288 TRAP ROCKS OF MONTGOMERY, NANTCRIBBA AND WELCH POOL. 



thirty to forty feet in depth. The prevailing rock is greenish and purple felspar, partly concretion- 

 ary, passing into hard felspar porphyry, and rising through vertical, dislocated and contorted beds 

 of indurated sandstone. On one side I observed these beds dipping 80° north-north- east, as ex- 

 pressed in this wood- cut. 



N.N.E. 



s.s.w. 



46. 



a. Unaltered shale. 



i I - \ 

 i i i i 



c. Altered rock. 



d. Trap. 



Similar trap reappears at Stallow, two miles south-south-west of Nantcribba, where it is also 

 partially quarried, and half a mile further upon the same line is another outburst, forming the bold 

 precipitous rock on which stands the ancient Castle of Montgomery. On its northern face, which 

 is vertical and about eighty feet in height, this rock has been much quarried, not only as a road- 

 stone, but for coarse building purposes. The general colour of the rock is light-green, and the 

 predominating structure is concretionary, being composed, for the most part, of a fine granular 

 felspar, slightly porphyritic, with veins of white carbonate of lime, and occasionally minute nests 

 and flakes of anthracite ; it is split by many transverse fissures, and has some appearance of being 

 traversed by dykes. The sandstone and shale, in contact with the trap, are tilted and dislocated, 

 as seen on the bluff north-east and north-western faces. At the south end, but detached from the 

 trap, are highly inclined beds of sandstone flag containing Grcqjtolites. In the loftier and adjacent 

 hill of Fridd Baldwin, separated from the castle rock by a deep dingle, similar beds of flagstone are 

 nearly vertical and much contorted. These flagstones, dipping away to the west and north-west, 

 mark one of the flanks of the axis of elevation, due to the eruption of the trap of Montgomery 

 Castle, Stallow, and Nantcribba. Between the Nantcribba trap and Welch Pool, are undulating 

 hills of shale, but near the town on the left bank of the Severn is another outburst of trap. 



Trap of Welch Pool. 



47. 



View of the Standard Quarries, from a drawing by Lady Lucy Clive. 



