500 



EFFECTS OF TRAPPEAN INJECTIONS AMID THE COAL BEDS. 



containing white crystallized carbonate of lime, quartz, and sulphate of barytes are also frequent. 

 To a certain distance from the edges of this hill, the coal measures are of bad quality and much 

 dislocated ; but to the south-east, where no trap appears, there is a large tract of coal, which in 

 the miner's language is supposed to be " in the sound." This is the tract which has been recently 

 worked to the west of the great Brockmoor fault. 



The intrusive character of the trap of Barrow Hill is further proved, by the irregular form in 

 which the volcanic matter extends to the north-east by Cooper's Bank, which re- appearing here and 

 there in hummocks, beyond the high road from Himley to Dudley, renders a considerable tract 

 profitless. It is also prolonged in a narrow tongue, for nearly half a mile to the north-west, on 

 the sides of the little brook which flows from Himley Wood, where it may be seen cutting out 

 and dislocating the coal measures. (See right hand of wood-cut below) . But besides these courses, 

 which, for the most part, are apparent at the surface, this trap or "green rock" has been pro- 

 jected subterraneously in a tabular mass, nearly conformable to the coal measures, thus : 



The band e represents the greenstone, which having occupied the place of the heathen coal below the great coal, is 

 seen at different levels, (the effect of faults b, c, d), wedging out to the N.W. The dotted black band, above the green- 

 stone, indicates the thick coal in a coked or altered state. To the left hand or S.E. of a great line of fault (a), both 

 the thick coal and the heathen coal lie in regular positions and are wrcaltered, no trap rock having been there intruded amid 

 the strata. 



Here the trap is, for the most part, an amygdaloidal greenstone, containing kernels of white cal- 

 careous spar. Several shafts having been sunk through it, prove that this lateral spur of greenstone 

 occupies the place of the " Heathen coal." It is also ascertained to be wedge-shaped, being twelve 

 yards thick in the shaft nearest to Barrow Hill, and diminishing to two yards in that which is furthest 

 from it. The effect produced upon the coal measures into which this trap has been injected is most 

 remarkable. Not only is the" Heathen coal" entirely cut out and replaced by the greenstone, but 

 the thick coal lying some yards above it, is so altered as to be entirely worthless, being in that 

 coked condition which the workmen call " black and grizzly," i. e. the bitumen is driven off and the 

 mass is of a dull black colour, and much fractured ; burning to a red earth or ash, and giving out 

 little or no heat. 



The shafts are sunk through the greenstone for the extraction of the "white ironstone" which 

 lies beneath it, (marked by the lower line of dots) and that ore, so far from being deteriorated by 

 the proximity of the trap, is of superior quality. The trap, however, is not in absolute contact with 

 the ironstone, being separated from it by three or four yards of measures, including two or three 

 feet of coal, which, to use the miner's term, is in a " rocky" or indurated state. This tabular 

 wedge of trap has, therefore, clearly been subjected to fractures subsequent to its insertion amid 

 the strata, and to these faults I shall allude hereafter 1 . 



1 I am indebted to Mr. Timmins, the intelligent manager of these works, for the information concerning the 



