the Coal-fields of Pennsylvania. 411 



In the bituminous coal-measures west of the Alleghany 

 Mountains, the whole number of workable seams is less than 

 one half of that above named, as belonging to the anthracite 

 formation, while, including the thinner and less persistent 

 beds, the entire series cannot there amount to more than 

 eighteen or twenty. That portion of this great Appalachian 

 coal-field, which lies within Ohio, appears to possess even 

 somewhat fewer than the eastern half in Pennsylvania, the 

 beds suitable for mining being estimated at seven, and the 

 small seams about ten, in addition. 



Advancing westward to the great coal basin of Indiana and 

 Illinois, the coals thick enough for working are counted at 

 only six, and the thin ones proportionately few ; and this re- 

 markable progressive reduction in the coal-beds, going west- 

 ward, seems to be maintained as far as we advance in the 

 formation ; for crossing the Mississippi to the wide shallow 

 coal-measures of Missouri and Iowa, the number of the work- 

 able beds there believed to exist, does not amount to more 

 than three or four. Accompanying this interesting gradation 

 in the amount of coal, there occurs an equally noteworthy 

 diminution in the thickness and coarseness of the associated 

 strata, showing a progressive thinning down of the whole of 

 the land-derived coal-bearing portions of the carboniferous 

 deposits. A future comparison of the fossil plants of these 

 broad successive coal basins will probably disclose a corres- 

 ponding reduction in the number and variety of the species, 

 a view already suggested by their relative paucity in the bitu- 

 minous coal-fields of western Pennsylvania and Ohio, as mea- 

 sured by their abundance in the anthracitic basins. 



Wherever I have studied either of the anthracite fields, of the 

 great Appalachian basin, I have remarked that the lower or 

 "white ash" division of the coal-measures, gives indications 

 of more violent and frequent disturbances of level in the sur- 

 face, at the time of the deposition of the strata, than are 

 noticeable in the composition of the upper or "red ash" part 

 of the formation. Among the proofs are, more abrupt and 



