80 DRL. J. SREY, -ON 
what are undoubtedly northern rocks associated with these boulders of diabase at | 
Cardigan. 
Of the erratics the most important discovery in the drift was that of a small boulder 
of the Ailsa Craig riebeckite rock, or paisanite. This was found in the bluish boulder- 
clay, near the surface, at Clun-Bach moor, St Nicholas, near the south-western end of 
Strumble Head. The specimen was sliced, and as seen under the microscope it is 
identical with specimens obtained from Ailsa Craig. 
Boulders of hornblende-porphyrites from the south-west of Scotland occur in the 
Lower Boulder-Clay as far east as Cardigan, and are found even oftener in the Upper 
stony Boulder-Clay. Several varieties are seen, all of which can be matched in Wig- 
townshire and Kirkeudbrightshire. But the erratics which are most commonly met 
with in the drift are reddish granophyres, quartz-porphyries and micro-granites. 
Many of these are dyke-rocks, and it is very difficult to trace them to their source. 
Some have certainly come from Ireland, and some most probably from the south-west 
and west of Scotland. Lake District rocks and North Wales rocks are not so well 
represented, 
In the clay-pits of Rhos Isaf, near Dinas, excavated in the Lower Boulder-Clay, a 
reddish granophyre was found, which, under the microscope, resembles very much some 
of the granophyres of Mull. And in the Pen Creigiau gravel-pit boulders of granophyre 
occur, which have come from the Carlingford district, Ireland. One was sliced, and the 
microscopic characters seen were identical with that of the granophyre of Barnavaine, 
Carlingford. These reddish granophyres are found in the drift throughout the area, 
but seem to be rather scarcer in the extreme west. As the writer had not much 
opportunity of comparing them with Irish rocks, he sent them to Prof. Warts, of 
Birmingham University, who very kindly examined them. Many of the granophyres, 
he thinks, can be matched in the Carlingford mountains ; others bear more resemblance 
to the Tertiary granophyres of the Inner Hebrides. The reddish quartz-porphyries 
appeared to him to be like the varieties of the quartz-porphyry of Cushendale in 
Antrim; and among the boulders of micro-granite he noted two which are likely to 
have come from the mass of micro-granite at Cushendun in Antrim. He is of opinion 
also that the Old Red conglomerate of Cushendun might, when broken up, present 
examples of many of the types of boulders found in the drift of Pembrokeshire. A 
pebble of muscovite-granite, probably the Foxdale granite of the Isle of Man, was 
obtained from the gravel-pit at Pen Creigiau, over 600 feet above sea-level. Examples 
of Millstone Grit were obtained here also, and in the Cardigan clay-pit boulders of 
Carboniferous Limestone are common, often with the fossils well preserved. On 
the beach at Gwhert, not far from Cardigan, boulders and pebbles of Carboniferous 
Limestone are common. ‘These must have come from Ireland or from carboniferous 
rocks which are hidden at the bottom of the Irish Sea. It is hardly likely that they 
have come from the small exposures bordering the Menai Straits in North Wales. 
Chalk-flints occur everywhere—in both boulder-clays, in the sands and gravels, and 
