THE GLACIAL DEPOSITS OF NORTHERN PEMBROKESHIRE. 63. 
the neighbourhood of Caerfai Bay and Caer Bwdy Bay. In the country between St 
David’s and Strumble Head boulders are also common. Blocks of “ ereenstone ” are 
found around Mathry : the rock is a diabase, probably occurring at no great distance away. 
On Strumble Head the boulders are very plentiful, and the writer found a boulder of 
picrite not far from the extreme head, near the coastguard station, and another further 
south, near Tre-Seissyllt, together with a remarkably fresh olivine-gabbro, of a kind 
which is not found in the district. These will be referred to more fully in another 
section of the paper. Hast and south of Fishguard, boulders of a dark “ greenstone” 
and of a volcanic rock which weathers white are abundant. They are found on the hill- 
slopes, on roadsides, and in the fields, but many have been cleared away as before. 
The Precelly hills are free of boulders as compared with the hills lying further north. 
It may be mentioned that vestiges of antiquity abound in this part of Pembroke- 
shire. Hut circles, ancient entrenchments, cromlechs, British camps, etc. occur at 
places all the way from St David’s Head to Cardigan, being particularly evident at St 
David’s Head and Strumble Head. Some of the ancient British towns or settlements, 
traditions of which are to be found in the old Welsh romances, called The Mabinogion, 
are situated within this area, and one has been identified as occurring on the Garn 
Fawr, Strumble Head. 
IV. Descriprion oF THE Deposits. 
The glacial deposits of the district vary a great deal as traced laterally from 
place to place. Owing to the want of good exposures inland, it is generally impossible 
to mark out the limits of the different kinds of superficial detritus. One has to. 
depend for most part on a study of the sand-pits and clay- or marl-pits which are 
dug in places all over the district. But it is not often that these go down to any great 
depth ; and when occasionally a deep pit has been dug out for the purpose of obtaining 
clay or sand for the land or for building, it is invariably filled up again with surface- 
rubbish, so as not to be a danger to animals. Where a pit appeared to be of peculiar 
interest, the writer employed a man for digging, and in this way obtained some 
valuable sections. At the eastern limit near Cardigan there are brickworks, and here 
it is that the best sections are to be seen. The writer hopes in the near future to con- 
tinue his investigations eastwards in the neighbourhood of Cardigan. The deposits: 
which occur in the district are the following :— 
3. Upper Boulder-Clay and Rubbly-Drift. 
2. Sands and Gravels. 
1, Lower Boulder-Clay. 
1. The Lower Boulder-Clay.— This is a typical boulder-clay which is met with 
in patches throughout the district, but is best and most fully developed towards the 
east. It has received no attention within recent times, but a very quaint and, on the 
whole, a very accurate description of it is found in the works of a writer who lived in 
