THE BREIDDEN HILLS— MOEL-Y-GOLFA, ETC. 



291 



country. Thus their outline, as seen from the north and north-east, is expressed in the 

 opposite sketch, in which the Moel-y-Golfa and its dependencies constitute a separate 

 undulating ridge, diminishing in height as it advances to the north-east; while the 

 Rodney Pillar, or the true Breidden, appears as one heavy mass. Again, if viewed 

 from the south-west, Moel-y-Golfa appears like Vesuvius, while the Criggan and Breidden 

 form two other distinct conical ridges. (See Drawing prefixed to ensuing chapter.) 



The general relations of these hills are similar to those of some of the ridges already 

 described. They exhibit (though rarely) indications of contemporaneous trap, alter- 

 nating conformably with beds of sedimentary origin, as in the Shelve country. The 

 chief rock, however, is of intrusive origin and has been forced through previously formed 

 Silurian strata, masses of which are either inclosed between the ridges of trap, or thrown 

 off by it in vertical and dislocated patches. 



The prevailing mass in the Breidden properly so called (Rodney Pillar Hill), is a coarse-grained 

 greenstone, arranged (near the summit) in rude columnar masses, as expressed in the vignette, p. 287. 

 On the south-western and most precipitous face of this hill overhanging the Severn, the greenstone 

 is porphyritic, and passes into small concretionary and fine granular felspar rocks, with disseminated 

 carbonate of lime. In some places it assumes the characters of clinkstone, and in others it is an 

 amygdaloid, containing kernels of calcareous spar. The colours vary from dark green to light grey 

 and blue : one of the small concretionary varieties (green with white spots), protrudes in a small boss 

 beyond the north-east termination of the Breidden, at a spot called Belem bank close to the Severn, 

 and from its hardness has been long quarried for the Shrewsbury roads. This mass of trap, about 

 100 feet in height, forms, like that of Welchpool, a great dyke exposed to a width of about eighty 

 paces. In parts the trap divides into coarse columns, inclined at an angle of 40°, and the faces of 

 the fissures or joints are covered with matter coloured green by chlorite. The rock itself is fine 

 granular felspar, tending to a small concretionary structure. It is partly amygdaloidal and cellular, 

 and is occasionally traversed by veins. The Voel, a round, detached hillock, at the south-western 

 or opposite extremity, is a coarse-grained greenstone. The Breidden itself, having upon three sides 

 precipitous faces which rise abruptly from the flat vale of the Severn, offers few clear evidences of 

 association with the stratified deposits, except upon its east and south-south-eastern or hilly side, 

 where dislocated and broken patches of shale adhere to the trap. The Criggan exhibits several 

 knots of trap in forms more or less columnar \ at the New piece, the trap pierces the sandy shale, 

 the beds of which are vertical, fractured, and in parts converted into a silicified slate. The most 

 instructive instance of the ancient or bedded trap analogous to those cases described in the Shelve 

 and Corndon districts, is at Bauseley Hill near the east-north-eastern termination of the ridge. The 

 centre of the trap is laid open by extensive quarries, and it consists chiefly of a large concretionary 

 felspar rock, in parts porphyritic, which is flanked on the north-west by a vertical wall of sandy 

 greenish schist, slightly micaceous, with little or no appearance of having been altered. This is fol- 

 lowed by a thin course of greyish-blue, granular felspar rock, succeeded by finely laminated, soft 

 shivery, black shale, perfectly unaltered. The shale is again followed by bands of felspathic trap, 

 partly porphyritic and passing into greenstone. They are about four yards thick, and flanked by 

 a trappean aggregate, containing fragments of schist, and casts of fossils precisely like those described 

 in the Shelve country. It is from twenty-five to thirty feet thick, regularly bedded, and towards 

 the exterior passes into a greenish-grey sandstone, evidently formed of volcanic submarine dejections. 



