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The Exploration of Pant Mawr Pot

The Exploration of Pant Mawr Pot

by Peter I. W. Harvey                                                                                                                                            contents

Aubrey Glennie mentions a trip to Pant Mawr in his obituary to Platten, but does not give a date:Pant Mawr Entrance Shaft

Gerard Platten is perhaps best known to post war cavers as the author and compiler of the British Caver, but he was also an  active and proficient caver, until ill health made caving impossible.  A  notable example was the early descent of Pant Mawr Pothole.  The party was a large one; Gerard was the leader and he kept the whole operation of laddering, lifelining and exploration closely under his control.  At all times in his caving days he did much to help beginners without making things too easy. . . .

Neither Gerard nor Aubrey kept diaries but Platten mentions in a note in the British caver (vol 25 p 29) that he, in company with E. E. Roberts, Gowring and Bill Doyle, descended during Easter 1937.  It is probable that there were several more on this trip, including Aubrey Glennie.  It appears that Jim Braithwaite, Austin Wadsworth and Hywel Murrell were the first to descend; they visited the pot on 18th October 1936, taking up so much gear that they had to hire a horse from a local farmer.  Both Jim and Hywel wrote up their experiences of the exploration.  Murrell wrote, I believe to Gordon Warwick, as follows:

What was, I believe, the first organised examination of the caves in the valleys of the tributaries of the Neath River had been started in Sept. 1936 by members of the Wessex Cave Club.  During the first visit a useful local contact had been made with Jenkin Lloyd, an ex miner, with authiscosis (?) and then a handyman and part time poacher, who made extensive enquiries about possible caves.  Thus we heard about Pant Mawr from a shepherd, and a party consisting of Jim Braithwaite, Austin Wadsworth and H. Murrell visited it on Sunday October 18th. 1936.  Since no cavers had been active locally and the shepherd, an elderly man, had never heard of anyone having gone down, it was I believe the first exploration.  There was no evidence of anyone having been there before.

We hired a pony to carry the ladders (of course we took far too much) and on that occasion explored as far as we could get above the waterfall and found that the “duck” in the first boulder choke was passable.

Our second visit was made on Sunday Nov 15th 1936.  It was a day of driving misty rain and not only did we lose part of the party (Braithwaite, Wadsworth, Murrell, Puch? and some helpers) but we could not for some time find the hole.  Braithwaite and Murrell went through the “duck”, passed another roof fall but were unable to find a way through a third.  We had to return to Somerset that night and gave up when no obvious way on could be found.  We never visited the cave again. . . . .

They probably did not know the depth of the pitch so carried up more ladder than they needed.  There was nowhere round the hole to belay the ladder to so they had to include some form of earth anchor to be driven into the moor.  At that time they were able to pass through the boulder choke and after a few feet were stopped by a further choke.  Jim writes in ‘Caves and Caving’ Vol 1, No 3, page 97, entitled ‘Porth yr Ogof and its neighbours’:                                                        back to the top

Pant Mawr is the high ground to the west of the Little Neath Valley, and it is here that we have made one of our most important finds.  A sink was dicovered on the edge of a boggy saucer-shaped area of moorland, and the hole itself is situated in the centre of this conical depression.  It has been given the name Pwll Pant Mawr.  Being two miles from the nearest track we hired a horse to take the tackle up to it.

On descending, it was found that a 60ft ladder climb brought us to a scree of boulders sloping down to the streamway some 30ft below. The hole opens out into the eastern side of a large chamber.  The stream runs in a N-S direction on the western side.  Going northwards, a passage on the right leads up to a small chamber with a sandy floor, the walls of which are beautifully decorated with stalactite and from here another rift, with shelves of harder rock left projecting along the sides; this leads to the foot of a magnificent 25ft waterfall coming in on the left, a rift leads straight on, and this, after a climb of 40ft, gives access to a low bedding chamber.  A way on was found from here back to the top of the waterfall, and from here there was one of the most inspiring sights I have ever seen.  It is imposible to get upstream any further, as it splits into several small feeders, all too small to permit progress.

Downstream from the main chamber is very easy going.  The chamber opens into a spacious passage.  The stream was followed for some distance before a blockage was reached in the form of a fall from the roof.  There was no way over the fall, but we found a way through the boulders following the course of the stream, although this necessitated total immersion.  The passage resumed its original dimensions again only to continue for a short distance to another fall from the roof - which has not yet been passed.

