part 1] ON THE GEOLOGY OP THE OLD BADNOE DISTHK 1. 9 



-does a tourmaliniferotis granite of great antiquity. This iron- stained pebble 

 when sliced showed interlocking crystals of albite. perthite, quartz, and 

 subordinate museovite, together with big well-developed crystals of greenish- 

 blue tourmaline. 



Pebbles of dstrital rocks other than the characteristic quartzites are not of 

 frequent occurrence ; but well-foliated quartz- schists, fine-grained micaceous 

 sandstones, as well as a garnetiferous arkose, are represented. 



The errey conglomerate is characterized by an abundance of well- 

 rounded grey and white quartz-pebbles, although a few pebbles 

 of pink quartzite also occur : hut the red felsite-pebbles, so con- 

 spicuous in the pink conglomerate, are rare. A few pebbles of 



crystalline schists have also been collected from rocks of this type, 

 in the exposures on Old Radnor Hill ( PI. II ). This grey con- 

 glomerate is well exposed in a small field on the north side of the 

 road running from Old Radnor to Walton, immediately west of 

 Stockwell Farm, where it forms a prominent feature. It can be 

 traced into the road, but appears to be cut off south of it by the 

 dislocation which brings down the limestone immediately to the 

 east. The small outcrops of conglomerate which occur along the 

 edge of the wood, east of the Old Castle mound, may. however, 

 represent fragments of the same bed. North of the road the 

 conglomerate is cut out by another dislocation, and disappears 

 before reaching the old quarry on the south side of Wellin Lane. 

 This fault is evidently a continuation of that which has already 

 been mentioned as running: along the lane to Stones Farm, and 

 the isolated outcrops of grey conglomerate which occur in the 

 field north of Stockwell Farm are therefore, in all probability, the 

 Stockwell- Farm bed shifted eastwards by this fault. A similar 

 grey conglomerate also occurs in several isolated outcrops round 

 the southern margin of Old Radnor Hill, immediately north 

 of Hillhouse Farm; and again in two exposures in the triangular 

 field below the farm, on the east side of the Dolyhir- Radnor road. 

 These outcrops all have a general north-north-westerly strike, and 

 are cut oft" abruptly on the south by an east-and-west fault which 

 briners in the limestone on the southern margin of the hill. 

 Whether these exposures represent faulted outcrops of the same 

 bed. as suggested on the map. is difficult to determine: but their 

 general similarity in composition and the parallelism of their strike 

 renders it probable that this is the case. 

 Dr. Thomas reports as follows: — 



The pebbles of the grey conglomerate are similar to those of the pink 

 conglomerate, but the beds of this horizon differ from the pink conglomerate 

 chiefly in the relative proportions of the rock- types represented. Here again 

 we meet •with the same suite of albitic rocks. The white to grey superficially- 

 stained epiartzite and other fine-grained quartzose sedimentary rocks are 

 relatively abundant, while the pink quartzite so characteristic of the pink 

 conglomerate is less frequently met with. 



A red-stained albitized basalt, with well-shaped microporphyritic pseudo- 

 morphs after olivine, occurs in one of the outcrops of the conglomerate on 

 Old Radnor Common. 



The green felsitic and keratopkyric rocks occur perhaps in slightly greater 

 force than in the pink conglomerate ; but, taken as a whole, there is strong 

 evidence for the view that both the pink and the grey conglomerates have 

 been derived from common sources. 



