UPPER COAL MEASURES AND 10 YARD COAL. 



469 



Hill and Corngreaves to Hales Owen. At the Rag Mill, on the banks of the little 

 stream near Corngreaves, a vertical cliff of 30 to 40 feet exposes in descending order 

 the following strata. 



1. Coarse conglomerate of flattish and slightly rounded pebbles of quartz, compact felspar, and various trap rocks, varying 

 in size from a child's head to a bean, and imbedded in a greenish grey matrix of trappean detritus with fragments of green 

 earth. 



2. Mottled, dark red and dingy yellow, marly, granular, softish grit, occasionally passing into concretions of red marl or 

 clay. 



3. Dingy gi-een rock or volcanic grit (the blue rock of the workmen) made up principally of scoriaceous matter. It is 

 regularly iiiterstratified in beds varying from 8 to 12 feet, but like all depositary strata in this tract, it so wedges out, that 

 some shaft sections pass through a much greater number of beds of it than others. 



I shall return to the consideration of the origin of this deposit in the next chapter, 

 having here merely described its composition and connection with the other stratified 

 deposits which overlie the coal. 



Upper Coal Measures and 10 yard Coal. — In a district so much covered with loose 

 detritus, and in which the records of different shaft sections are full of discrepancies, 

 depending sometimes on natural distinctions, such as the thinning out of one stratum 

 and the setting on of another, but often upon inaccurate data, it is useless to record all 

 the details. Such only, therefore, as I think can he depended on, and may serve to 

 establish general views, are brought forward 1 . 



Owing to the great disturbances to which that part of the field which contains the 

 " ten yard coal" has been subjected, whether by the upheaval of the Silurian or trap 

 rocks, or by great dislocations both longitudinal and transverse of which we shall treat 

 hereafter, the same measures are reached at very various levels in different localities. 

 Thus, in some situations, shafts are sunk through shale and chinch with bands of sand- 

 stone, to depths exceeding 100 yards, before traces of coal are met with ; while in many 

 collieries, as near Wednesbury, all the overlying seams of coal and coal-smut which con- 

 nect the coal measures with the Lower New Red Sandstone, have been removed or have 

 thinned out, and the ten yard coal rises at once to the surface. It was this natural 

 outcrop of the thick coal which led our ancestors to work it in open quarries. As soon 

 as these day works were exhausted, shafts were sunk where the strata dipped beneath 



1 Since these chapters were written, an useful, small work (explaining the method of working coal mines), 

 has been published, entitled the Miner's Guide, by Mr. Thomas Smith. The reader will find that the details 

 of every shaft section therein, differ from those I have collected, thus adding strength to the argument founded 

 on the variety of composition of the strata in different parts of the field. At Highfields near Bilston, for ex- 

 ample, the " flying reed " is stated to be sixty-eight yards above the " ten yard coal," while at Deepfield, also 

 near that place, the same coals are separated by twenty-eight yards only of measures. Mr. Smith also gives a 

 section of unsuccessful boring through the Red Sandstone at Smethwick, to a depth of 187 yards. 



This author does not attempt to point out the order of superposition of the fundamental rocks. He talks, for 

 instance, of the Dudley limestone as mountain limestone, and describes the concretions of the Sedgely limestone 

 as having been rounded by attrition, so as to form a conglomerate ; and further, considering this field a basin, 

 he states that its old limits being marked by nature, will not be found to extend beyond its present boundaries ! 



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