THE GLACIAL DEPOSITS OF NORTHERN PEMBROKESHIRE. 57 
of the waves, which, owing to the direction of the prevalent winds, often beat upon the 
coast with great fury. The softer Lower Paleeozoic slates and Carboniferous shales to 
the south have succumbed to the encroaching sea, and there given rise to the broad and 
wide bay of St Bride's. The islands lying to the west consist partly of hard igneous 
rocks, and no doubt were once joined to the mainland. The coast scenery is magnificent, 
and throughout this region the rocky cliffs rise steeply out of the sea, and sandy beaches 
are only found here and there, such as at Whitesand Bay, Abereiddy Bay, Abermawr, 
Goodwick Bay, and Newport Bay. The cliffs in places are nearly perpendicular, and 
everywhere exhibit excellent sections of the rocks. The outline of the coast is very 
jagged, reefs and stacks of rock sticking out here and there, whilst, on the other hand, 
the sea has penetrated in so as to form caves and coves, and small narrow 7ia-like 
channels, such as that seen at Porth Clais at the mouth of the Alan river, and that at 
the mouth of the Solva river. A silted-up estuary occurs at Abermawr to the west 
of Strumble Head, and a larger one on the east side at Goodwick Bay ; they now form 
swampy ground. The only other estuaries of importance lie on the north-east side of 
Strumble Head, at the mouths of the rivers Gwaen, Nevern, and Teifi. That of Gwaen 
is also somewhat ra-like in character. 
On the north coast Strumble Head is a prominent feature and stands out boldly 
to sea, and a little further to the north-east a small but well-marked headland occurs at 
Dinas. 
The one-inch Geological Survey maps of this part of Wales were prepared before the 
end of the first half of last century, and no revision has yet been made. Since that 
time a more complete knowledge of the fossil contents of the sedimentary series has 
been obtained, and improved methods for the study of igneous rocks, especially with 
regard to their microscopic structure, have been introduced. The need for a fresh 
survey is generally recognised, but much new light has been thrown on the geology of 
St David's promontory during the last thirty years through the researches carried on 
by Dr Hicks, Sir A. Grrkiz, and others. And Mr Cowper Reep has examined and 
described within recent years the geology of the area around Fishguard. But the 
region is a very complicated one, and much of the geology still remains obscure. The 
rocks of this part of Pembrokeshire are almost entirely of Lower Paleozoic age, and a 
remarkable variety of both the igneous and sedimentary kinds is there displayed. In 
the St David’s region a very full development of Cambrian rocks is exhibited, and these 
are underlain by a series of volcanic rocks—both series often showing signs of meta- 
morphic changes. The base of the Cambrian was taken by Dr Hicks to be marked by 
a conglomerate in which are enclosed pebbles of the underlying rocks. The volcanic 
tuffs and breccias which underlie the conglomerate were taken to be pre-Cambrian. 
Underneath these again comes a granitoid mass, which he regarded as still older. 
Later, the district was visited by Sir A. Grrxte, who, after an examination of the ground, 
arrived at the conclusion that the granite is an intrusive mass, and that there is no 
break between the Lower Cambrian rocks and the volcanic series underlying them. 
