CHAPTER XXVI. 

 TRAP AND ALTERED ROCKS OF RADNORSHIRE {continued.) 



Group of Llandegley, Llandrindod, and Carneddau near Builth. Mineral Waters 

 of these Tracts.— (PL 33, figs. 3, 4, 5, 6 & 7. See also Map and opposite 

 sketch of the southern end of Carneddau, near Builth.) 



THE largest trap district of Radnorshire extends from Llandegley and Llanbadarn-fawr 

 on the north-east and north, to the environs of Builth on the south-west. Its extreme 

 length from Llandegley Wells to the Park Wells near Builth is nearly ten miles, and 

 the greatest breadth from Blaen Eddw and Bettws Disserth to Cefn Lys and Llandrindod 

 Common, is upwards of five miles. From Llandegley to Builth, the main ridges of 

 trap are the Llandegley rocks, Sunny-bank, Gelli, and the Carneddau. Besides these, 

 a great embranchment is thrown out on the north-west by Carreg-gwiber and Cwm- 

 brith Hill to Cefn Llys, and the hillocks north of Llandrindod Wells. On the eastern 

 or south-eastern flank of the main ridge, and running parallel to it, are a number of 

 smaller, elongated mounds of trap, having the same direction, from Blaen-Eddw and 

 Llandegley Rhos on the north-east, to Llansaintfraed and Llwyn-Madock on the south- 

 west. Many of these trap ridges inclose longitudinal valleys, excavated in the lower 

 Silurian shale and flag, the beds being tilted in divergent directions upon the opposite 

 sides of the intrusive rocks, and changes in the mineral character of the deposits are 

 usually visible at the points of contact. The same phenomenon is also seen at some 

 places on the north-western face of the chain, between the Gelli and the banks of the 

 Ithon near Llandrindod ; the most instructive example being perhaps that between 

 Gwern-y-fad and Builth, on the banks of the Wye. In addition to these intrusive rocks, 

 amid some of which the strata are thrown into lofty hills, are distinctly stratified traps, 

 alternating with beds of marine sediment. 



This district, therefore, is precisely similar in its relations to the tract of Shelve and 

 Corndon, previously described • and it is made up of similar ridges, and deeply trenched 

 narrow valleys, running from north-east to south-west 1 . Great portions of the surface 

 are arid and barren, particularly the sloping banks, moors and commons near Llan- 

 degley and Llandrindod. This sterility is perhaps greatest, where the soil consists en- 



1 This tract is as impassable and little visited as that of Corndon and Shelve, Shropshire. 



