262 A. B. Badger — Exposures of Quartz- Felsite 



it is covered by conglomerates and grits, while to the south-east there 

 is low-lying swampy ground, the boundary on this side probably being 

 a fault. The rock is grey in colour, and at the south-western end of 

 the exposure near the farm buildings flow-structure is well displayed 

 on the weathered surfaces ; elsewhere, however, this is not so apparent. 

 The microscopical characters are generally those of the Cwmyglo rock, 

 but specimens from the eastern side do not show flow-structure, and 

 are much decomposed and brecciated. 



There do not appear to be any other exposures of the quartz-felsite 

 between this point and those so well known near the north-west end 

 of Llyn Padarn, some five miles away. 



(2) Gwirfai River, near BontnewyM. — The small village of Bont- 

 newydd is about two miles south of Carnarvon. A quarter of a mile 

 to the east the ground rises into the hilly slopes which lie in front of 

 Mynydd Mawr and Moel Eilio. Debouching from a somewhat narrow 

 channel, cut through this higher ground, the Gwirfai River flows 

 eastward from Lake Cwellyn through Bontnewydd to Carnarvon Bay. 

 The Geological Survey Map shows the river as traversing the quartz- 

 felsite from Bettws Garmon to within a mile and a half of Bontnewydd, 

 and for the next mile and a quarter as traversing Cambrian grits and 

 conglomerates. Stratified rocks, however, do not occur for all this 

 distance ; they crop out about two-thirds of a mile west of the quartz- 

 felsite, and from this point extend for 300 yards to the west. Again, 

 just at the opening of the gorge grits and conglomerates are found, but 

 for some 600 yards east of that opening the sides of the gorge are 

 formed of quartz-felsite. The latter rock shows numerous phenocrysts 

 of quartz and felspar, the first-named mineral being much cracked. 



It may be remarked in passing that the stratified rocks which are 

 found at the mouth of the gorge lie directly on the felsite and 

 comprise grits of quartz and pink felspar, and ver}- coarse con- 

 glomerates which have a remarkable resemblance to those so well 

 known at Llanddeiniolen. 



(3) Gadlys Farm. — In a lane leading from the main road a little 

 north of Llanwnda Railway Station there is a small opening in which 

 pink quartz-felsite is exposed. 



(4) Llanwnda Station. — Half a mile to the south-west of the last 

 exposure, quartz-felsite is again exposed in a few patches on the 

 eastern bank of the railway cutting some 100 yards south of the 

 station. 



(5) Glynllifon. — The next series of exposures occurs in Glynllifon 

 Park, the residence of the Hon. Frederick Wynn, owing to whose 

 kindness it is that I have been able to examine this locality. The 

 Geological Ordnance Map marks the eastern half of Glynllifon as 

 '■'altered Cambrian Sandstone," probably because the surveyors mistook 

 the quartz-felsite noted below as exposed in Coed Penbrynmawr for 

 a metamorphic rock. The other exposures, however, to which I refer, 

 occur in parts of Glynllifon marked on the map as unaltered Cambrian 

 Grits and Conglomerates. 



Most of the exposures of the igneous rock are found in or near the 

 narrow valley of the little stream called the Afon Llifon, which here 

 extends from the so-called ' East ' Lodge on the north for a distance 



