486 T. C. Cantrill — Coal-boring at Presteign, Radnorshire. 



In the hollow left by the removal of the limestone only one small 

 exposure of that rock is now visible. It shows about a foot of 

 light-grey crystalline limestone, somewhat nodular and concretionary, 

 and apparently sheared and disturbed, overlain by 6 feet of olive- 

 green mudstones, containing flattened nodules of blue-hearted tough 

 argillaceous limestone, and dipping northward at 20°. These mud- 

 stones with nodules evidently form the base of the Wenlock Shales. 



These basement-beds are again well-exposed at the western end of 

 the openwork, where they yielded a few fragments of graptolites, 

 identified as of the Monograptus colonns or M. dubius type by Miss G. L. 

 Elles, who suggests that the beds are not Wenlock but Lower Ludlow; 

 though how this can be so is difficult to explain, since the beds are 

 within 10 feet of the top of the Woolhope Limestone. Higher beds 

 are to be seen at the mouth of the drift (Fig. 1), where they dip 

 northward at 70° to 80°, and yielded Phacops caudatus (Briinn.), 

 Plectamlonites transversalis (Wahl.), and crinoid ossicles. 



The materials brought out from the drift show that the beds cut 

 through are the Wenlock Shales, the Woolhope Limestone, and the 

 Upper Llandovery Sandstone, as might have been expected. ~No 

 other rocks were seen on the tips, though it is possible, as will 

 appear later, that Archaean rocks were reached. A specimen of 

 shale collected from this debris by Professor E. J. Garwood shows 

 a graptolite, which has been identified by Miss Elles as Monograptus 

 flemingi (Salt.) ; another graptolite she suggests is M. vulgaris, Wood, 

 or M. dubius (Suess). A piece of calcareous grit yielded Petraia sp. 

 Unfortunately the drift descends at a slight angle from the horizontal, 

 and in September, 1915, was derelict and full of water. It was 

 therefore impossible to make any examination or measurements of 

 the beds cut through, and no particulars appear to have been recorded 

 while the exploration was in progress. 



Erom the details given above the identity of the rocks as Silurian 

 is put beyond doubt. But the structure of the ground is revealed 

 more clearly by the record of the boring than by the surface 

 exposures. There is, however, strong suggestion of faulting in the 

 manner in which the outcrop of the Woolhope Limestone along the 

 northern side of the ridge comes to an end both eastward and west- 

 ward. The outcrop commences abruptly about 120 yards north-west 

 of the old Corton quarry (Fig. 1). It then runs obliquely up the 

 ridge through an old overgrown limestone quarry, crosses the Folly 

 Farm lane, and then traverses the long openwork already described 

 till it reaches the eastern boundary of Nash and Caen Wood, where 

 the quarrying seems to have stopped. But the strike of the beds 

 exposed at the western end of the openwork would carry the lime- 

 stone outcrop down the slope again towards the foot of the ridge, 

 where an attempt appears at some time to have been made to reach 

 it by shafts, one of which can be seen just within the northern edge 

 of the wood some 200 yards to the north-west. It is therefore 

 probable that the disappeai'ance of the limestone in each direction, 

 after a course of only 800 yards, is due, not to thinning out, but to 

 faulting. This supposition is confirmed by the evidence of the 

 borine. 



