VOLCANIC GROUP OF ST. DAVID’S. 299 
Fig. 4.— View of Carn-ar-wig from the north. 
Ww 
Schistose Stratified ’ Conglome- 
ash. ash. rate. 
\ 
A 
4 
NS 
Intermediate Agglomerate. Green ash. 
Felsite. 
Of these the rocky inlet of Ogof-Llesugn is doubtless the key; it 
has been brought forward as a crucial test of the true relations of 
the two series of rocks, and held to prove the idea of a Pre-Cambrian 
granite to be a delusion. This being the case, it ought to be 
described with care. J am at a loss how to characterize the de- 
scription that has actually been given of it without offence; but I 
must at least say that the essential feature has been missed. A plan 
of the spot is presented below (fig. 5) :—On the west side of the inlet 
we have the granite mass, on the east side the nearly vertical beds 
of the Cambrian some way above the base, striking straight at the 
granite. In the angle between these is a projecting mass of con- 
glomerate, also apparently vertical and striking nearly at right 
angles to the other Cambrian beds, so far as can be ascertained, the 
stratification being obscure. ‘This projecting mass is bounded on 
either side by a fault which has given rise to a cavern; that on the 
east side, between the conglomerates and the slates, extends ? mile 
inland, or to about the position of the Porthclais mill; both are 
characterized by their fissure-like straight aspect, their slickensides, 
and the discordance of the adjacent beds. ‘There is some bending 
round of the slates near the fault, as if to get into the same strike 
as the conglomerate, which contains some tuff-like masses, but is 
unaltered from its usual appearance on this side. On the western 
side, where the granite is, the line of fault has been invaded by a 
. 
