450 ORIGIN OF THE APrALACHIAN COAL STRATA, 



such as their trunks, limbs, and roots, if any species of drifting 

 operation brought together the materials of the bed, by conveying 

 seawards the growth of ancient forests. The leaves, and other 

 fragile parts, would soon become detached on the voyage, and 

 these, together with the smaller plants, would subside and get 

 imbedded, long before the trunks and lighter woody parts could 

 grow sufficiently water-logged to sink. It is obvious, that a 

 stratum formed by the successive deposition of huge in'cgular 

 stems and branches, would exhibit, no matter what might be the 

 subsequent pressure, a very different structure from that thin and 

 uniform lamination, which distinguishes all beds of coal. These 

 considerations, derived from the mechanical features of every seam 

 of coal, receive strong confirmation from the microscopic research- 

 es of Mr. Hutton. Though that observer found more or less of 

 the cellular vegetable structure in each of the three varieties of 

 Newcastle coal, he discovered a complete obliteration of the char- 

 acteristic cells in those finest lustrous portions of the caking coal, 

 where the crystalline structure, as he terms it, is best developed. 

 Besides the above-mentioned featm^es, all the coal-beds which I 

 have ever examined or seen minutely described, possess another 

 peculiarity in their mechanical constitution, on a less minute 

 scale, which is equally incompatible with the notion of a trans- 

 portation by currents. I refer here to the subordinate divisions 

 of the coal-beds, some of which are strata of pure coal, some 

 of earthy coal, and some of common shale, all constituting 

 together the compound mass, which we call a coal-seam, but each 

 maintaining its particular position and character as a distinct de- 

 posit over an area which is truly astonishing. Those persons 

 who are conversant with large mining districts are aware of the 

 many instances of remarkable persistency in these subdivisions 

 in the coal-beds, since it is frequently by their means that the 

 miners recognize a known coal-seam in cases of difficulty. 

 Thus the largest bod of the anthracite fields of Pennsylvania 

 contains, almost every where, a particular band of unusually pure 

 coal, not far from the bottom, generally from three to four feet in 

 thickness. A still more strilving example occurs in the great 

 Pittsburg bed, already spoken of. If we dissect this compound 



