W. 8. Gresley— Coal Plants. 539' 



with in or upon (very rarely in) a coal-bed grew where they now 

 are ; but if a case of growth in place in coal has been or can be 

 established, notwithstanding the substance of the fossil is rock or 

 shale, nobody will dispute that the tree or the plant, whatever it 

 was, did contribute some coaly material to the coal-bed in which it 

 flourished. Be this as it may, the object of this paper is to record 

 the occurrence of forms or fossils composed of coal in actual contact 

 with beds of coal, that unquestionably were plants that grew 

 absolutely in situ, and thus to establish the fact that some coal-seams, 

 and typical ones too, are partly, at any rate, composed of vegetal 

 remains that have lived and died exactly on the spots now occupied 

 by them, I also want to make it quite evident that the forms to 

 which special reference is here made grew under water. 



:. Coal. 

 - Fireclay. 



Black shale. 

 A' Coal. 



D. 



Fig. 1. — Section of Coal and Clay-slate. 



The coal-seam A, Fig. 1 (the uppermost few inches of which 

 appear), is about 6 feet thick : it is overlain by a layer of black, 

 tough shale (called 'bone'), B, which is about 2 inches thick. 

 Over this 'bone' comes 10 to 11 inches of mottled fireclay, C, and 

 the clay is followed by strata of coal and shale for several feet. 

 These alternations of Coal-measures (Carboniferous), with trifling, 

 local differences, obtain for a very large portion of the area of the 

 seam, which is the ' Pittsburg' bed in S.W. Pennsylvania. 



An examination of the horizon A- A' — the top of the seam of 

 coal proper — reveals the phenomenon of the bright, brittle, pitch- 

 like coal lamina, sending out, or more properly, having developed, 

 upward swellings, expansions, and horn-like processes D, not only 

 into the black shale B, but also into the clay C, and in those two 

 strata dividing, branching, curving, and expanding in a peculiar 

 but uniformly characteristic manner. Tliis phenomenon is a very 

 common one ; and since these coaly forms extend very much farther 

 horizontally than vertically, and possess their limbs, lobes, expansions, 

 branches, leaves, or whatever their parts or processes should b© 

 called, in ever varying shape, position, and trend, any section or 

 exposure of them shows change and difference in form. In some 

 places they appear in great profusion, in others are scattered or of 

 less development and therefore less conspicuous. As to chemical 

 composition and physical aspect, these strange meandering forms in 

 the top of the coal-seam differ but little, if at all, from the black brittle 



