File:The Quarterly journal of the Geological Society of London (13889239499).jpg

ROCKS or PEMBROKESHIRE.
537
has caused the errors to be committed here as in the other areas
referred to. Moreover, Dr. Geikie's statements tend to show that
the examination here of the actual facts must have been im-
perfectly carried out ; for the most important point of contact of
the Cambrian with the Dimetian, shown in fig. 10, is not even
referred to.
Fig. 10. — Section slioiving contact of Cambrian with Dimetian in
Cliff at Ogof-Uesugn.
Diabase dyke. F. Cave.
Cambrian.
When the Director-General read his paper, even minor faults were
condemned by him. In a footnote, inserted after the discussion, it
is stated, however (p. 277), that " possibly some slight displacement
may have taken place at Ogof-llesugn ; but the mass of con-
glomerates is imbedded in the granite." This does not very much
improve the statement in the text on the same page that the
" granite which extends continuously eastward from Porth-lisky,
abruptly ends off and is succeeded at once by vertical sandstones and
shales which are truncated by it nearly at a right angle." The
point where the conglomerates and sandstones touch the Dimetian,
and, according to the Director-General, are truncated by it, is shown
in fig. 10, and I believe that those who have examined the spot, and
they are now many, will admit that this sketch gives a fair repre-
sentation of the Qonditions to be seen. It shows the Dimetian to be
sharply defined, with some beds of the Cambrian conglomerate lying
against it. The line of fault is clearly indicated by fault-breccia
above and by a narrow cavern below, into which some of the younger
members of Prof. Hughes's party were able to squeeze themselves
for several yards. As much higher beds of the Cambrian series
than these are found, directly to the north, to strike up against the
Dimetian, it is clear that these beds are bounded at Ogof-llesugn
by two faults, as shown on the map (PI. XXIY.). These probably