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CARADOC SANDSTONE IN RADNORSHIRE. 



masses of the rock, planes of stratification may be seen on most parts of the south-eastern face of 

 the cliff above the high road, dipping 60° to the east, and thus they may fairly be said to rise from 

 beneath the Lower Ludlow Shale of the adjoining valley of Knill. 



In one of the upper portions of this rock, where the unbedded character prevails, a cavern 1 of 

 about thirty feet by twenty-five was cut into a few years ago. (See letter o of preceding wood-cut.) 



From Woodfield to Old Radnor the limestone is again lost, but at the latter place it re-appears in 

 great force both on the north-western and south-eastern faces of a hill of trap, sometimes highly 

 altered and dislocated, as will hereafter be described. In other places, however, south of Old 

 Radnor, and at a certain distance from the trap rock, the limestone in its unaltered condition dips 

 gently to the north-west. It is there regularly bedded, grey, and subcrystalline, with way boards of 

 clay, and contains several Wenlock fossils, particularly corals. It passes under the dark-coloured 

 shale of the Vale of Radnor, which represents the Lower Ludlow Rock. Among the many absurd 

 trials for coal in this district, no one appears more inexplicable than the sinking through the shale 

 at this place. The slightest acquaintance with the stratification of rocks would prove, that the shale 

 in which the shaft was sunk rests distinctly upon the limestone. Such trials, therefore, if persevered 

 in, could only establish either the persistence or the thinning out of the limestone beneath this 

 shale. The discovery, however, of the subterranean continuance of this limestone would in itself 

 be valuable, since Old Radnor is the most south-westerly point where any large mass of limestone 

 has been detected in the whole range of the Upper Silurian Rocks of South Wales. It is conse- 

 quently transported to great distances, even sixty miles ; and although there is yet an enormous 

 unwrought mass of it in the Nash Scar and in the low hills south of Old Radnor, it is well to reflect 

 that if the same limestone is regained at a slight depth, which owing to the very gentle inclination 

 of the strata is highly probable, it may be profitably extracted when all the exposed portions shall 

 have been exhausted 2 . 



Lower Silurian Rocks in Radnorshire. 



The Lower Silurian Rocks are little developed near the eastern frontier of this county. 

 Some of their upper beds have been alluded to as forming the nucleus of Nash Hill near 

 Presteign. They there occur in arched, highly inclined, and vertical strata of hard 

 quartzose grits and fine conglomerates, rising from beneath the Wenlock limestone, and 

 throwing off unconformably on the opposite flank, ledges of Old Red Sandstone and 

 Ludlow rocks. Above Corton Gate they contain casts of some of the most characteristic 

 shells of the upper beds of the Caradoc sandstone, such as the Pentamerus oblong us and 

 P. Imvis. There are also traces of these rocks on the sides of the Old Radnor Hills. 

 The greatest mass of them emerges from the surrounding shale in the great trap district 

 of Llandegley, Llandrindod, and Builth, but whether consisting of Caradoc sandstones 



1 I did not examine this cavern, as the many heavy lumps of limestone which had fallen upon the floor would 

 have prevented the possibility of discovering whether it had been the habitation of carnivorous quadrupeds. 

 Like most caverns in limestone its sides and rifts are ornamented with stalactites. 



2 The spot here indicated (the property of the Right Honourable Frankland Lewis) is still nearer to the great 

 non- calcareous region than any of the present works. 



