Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/530

 W. of Porth Clais, purple sandstones, which will be shown to be higher in the series than the greenish flaggy rocks, strike against the quartziferous breccias, affording further evidence of the occurrence of a fault in this neighbourhood.

It has been stated that at the ruins of Nun's Chapel the compact quartz rocks are in connexion with the quartziferous breccias.

At this locality there are seen resting, apparently conformably, on the compact quartz rocks, conglomerates already referred to as being composed of large and well- rounded masses of quartz imbedded in a purple matrix. These conglomerates, as here seen, are about 30 feet in thickness.

The same conglomerates are well shown near Clegyr Bridge, where they appear to be conformable to the underlying compact quartz rocks, their dip being towards the S.S.E., at about 80°. In this locality the thickness of the conglomerates amounts to about 60 feet.

On the N.N.W. side of the axis of the quartziferous breccias no compact quartz rocks are recognizable ; but some fine-grained yellowish beds of a soft and decomposing nature are seen in contact with the quartziferous breccias, and are succeeded by purple conglomerates.

The section on the S.S.E. side of the axis exhibits a good development of greenish flaggy sandstones identical with those alluded to as occurring at Porth Clais Harbour ; and these sandstones are conformable to the conglomerates on which they rest. The greenish flaggy sandstones have been worked, especially at Caerfai; and a small quarry of them is also

Fig. 1.-Section across the St. David's Promontory. (Corrected by Mr. Hicks, September 1871.)