The limestones of North Wales form two roughly parallel exposures. On the west side of the Vale of Clwyd one runs SE from the Great Orme. The other, on the east side of the Vale, run SE from Prestatyn via Rhydymwyn, Cilcain, Loggerheads and Llanarmon-yn-Ial to Llandegla. Here it is stepped eastwards to Minera by a fault. South of Minera the exposure runs south and its western edge displays the impressive escarpment of Eglwseg, near Llangollen. It is the area between Rhydymwyn and Loggerheads in which we are most interested. The general North Wales limestone areas have been reviewed by Meeson (1).
The area between Loggerheads and Rhydymwyn has been discussed in detail by Appleton (2). This area is of particular interest because the River Alyn, which flows in wet weather beyond Rhydymwyn (SJ 204668) normally sinks entirely in swallow holes in the region just north (downstream) of Loggerheads (SJ 197628).
Mine drainage levels were driven in 1901 from sea level to about 225 feet above O.D. in the region of interest. The water which sinks at Loggerheads used to reappear in springs further down the valley, flowing via a phreatic system, but as a consequence of the Sea Level Tunnel, the strata were drained. The amount of water sinking at Loggerheads increased dramatically.
The drainage of the strata has made accessible the various phreatic systems which were previously flooded. The first of these to be discovered and explored was Ogof Hesp Alyn (Dry Alyn Cave) (2). A full exploraton of O.H.A. is a fair trip; in addition the cave fills completely with water in very wet weather.
The area betwenn Rhydymwyn and Loggerheads is criss-crossed by shattered compressional N-S faults (crosscourses) of an open nature, and mineralised E-W faults (veins and lodes). A correlation survey of O.H.A. and the fault system found that the former is strongly controlled by the latter. About a hundred metres upstream of O.H.A., the river intersects an unnamed mineralised crosscourse, which is the site of the old Dyer's Adit, and further upstream still the Caleb Bell crosscourse is intersected. An inspection of the latter point showed nothing, but at the former point, above where the North Wales Caving Club had at one time tried to dig into the adit, more encouraging signs were found. Above the footpath (which crosses the adit) the fault is exposed; a short dig here among some collapsed debris soon revealed a draughting hole (which Gordon said would 'go').
The dig was started in earnest on June 18th, 1978, with several members joining in from far afield. Progress was not difficult, involving the removal of mainly sand, clay and boulders of various sizes, but also, at the far end, a 10-cm thick compacted layer of evil-smelling animal excrement was encountered. The cave revealed was a natural, horizontal tunnel, well scalloped, 0.9 by 0.9 metres on average and 7 metres long.
At the far end we had a choice of directions in which to proceed. The scalloped solid passage (which we did not pursue) continued ahead, while on the left we had entered a small alcove full of fractured blocks and pieces of stalagmitic deposit. Much of this was removed, allowing a draught to be detected through the choke. It was in this highly promising situation that the dig had to be put reluctantly in abeyance in favour of holidays.
On returning from our months here and there, we were delayed in recommencing excavation by various illnesses and the like, but eventually returned to work on the 14th September. We were not too pleased to find that we had been given some unsolicited help with the project by a couple or so volunteers, who had dug down our choke, entered the adit and from there the new phreatic series. Little detective work was necessary to discover the names of the poachers who claimed, of course, that our dig had been abandoned. They seem to have ignored the following announcement from their own reporter in their newsletter No. 67 (3) which appeared in late July - 'They (the N.P.C.) are now digging above what is thought to be the old Dyer's Adit.... attempting to open a silted natural passage at which it is believed there is a draught'. In their September Newsletter (4) they admit having taken over the dig on August 16th. They have since been censured by the Cambrian Caving Council (5,6). The present author published a brief account in 'The British Caver' (7). As a result of this, both he and Tony Oldham have been threatened with libel actions by a Mr. A. Hawkins. This letter has been published (8).
Our first encounter with the poachers was potentially an extremely explosive one. To his great credit, Dave Raine (totally out of character?) made an uneasy peace. It was agreed that we should gate the cave (it IS Wales); N.W.C.C. provided the lock (key no. P.E.S.6).
