Border Country of Salop and North Wales ; Sgc. 243 



shalcj which has been mentioned as lying- beneath the limestone at Llansilin ; 

 but sometimes a crystalhne siliceous deposition occurs^ and at intervals unstra- 

 tified masses of trap present themselves. These, together with the remains 

 of organic bodies, will claim our chief attention. 



An example of the siliceous deposition is seen to advantag-e in the park near 

 Powis Castle in the immediate vicinity of Welchpool. It occurs in strata dip- 

 ping towards the north-west at an angle varying from 45° to 70°, and forms 

 a long ridge with an abrupt escarpment. The strata are not separated by 

 planes, but have a waved and svvelling superficies. When broken, they divide 

 into pieces having sharp edges and angles, and triangular or trapezoidal sur- 

 faces. In many places the rock becomes very red ; in others it is little or not 

 at all coloured with iron ; masses and thin beds of clay are found among the 

 strata. From the clayey and ferruginous portions the soil of the park is pro- 

 bably derived ; it is fertile, and abounds with fine trees : these circumstances 

 all show the identity of this rock with that so often noticed at Bromsgrove 

 Lickey near Birmingham ; in this, however, the imbedded grains of sand are 

 larger than in the Lickey quartz-rock. At both these places the siliceous 

 rock contains impressions of the various shells, corals, &c. which are found in 

 the limestone. In some cases the cavities so impressed have been filled again 

 by a subsequent deposition of calcareous spar, which also forms veins in the 

 rock and entirely penetrates its substance. 



Half a mile from Welchpool on the west of that town are large quarries of 

 greenstone worked in the side of an eminence called Standard Hill. The 

 principal cleavages of the rock are nearly vertical in parallel planes 10 or 12 

 yards asunder. By other cleavages, subordinate to these and perpendicular 

 to their planes, it is divided into columns, which lie in a nearly horizontal 

 position and approach to regular prismatic figures. The colour of the rock is 

 in general a light green, sometimes marked with white specks ; it contains 

 small portions of anthracite and carbonate of lime. In a part separated from 

 the rest only by one of the great vertical cleavages, it approaches much nearer 

 to the usual appearance of the trap rocks of Great Britain, being harder, of a 

 dark colour, and containing disseminated grains of iron pyrites. 



A grauwacke slate alternating with beds of shale, which forms the ridge of 

 Rallt at a little distance to the north, and great part of the long mountain on 

 the east, is found also at the base of Standard Hill ; between it and the green- 

 stone there occurs a dyke or large vein, consisting of rounded pebbles and 

 angular fragments of the contiguous rocks cemented by limestone ; each 

 pebble or fragment is surrounded by a coating of white calcareous spar : this 

 dyke of breccia is nearly vertical, and several yards in thickness. 



