§ 7. MODE OF DEPOSITION OF THE COAL. 669 



Upon this is deposited the coal ; a bituminous mass of 

 coniferous wood, gigantic ferns, club-mosses, &c. as we 

 shall presently demonstrate ; occasionally stems of trees are 

 found passing vertically through this bed. 



In the third place, we have a deposit of drifted materials 

 promiscuously intermingled with the foliage and stems of 

 numerous kinds of terrestrial plants ; the whole appearing 

 to have been subjected to the mechanical action of floods 

 of water. 



These facts seem to indicate that a bed of coal of this 

 kind, is nothing more than a submerged forest. The 

 under -clay may have been the natural soil in which the 

 Stigmariae, the roots of the trees forming the coal above, 

 originally grew ; the coal, the carbonized stems and foliage 

 of the trees to which the roots belonged ; and the upper 

 stratum or roof, may have resulted from detritus transported 

 from a distance by a debacle or flood, which overwhelmed 

 and buried the foliage and stems of the prostrate forest. 



These phenomena may be explained by supposing that a 

 plain, densely clothed with vegetation, was inundated by an 

 irruption of the sea ; or overwhelmed by a flood of water 

 from an inland lake, occasioned by the sudden removal of 

 some barrier ; or by the subsidence of the tract of coun- 

 try on which the forest grew. But when we find an unin- 

 terrupted series, in which triple deposits of this kind are 

 repeated thirty or forty times, and through a thickness 

 of several thousand feet, this solution of the problem, though 

 very plausible, cannot, I apprehend, be deemed conclusive. 

 Not only subsidence after subsidence must have taken place, 

 but the first submergence have been followed by an elevation 

 of the land ; and then another soil capable of affording sup- 

 port to a second forest must have been produced, and another 

 generation of vegetables, of the same species as the former, 



mariae. In the Appalachian coal-field of the United States, the same 

 phenomenon appears. 



