506 TRANSVERSE FRACTURES POSTERIOR TO TRAP INTRUSIONS. 



the cross fractures in this coal-field seem to afford a good illustration of a portion of 

 the ingenious reasoning of that gentleman ; for whilst the Lanesfield and Birch Hill 

 faults are nearly at right angles to the north-east and south-west strike of the strata 

 which they traverse, so are the Pouk Hill and other faults transverse to the other axis, 

 which in the southern district trends from Dudley on the N.N.W. to the Lickey quartz 

 rock on the S.S.E. In fact, these cross fractures are varied exhibitions of the same 

 phenomena, which in previous chapters were described as having produced the trans- 

 verse valleys of dislocation. 



One of the most important of the faults cuts off the 10 yard coal-field to the south 

 of Corngreaves, and brings it abruptly into contact with the Lower New Red Sandstone. 

 This, which may be called the " Corngreaves fault," is undeniably more worthy of 

 attention than any other east and west fracture ; for the 1 0 yard coal has recently been 

 proved to range up to it in undiminished thickness and of excellent quality. Hence, 

 there is every reason to believe that the productive coal-field will be hereafter worked 

 beneath that portion of the tract, marked Lower New Red Sandstone in the map, which 

 extends from Hales Owen to Old Swinford. (Lord Lyttelton's country 1 .) 



All the great transverse faults of this field with which I am acquainted, must have 

 been produced after the insertion of the trap rocks amid the carboniferous strata. This 

 is proved, by finding certain masses of greenstone, which have been shifted up and 

 down with the coal and iron beds; so that the ends of any one of these masses, instead 

 of being continuous with other portions of trap, abut abruptly against coal measures, 

 and when thus lost, are found again at a different level but having the same relative 

 position in the strata. This has been already shown on the western side of Barrow 

 Hill, where a wedge of greenstone having been inserted amid the coal measures and 

 having entirely charred the coal, the whole mass has been subsequently broken up by 

 transverse faults as in the diagram, p. 500. 



Another clear example of this phenomenon occurs on the eastern slope of the Birch 

 Hill Collieries, whence a double line of fissure proceeds in a somewhat zig-zag line by 

 Bentley Lodge to Pool Hays. On the outside of the most southern of these fissures 

 " the blue flats" or bottom beds of the field are thrown up to near the surface, without 

 any cover of trap; whilst to the north of it, the same bed of ironstone has been worked 

 at the depth of 180 yards, the shafts passing through a mass of greenstone immediately 

 above the bottom coal. The measures there occupy a trough of upwards of 100 yards in 

 width, and lie in nearly a horizontal position, when they are met by the second line of 

 fissure, and the whole of these are upcast from 40 to 50 yards, the mass of greenstone 

 being shifted into the same relative place between the 4 foot and the bottom coal which 

 it occupies in the lower trough. 



1 I shall most sincerely rejoice if this anticipation is realized, and that the family of the late Lord Lyttelton 

 should benefit by the hint of one, who cherishes a grateful recollection of the pleasant days spent at Hagley 

 Park, in the company of that highly accomplished nobleman. 



