ROCKS OF PEMBROKESHIRE. 511 
rocks in the district, and that the Cambrian rocks were largely built 
up of materials derived from them by denudation. They maintain 
that the felstones areintrusive rocks of later date than the sedimentary 
rocks. I hold that they also, for the most part, are of Pre-Cambrian 
age, but newer than the granitoid rocks, that the majority are old 
rhyolites or breccias, and that Dr. Geikie’s so-called apophyses actu- 
ally in places cut through the Dimetian rocks. Fragments of some 
of these are found abundantly in the Cambrian conglomerates. 
The next point of importance is that relating to the connexion 
of the volcanic series with the Cambrian. The Director-General 
maintains that they are merely the lowest beds of the Cambrian. 
I hold that there is an abundance of evidence to show that they 
are truly of Pre-Cambrian age, that the Cambrian rocks are very 
largely indeed made up of fragments and finer materials derived 
from them by denudation, and, moreover, that the basal Cambrian 
conglomerates constantly overlap different members of the volcanic 
series. 
The differences between the views of the Survey and my own remain 
therefore almost equally great after the resurvey by the present 
Director-General as they were before. As some points of importance 
in regard to the nature and distribution of many of the rocks have 
been made out since my paper in 1879 was published, 1t will be 
necessary for me to add some special remarks on each of the three 
groups into which they have been divided by me at St. David’s, 
before referring in detail to the various points at issue between the 
Director-General and myself. 
V. Tue Diwertian Rocks. 
a. Huidence of Age.—That the Dimetian rocks are older than the 
Cambrian rocks has been proved, as I shall show, beyond the possi- 
bility of dispute, by the finding of an abundance of well-rolled frag- 
ments of typical Dimetian in the Cambrian conglomerates, and by the 
fact, proved by examination with the microscope, that the matrix 
of the conglomerate and also some of the grits and sandstones flanking 
the Dimetian at various points, are almost entirely made up either of 
minute fragments, or of the characteristic felspar and quartz, of the 
Dimetian. 
The importance of these finds will be readily recognized by those 
who have taken part in or watched the discussions on these ques- 
tions; for it has been constantly assumed by those opposed to my 
views, that these fragments could not be found. Moreover, the 
Director-General in his paper (at p. 288) makes the following state- 
ment :—‘‘ As the result of a most careful examination of the con- 
glomerate belt along both sides of the fold I feel myself warranted 
in stating confidently that it contains not a single pebble of the 
characteristic granite of the St. David’s ridge.” The making of 
such a definite assertion, founded on negative evidence alone, seemed 
to me at the time rash in the extreme, especially as I had on several 
occasions, even without looking with any particular minuteness, found 
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