56 DR T. J. JEHU ON 
lisky farm. ‘‘ The picrite boulder has been shown by Professor Bonnry to resemble 
masses of that rock exposed in Carnarvonshire and Anglesea, and the granite boulder, 
which before it was broken must have been over 7 feet in length and 3 to 4 feet in 
thickness, is identical with a porphyritic granite exposed in Anglesea, but not found 
anywhere in Pembrokeshire.” He found clear evidences showing that St Bride’s Bay 
was overspread by a great thickness of drift from the hills immediately to the north. 
“The intervening preglacial valleys were also filled by this drift, and the plains and 
rising grounds up to heights of between 300 and 400 feet still retain evidences of its 
former presence, and many perched blocks.” Chalk flints were found at heights of 
over 300 feet, and have probably come from Ireland. He refers also to the crushing 
and bending of the strata at places, and to some well-marked examples of “crag and 
tail,” but he does not locate these phenomena. j 
The late Professor PRestwicuH, in his paper on “The Raised Beaches and ‘ Head’ 
or Rubble-Drift of the South of England” (Quart. Journ. Geol. Soc., vol. xlviii., 1892), 
refers to the possible occurrence of this rubble-drift on the coast of Pembrokeshire. He 
thought that he had detected traces of a raised beach and ‘head’ near Porth Clais, 
and again at Whitesand Bay. 
Professor Bonney, in his [ce- Work (p. 161), states that “In Pembrokeshire and the 
adjoining districts erratics are often abundant, as may be seen near St David’s. At 
present no systematic attempt has been made to trace them up to their sources, but 
they have probably come from the higher ground inland, that is to say, roughly, from 
the north-east.” And again (p. 165) he refers to the possibility that the northern ice 
travelled down the bed of the Irish Sea, and perhaps ultimately overflowed St David’s 
Head. 
Dr Wricut, in his book on Man and the Glacial Period, remarks that “ At St 
David's peninsula, Pembrokeshire, strize occur coming in from the north-west, and, 
taken with the discovery of boulders of northern rocks, may point to a southward 
extension of a great glacier produced by confluent sheets that choked the Irish Sea” 
(p. 148). 
Mr Cowper ReeEp, in the paper already referred to, mentions the fact that “ drift 
or boulder-clay causes a difficulty in tracing the boundaries or determining the 
characters of the underlying beds” in the Fishguard district. 
Ill. Puysicat FEATURES AND GEOLOGY OF THE DisTRICT. 
The county of Pembrokeshire lies in the extreme south-west corner of the 
Principality, and that part of it which is under consideration in this paper extends 
further to the westward than any other part of England and Wales, with the exception 
of the extremity of Cornwall. The promontory of St David’s is washed on three sides 
by the sea which has eaten into the land so as to give rise to a variety of recesses and bays. 
It is the presence of hard igneous rocks that has enabled it to resist the ceaseless action 
