45G ORIGIN OF THE APPALACHIAN COAL STRATA, 



of one uniform material, almost invariably present, composed of 

 finely divided particles, the beds overlying the coal consist of 

 nearly every variety of rock embraced in the formation, though 

 they are more usually some form of laminated carbonaceous 

 slate. Both in composition and structure, the roof rock manifests 

 signs of having been deposited by a more or less rapid cuiTent. 

 In place of a single species of fossil plant, it usually includes a 

 prodigious variety, and the delicate ramifications of these, instead 

 of intersecting the bed in various directions, as the processes of 

 the Stigmaria do in the fire-clay, lie in a singularly disordered 

 and fragmentary condition, in planes almost invariably parallel 

 to the bedding. Lindlcy and Hutton, in their work on the Fossil 

 Flora of Great Britain, give the following very accurate descrip- 

 tion of the mode in which the organic remains occur in the roof 

 slates in England, and the account is equally applicable to those 

 of the United States : — "It is the beds of shale or argillaceous 

 schistus, which afford the most abundant supply of these curious 

 relics of a former world ; the fine particles of which they are com- 

 posed having sealed up and retained in wonderful perfection and 

 beauty the most delicate forms of the vegetable organic structure. 

 Where shale forms the roof of the workable seams of coal, as it 

 generally does, we have the most abundant display of fossils. 

 The principal deposit is not in immediate contact with the coal, 

 but from twelve to twenty inches above it, and such is the im- 

 mense profusion in this situation, that they are not unfrequently 

 the cause of very serious accidents, by brealdng the adhesion of 

 the shale-bed, and causing it to separate and fall, when, by the 

 operation of the miner, the coal, which supported it, is removed. 

 After an extensive fall of this kind has taken place, it is a curious 

 sight to see the mine, covered with these vegetable forms, some 

 of them of great beauty and delicacy ; and the observer cannot 

 fail to he struck with the extraordinary confusion, and the nume- 

 rous marks of strong mechanical action, exhibited by their broken 

 and disjointed remains^ Such is the nature of the roof, when it 

 consists of the usual carbonaceous shale or slate, but it is of- 

 tentimes a much coarser rock in the Appalachian coal-fields ; 

 being either an argillaceous flaggy sandstone, or a coarse arena- 



