal-field, is but a remnant of a still more expanded stratum, 

 which attained its maximum size, in the enormous seam of which 

 all the anthracite basins present us insulated patches. The sin- 

 gular constancy in the thickness of this' Pittsburg bed, no less 

 than its prodigious range, are circumstances that seem strongly 

 adverse to the theory which ascribes the formation of such de- 

 posits to any species of drifting action. But a more tliorough 

 discussion of this question will be attempted presently. 



Of the INTIMATE Mechamcal Structlre of the Coal. 



An examination of the stracture of the coal itself, apart from the 

 fact of the great range and uniformity in the thickness of the 

 beds, renders it apparent, that no iiTcgulai- dispersion of the vege- 

 table matter by any conceivable mode of drifting, either into 

 estuEiries, or the open sea, could produce the phenomena which 



