6 Mr. De la Beche on the Geology of Southern Pembrokeshire. 



sions are found to consist of trap^ and principally of greenstone. These blocks 

 become less abundant as you approach the cliff. 



Range from Roche to Trafgarn. 



A chain of hills^ considerably elevated above the surrounding country, 

 extends from Cuffern Mountain to Trafg-arn Rocks, most of the highest points 

 in the chain being crow^ned with rocky tors. The most conspicuous of these 

 tors are those of Trafgarn. The less elevated and apparently insulated tor, 

 upon which Roche Castle stands, is connected towards the east with Cuffern 

 Mountain : towards the west, the same mass of rock extends to the distance 

 of about half a mile on the road to Bathesland. Nearly all these tors are of 

 the same kind of quartzose cornean ; in which, however, the proportion of 

 quartz varies, the rock of Roche containing the most. This cornean has no 

 appearance of stratification. Other varieties of trap, however, are associated 

 with the cornean in this range. Blocks of porphyritic greenstone occur at 

 Trafgarn ; and blocks of greenstone and of black porphyritic cornean are 

 found between Roche and Cuffern Mountain. 



This chain is bounded to the north and south by greywacke, through which 

 it appears to be protruded. At its western extremity, near Bathesland, it is 

 covered by coal-measures, over which, at many places in that neighbourhood, 

 are strown blocks of quartzose cornean and greenstone. 



Trap between Druson Haven and Broad Haven. 



A tract between these two havens, consisting of coal-measures and grey- 

 wacke, and extending about two miles from north to south and about half a 

 mile from east to west, is bestrown with blocks of trap, of which many must 

 weigh from five to six tons. They consist principally of greenstone and green- 

 stone-porphyry. The only spot in the neighbourhood where trap appears in 

 situ, is at the hill behind Druson Haven, where the two branches of a rivulet 

 (the one descending from Nolton, the other from Druson) unite. The pre- 

 vailing rock at this hill is greenstone, and it seems to project through the other 

 rocks. Near the trap the greywacke is contorted. (See PI. II. fig. 1.) 



Trap of Gouldtrop Road in St. Bride's Bay. 



From Gouldtrop Road to Millhaven there is a fine and interesting section 

 of the trap and of the other rocks here connected with it. (See PL II. fig. 2.) 

 The rock at Gouldtrop Road is either a syenite or a large-grained greenstone, 

 according as quartz is present or wanting in the mass. Gouldtrop Head is 

 formed of a smaller-grained greenstone. The same rock appears also well 



