BITUMINOUS AND ANTHRACITIC. 449 



they exhibit. The mechanical arrangement of the layers in ev- 

 ery coal seam, as seen when viewed edgewise, indicates plainly, 

 that it is a compound stratum, as much as any other sedimentary 

 deposit, each bed being made up of innumerable very thin lami- 

 na3 of glossy coal, alternating with equally minute plates of im- 

 pure coal, containing a small admixture of finely divided earthy 

 matter. These subdivisions, differing in their lustre and fracture, 

 are frequently of excessive thinness, the less brilliant leaves some- 

 times not exceeding the thickness of a sheet of paper. In many 

 of the purer coal-beds, both anthracitic and bituminous, these thin 

 partings between the more lustrous layers, consist of little laminae 

 of pure fibrous charcoal, in which we may discover the peculiar 

 textm-e of the leaves, fronds, and even the bark of the plants which 

 supplied a part of the vegetable matter of the bed. If traced out 

 to their edges, all these ultimate divisions of a mass of coal will 

 be found to extend over a surprisingly large surface, when we 

 consider their minute thickness. Pursuing any given brilliant 

 layer, whose thickness may not exceed the fourth part of an 

 inch, we may observe it to extend over a superficial space which 

 is wholly incompatible with the idea, that it can have been de- 

 rived from the flattened ti-unk or limb of any arborescent plant, 

 however compressible. When a very large block of coal is thus 

 minutely and carefully dissected, it very seldom, if ever, gives 

 the slightest evidence of having been produced from the more 

 solid parts of trees, though it may abound in fragments of their 

 fronds and deciduous extremities. The laminae of brilliant car- 

 bonaceous matter almost invariably thin away to a fine edge be- 

 fore they terminate, a fact which of itself seems to prove, that the 

 material was in a soft or pulpy state at the time of its accumula- 

 tion, and this supposition receives countenance from the homo- 

 geneous texture and conchoidal fracture of every such layer. 



Granting the con-ectness of this inference, which is not in conflict 

 with the beautiful microscopic determinations, by Hutton, respect- 

 ing the traces of vegetable structure in certain portions of coal, the 

 argument seems almost conclusive, that the vegetable matter gi-ew 

 where it was deposited. It is difficult to understand why the 

 coal should not consist, principally, of the larger parts of trees, 



