﻿Vol. 6 1 .] IN" THE NORTH-STAFFORDSHIRE COAL-MEASURES, 497 



(b) Identification and Correlation of Coal-Seams. 



Owing to the variation in the characters of coal-seams with 

 respect to thickness, quality of coal, nature of roof, and presence of 

 dirt-bands in the coal, the seam-nomenclature in all our coalfields, 

 when referred entirely to these characters, is more or less conflicting. 

 When these physical difficulties in correlation are artificially re- 

 inforced by the inducement to alter the name of a coal-seam for 

 commercial purposes, we may to some extent understand the existing 

 confusion. Nevertheless, without any aid from palaeontology, the 

 correlation of seams that has been accomplished by mining-engineers 

 is remarkably accurate. In some measure, this is due to the fact 

 that the coal-seam itself is a stratum which implies special conditions 

 of deposit, and, viewed in this aspect, affords evidence almost as 

 valuable as that of palaeontology for the purposes of stratigraphy. 

 All the work of correlation of seams has been left to the mining- 

 engineer, whose profession demands a much more detailed and exact 

 knowledge of the Coal-Measures than that obtainable from the groups 

 above mentioned, even could such groups be traced throughout 

 the coalfields. 



It seems, therefore, surprising that, for this work of identification 

 of coal-seams, the aid to be derived from marine bands should not 

 have been more fully utilized. In a series of measures which are 

 largely of terrestrial and freshwater origin, the presence of marine 

 bands denotes singularity of conditions of deposit, which constitutes 

 them ideal horizons for the purposes of stratigraphy. The dis- 

 similarity, between the freshwater and the marine mollusca most 

 commonly found fossil in the Coal-Measures, is so marked that they 

 can be readily distinguished by those totally ignorant of palaeontology. 

 Phillips long ago pointed out the peculiar interest of these beds, 

 and after describing the occurrence of one of them over an area 

 embracing the vicinities of Leeds, Bradford, Halifax, Penistone, and 

 Sheffield, stated that 



'The uniform occurrence of these pectens and ammonites [Pterinopecten and 

 Goniatites] through so wide a range, over one particular thin bed of coal . . . 

 is one of the most curious phenomena yet observed concerning the distribution 

 of organic remains, and will undoubtedly be found of the highest importance 

 in all inferences concerning the circumstances which attended the production 

 of coal.' l 



This line of research, however, has not been followed, and, 

 although in most of our coalfields marine beds have been found at 

 isolated localities, so far as the writer is aware no systematic effort 

 has been made to trace them throughout those coalfields. In fact, 

 their true significance in Coal-Measure stratigraphy seems to have 

 been misapprehended, or subordinated to that of the workable seams 

 of coal and ironstone. When these seams cease to be workable, by 

 pinching-out or otherwise deteriorating, it is not uncommon for 

 their names to be given to a different bed, which may occur about 



1 Encyclopaedia Metropolitana, vol. vi (1845) art. on Geology, p. 590. 

 Q. J. G. S. No. 243. 2 n 



