5A DR T. J. JEHU ON 
the facts that geographically the region lies further south, and that it does not present 
such a great elevation of the land above sea-level, it is not to be expected that 
Pembrokeshire will show such marked traces of the former presence of glacial conditions 
as are to be met with in North Wales. Nevertheless, it has been known for a long 
time that this region is to a large extent covered by more or less loose and uncon- 
solidated material, which is usually spoken of as Drift. And references are found 
scattered in the geological literature of the district relating to travelled boulders and 
other possible glacial phenomena there seen. But hitherto no attempt has been made 
to give a connected description of the glacial deposits with a view to the unfolding 
of the sequence of events which occurred during and after the Glacial epoch, and of 
correlating the results obtained by an examination of this area with those derived from 
a study of glacial deposits in North Wales and other regions. The need for further 
investigation will be evident to anyone who compares the map (plate i.) in Professor 
JaMES GEIKIE’s work on The Great Ice-Age, illustrating the British Isles during the 
Epoch of Maximum Glaciation, with the late Mr Carvitt Lewis’ “Sketch Map of 
England and Wales showing the Edge of Land Ice,” which is reproduced in Professor 
Bonngy’s Ice-Work. In the former the southern boundary of the great ice-sheet 
is made to pass beyond Wales and run along the Bristol Channel; and the northern 
ice which overwhelmed Anglesea is marked as crossing the western end of the Lleyn 
promontory of Carnarvonshire, and, joining the Irish Sea, it fills up St George’s 
Channel and crosses the extreme tip of Pembrokeshire at St David’s Head. In the 
latter the land-ice is shown as not extending over the whole of South Wales to the 
Bristol Channel, but with its southern edge extending no further south than is indicated 
by a line drawn eastwards from the St David’s promontory, and the glaciation of 
Northern Pembrokeshire is attributed solely to local ice—the northern ice apparently 
extending no further south off the Welsh coast than the Lleyn promontory. 
The results obtained during the investigations carried on by the present writer will 
at any rate serve to settle the dispute with regard to the southward extension of the 
Northern or Irish Sea Glacier. 
Il. Previous LirERATURE. 
References to the surface deposits and surface features of Pembrokeshire are meagre 
and scanty in the extreme. 
Sir Rk. Murcuison, in The Silurian System (p. 520), makes the following remarks : 
“The detritus which appears on the surface of most parts of Pembrokeshire is of a 
simple character and, as in other parts of South Wales, is of local origin. It consists 
of fragments of greenstone, porphyry, carboniferous grits, etc., all of which can be 
traced to the various mountains forming the crest of the country. In some parts this 
detritus is exceedingly coarse... . In other tracts, as north of Haverfordwest, we meet 
with finely comminuted gravel ; but this is rare.” 
