0^ T THE FORMATION OF COAL-SEAMS. 



671 



46. IS^otes on the Formation of Coal-seams, as suggested by evidence 

 collected chiefly in the Leicestershire and South Derbyshire 

 Coal-eields. By "W. S. Greslet, Esq., F.Gr.S. (Read June 

 23, 1887.) 



[Abridged.] 



My principal object in this paper is to bring forward evidence in 

 opposition to the view now generally accepted that coal-seams 

 were formed from vegetation which grew on the spot. 



It seems to me that the growth-in-situ theory has been, or is still, 

 held by the majority of those who have considered or written upon 

 the question to be the right one, partly because the accumulation of 

 the vegetable matter of coal-beds by driftage appears to be totally 

 beyond our comprehension, and partly (probably chiefly) because we 

 have been told and led to believe that the underclays of coal-seams 

 contain the Stigmarice which were the very roots of the trees the 

 remains of which constitute the bulk of the coal. 



During an extensive experience in the midland district in connexion 

 not only with coal-mining, but also with the working of the underbeds, 

 the fireclays, both underground and in opencast workings, I have 

 had unusual opportunities of studying the relationship of the coal- 

 seams to the underbeds, their fossil contents, &c. 



The various points for consideration may be taken as under : — 



a. The relation of the fireclays to the coal-seams. 



b. ALode of occurrence of Stigmaria in underbeds. ' 



c. Erect fossil tree-stems with attached roots. - 



d. Lamination of coal-beds. 



e. The presence of boulders &c. in the underclays. 

 /. The foreign bodies in coal-beds. 



g. Marine fossils associated with coal-seams, brine, &c. 



a. It must not be concluded, because almost every coal-seam 

 rests upon a stratum partaking more or less of the nature of a fire- 

 clay and enclosing Stigmarice and other root-like fossils, that such 

 beds do not occur in other positions in the coal-measures ; for the fact 

 is that they very frequently occur lying immediately on the top of a 

 coal-seam, sometimes wholly removed from coal ; or they may occur 

 as very thin layers, often very irregular and locally distributed, 

 entirely enveloped in the coal. The thickness of an underclay bears 

 no proportion whatever to that of the coal-seam resting upon it. 

 The thickest coal-beds often rest upon the thinnest clays, and the 

 greatest development of fireclay will be followed by the most meagre 

 of coal-seams. I have also found it to be almost invariably the case 

 that where underclays come in contact with coal-seams there is a 

 sharp dividing line, a true bedding-plane, between the two ; we do 

 not find the clay gradually changing upwards into coal, but the 

 change from one to the other is most distinct, in fact the plane of 

 stratification is often quite a smooth one. Precisely the same cha- 

 racteristic obtains in the case of laminae of clay running through the 

 body of a coal-seam, i. e. where coal and clay are interstratified. 



