Environmental Engineering Reference
In-Depth Information
one of the most photographed landmarks in Wales. The Worm is cut off from the rest of the peninsula at
high tide and the natural tidal causeway, between the Inner Head and the mainland, is exposed by the ebb
tide about two-and-a-half to three hours after high water. It takes at least 15 minutes of rough scrambling
to cross the causeway, but as it is only clear for a short time it is always necessary to check the tide times
beforeattempting toreachtheisland.EvenDylanThomas,whowasafrequentvisitortotheWorm,made
the mistake of falling asleep on the Inner Head and had to wait for low tide:
I stayed on that Worm from dusk to midnight, sitting on that top grass, frightened to go further in
because of the rats and because of things I am ashamed to be frightened of. Then the tips of the
reef began to poke out of the water and, perilously, I climbed along them to the shore.
On the south side of the Outer Head is the Blow Hole, an inconspicuous opening surrounded by an
area of bare rock (Fig. 91). The hole marks the end of a long fissure that passes right through the island
to a submarine cave on the north side. Some of the earlier accounts state that the entrance to the cave is
uncovered at very low tides, but this has not been confirmed recently.As the water in the fissure rises and
falls with the swell the air is drawn in, or forced out, through the opening. When the wind is in the west
the Blow Hole was said to produce a strange hollow booming sound and a spray of water that could been
seen from some distance. The conspicuous but intermittent spout-like spray of sea water that can be seen
rising impressively up the north side of the Worm today, when the tide is right and there is a reasonable
swell, is produced by a different rock formation at the outer end of the Middle Head, rather than by the
hole itself. It occasionally rises higher than the Outer Head and can be seen from Cwm Ivy Tor, sever-
al kilometres away. The phenomenon of the Blow Hole was known to William Camden, who visited the
Worm twice in the sixteenth century, noting that:
Toward the head itself, or that part which is farthest out in the sea, there is a small cleft or crevice
in the ground, into which if you throw a handful of dust or sand, it will be blown back again into
the air. But if you kneel or lie down, and lay your ears to it, you will then hear distinctly the deep
noise of a prodigious large bellows. The reason is obvious; for the reciprocal motion of the sea,
under the arch'd and rocky hollow of this headland, or promontory, makes an inspiration and ex-
piration of the air, through the cleft, and that alternately; and consequently the noise, as of a pair
of bellows in motion. I have been twice there to observe it, and both times in the Summer season,
and in very calm weather. But I do believe a stormy sea would give not only the forementioned
sound, but all the variety of other noises.