An entrance crawl of 7 metres leads to a pitch of 5 metres (ladder required) which is narrow at the top. Right (facing the ladder) leads to a boulder choke at the original exit end of the adit; at the foot of this on the left is a small hole leading to the Old Springs Passage. This starts as a crawl on a solid rock floor bearing large scallop markings, which indicate an outward flow of water (as do the markings everywhere in the cave). The flat roof is dissected assymptotically, there being little of the thin limestone bed remaining to support it. Further along, the solid floor gives way to silt and at te sides of the passage are mudbanks, the remains of a previous infill. These banks are present everywhere in the cave with the exception of the lower streamway. From the roof hangs a profusion of long, very thin tree roots, mud encrusted, eerie in the silence and swinging gently in the breeze. This first section of the cave appears very oppressive to some.
Soon the passage begins to gain height, becoming alternately of walking and stooping dimensions with the higher parts above the mudbanks and bearing some 'moonmilk'. The passage varies in cross-section from the traditional oval phreatic tube to triangular as at Isoceles Passage.
Before long, the passage intersects the Caleb Bell crosscourse. Here, the nature of the cave changes dramatically, the fault having been dissolved out into a high rift. There are chambers with excellent examples of cracked mud floors. One exit from the rift chamber is a climb up to the right which termionates in a circular shaft. The alternative exit, down to the left, leads to a chamber with a mud slope floor below an unhappy-looking rock bridge. At the bottom of the slope are two holes. On the right is a steeply sloping, extremely muddy tube ending in a vertical drop; the other, on the left, is a clean, circular shaft (the downwards cintinuation of the shaft in the rift chamber). It is pointless descending either of these since their lower reaches can be gained with ease from the lower stream passage.
The way on from the holes in the floor is up a muddy slope into a mud floored phreatic tube leading, via a small chamber, to the top of a steep mud bank. At the bottom of the slope is a large cavern sporting an active streamway, the only one of any significance so far discovered in North Wales. To the right the upstream passage is large, being 6m wide by 5m high in places, but to the left the water disappears amongst the boulders to enter a more restricted, highly shattered region as it follows the fault down towards O.H.A. It is possible to explore, via unsafe chambers, to a point at the bottom of the holes encountered earlier, and beyond, through muddy tubes, to a rift. Ahead, across a static pool containing shrimps, a second, small stream enters from a boulder choke, while down to the right is a slot 1.5m deep. At the bottom the slot continues as a tight, low crawl from which issues the roar of the main water.
The upstream section from where the river is met continues in grand proportions for a while, but eventually the mud banks close in, the roof lowers and one is forced to crawl in water for a few metres in two places. (These have been observed personally with only 12 cm of airspace and there is no doubt that in wet weather they would readily sump off). Beyond the low sections the roof rises quickly to around 5m and a few stalactites are seen. Before ong a circular chamber, 16m in diameter by about 12m high, is entered, containing, on the right, a huge stalagmite boss with accompanying flowstone cascade above. A flat section of roof on the left displays a profusion of fossil brachiopods (Schellwienella crenistra).
There are two exits from the main chamber. To the left is a descending shattered rift which, in wet times, fills completely and from which a large amount of water flows to swell what is normally the main stream.
Across the chamber the main stream continues along a passage 3m by 3m, which contains some passable formations. The roof lowers to 0.5m at a joint where the stream enters on the right. Here a slide up a muddy hole leads to a final, enormously shattered chamber, whose roof is suspended by as yet undiscovered forces.
Tree roots are again seen, this time thick ones in the mud, and traffic can be heard at Cilcain bridge (which is shown by the surey to be very close).
The prospects for further extension appear good. The boulder-choked rising at the large chamber would require a large scale dig, but the lowest pint reached (the tight crawl) could soon be passed and possibly lead to the discovery of passages to O.H.A., Loggerheads or both.
The length of the main passage from the entrance to the final shattered chamber is 650m; the total surveyed passages total almost 0.8km.
It should be noted that the cave is dangerously flood prone. In wet weather the old springs at Dyer's Adit still flow. Personal observation when the River Alyn was in spate confirmed the circular shaft in the fault section of the cave to be full to the top with water and all traces of bootmarks to have been recently eradicated from the entrance series. The Old Springs Passage has been observed to be sumped at a point only 100m from Dyer's Adit. The level of water in the river is probably not indicative of the local subterranean water table. O.H.A., which is situated about 100m downstream at Poacher's Cave, fills completely with water at times, and the floods can take up to a fortnight to subside.
The diggers: E. Hoole, N. Beatty, R. Beatty, B. Hryndyj, M. Jenkins, D. Brandon.
Footnote: The North Wales Caing Club have negotiated an agreement with the Water Authority, giving them sole right to control access to the cave. They have changed the lock.