470 



SUCCESSION OF STRATA IN THE 10 YARD COAL-FIELD. 



the surface, and the same thick coal was regained at depths, varying from one to two 

 hundred yards. In sinking these shafts, the miner soon perceived, that the coal mea- 

 sures generally succeeded each other in a given order. Thus, he found in descending, 

 that at a certain number of yards (more or less in different places) courses of smut and 

 poor coal, including the two foot seam, were interlaminated with shale and sand- 

 stone ; that passing through these strata, a bed of good coal occurred, from two to five 

 feet thick, and again penetrating through numerous other strata, in some places con- 

 taining an uncertain seam of coal (the flying reed or red) \ he reached the same thick 

 mass of coal which had been previously worked out at the surface. Again, in sink- 

 ing to greater depths, lower coal measures with iron stone were discovered. The 

 uppermost coal bed worthy of notice was termed the " broach coal," as being the index 

 by which the rich field was broached or tapped. In like manner a variable coal seam 

 which expanding and contracting (occurring at intervals only), received the name of 

 " flying reed." Now in most of these details we have little more than the ordinary ac- 

 companiments of other coal-fields ; for in previous chapters we have abundantly ex- 

 plained, how a stratum which is composed of sandstone in one part of a field, tapers 

 out and passes into clunch and shale at no great distance ; while coal beds deteriorating 

 in their course, become shale, and beds of shale (often in a very short horizontal dis- 

 tance), graduate into coal. (See pp. 101—102.) 



In consulting the sections, p. 477, the reader will find abundant proofs of these 

 conditions. Thus the " broach coal " occurs at very various depths. In one shaft, 

 it is separated from the great coal by a considerable thickness of measures, including 

 the "flying reed coal," while in another the "broach" and the "great coal" lie 

 within a few yards. These phenomena are, indeed, no longer subjects of surprise to 

 geologists, since they are explicable by reference to the natural operations by which 

 sand, gravel, mud and vegetable substances have been, and ever will be, accumulated, 

 under large lakes and seas. On this point I refer my reader to the general views con- 

 cerning the origin of coal-fields, p. 148. 



The prevailing succession of the coal strata in the central parts of the field, where 

 works had been long in existence, is given by Mr. Keir, and is copied from his letter 

 into Dr. Thomson's sketch, and thence into the Geology of England and Wales, p. 409. 

 These sections, however, referred merely to a limited tract, then known as the coal-field, 

 rigorously bounded as it was supposed by certain faults. I therefore annex other 

 sections of shafts more recently sunk in various parts of the field which establish the 



1 The Flying Reed, as described by Mr. Keir and Dr. Thomson, is where the two upper beds of the ten 

 yard coal separate from the chief mass; beds of shale, ironstone, &c, setting in between them for a thickness 

 sometimes of about twelve feet. In a section, however, at King Swinford furnished by Mr. Downing (No. 1. 

 table, p. 477.), the Flying Reed is separated from the thick coal by upwards of forty-two yards of measures ! ! 

 so little is a section taken from any one part of the field applicable to another. In this respect the field much 

 resembles that of Coalbrook Dale, (see p. 101.) 