Lionel Dingle and Greenwood visited the cave later on and were unable to go any further.  It was in 1939 that Dingle, during the B.S.A. Conference in Swansea, led a party down the known part of the cave.

At the Easter meet in the Swansea Valley, beginning Friday 15th April 1949, the SWCC made its first visit to the moors east of the valley, when a large party went up to explore Pwll Pant Mawr.  This was a pothole about a mile to the east of Pwll Byfre, with a 60 ft pitch at the bottom of a 20ft roughly conical depression.  A large party had to be assembled in those days in order to carry all the equipment needed for the descent of the entrance pitch.  We needed about 200ft of rope to tether the ladder, crowbars to provide an anchor, a sledge hammer to drive the crowbars in, 150ft lifeline and 75ft of rope ladder.  All this to descend a 60ft pitch.  The cave at the bottom of the pitch consisted of a main passage, of quite large dimensions, going in a south-easterly direction, approximately 30ft wide and 20ft high.  After about 1000ft, progress was stopped by an impressive boulder collapse.  To the north of the entrance pitch some narrow passages could be followed in the direction of the swallet, which was not far away.                                                         back to the top

I drilled two rawlbolt holes at the head of the pitch.  This allowed  for a 50ft ladder and a lifeline, considerably reducing the weight of tackle required for the climb.  Later on, the Severn Valley Caving Club drove a 10ft railway line into the moor on the level at the top of the depression.  As the passage of cavers increased, the path down the side of the depression to the top of the pitch suffered considerable erosion, which began to indicate that the solid rock I had drilled the bolt holes in seemed to be two boulders resting on others at the top of the cliff.

During these visits  I introduced some fluorescein into the swallet which was about 100 yds from the pothole.  It was assumed that the dye would resurface somewhere in the Neath Valley to the east, but although we kept watch at the likely spots for several days we were unlucky.  I tried again the following Easter with the same result.  It was not until the following year, 1951, when we spent a fortnight in Wales, that we had success and saw the dye coming out at all the risings in the Neath Valley just above Pwll Ddu.  It took five days to traverse the cave.  I had been using ever increasing quantities of the dye and, for the final test, 5lb was used.  I heard later that there was nearly a religious revival at Pont Nedd Fechan on account of the river Neath turning green every Easter.

David Hunt in Pant MawrIn the summer of 1953 John Alexander, with the help of David Hunt and Clive Jones, surveyed the known parts of the cave.  I was in the cave on the 12th September with Bill Clark and Edward Aslett and we had a good look at the boulder choke without finding a reasonable way through.  The whole place consisted of large slabs of fallen limestone interspersed with shale, which did not look at all encouraging.  Bill Little  writes in the SWCC Newsletter  (No. 7,  Jan.’54), summarised here:

The following day Clarke went through, this time with Edward Aslett.  Beyond the wet crawl they crossed a fair sized chamber decorated with straws and some strange stalagmites, and climbed upwards through the second choke.  An Oxbow passage on the left bypassed the next constriction, after passing some eccentrics and a gour pool swung back into large passage again.

The stream re-appeared in the floor and high up they passed a cross passage with curtains well out of reach of muddy fingers, finally coming to a third choke.  Clarke and Aslett came back wet and tired but they had found the way on.  It was September 20th after a week of heavy rain that Clarke, Leyman and I went down. We crawled into the Braithwaite/Murrell route to find only 2ins of airspace in the tightest spot.  Discretion, we decided, was a good excuse for not getting wet.  We retraced our steps and climbed over the boulders under the sagging roof and carefully searched every cranny.  A hole beneath a crumbly shaleband, whilst looking most unnattactive, proved to lead to the shattered zone between the first and second boulder chokes.  After some adjustment, this new route looked a lot safer and was unnaffected by the level of the water.

We pushed on down to the third choke and scrambled up an opening behind the calcite flow on the right.  It went easily, avoiding any loose blocks.  Before us stretched a large chamber, the end of which we were unable to see (Great Hall).  We carried on, meeting the stream again.  Further on, a spout of water issued from a 6in hole in the wall (Fire Hydrant).  We carried on until everything became covered in a sticky mud, the passage became narrower and the stream finally disappeared in a most unattractive sump.

The main passage in Pant Mawr is quite large, 30ft wide and 20ft high or more.  The stream at the end disappears down a miserable little crack filled with mud.  I have long held a theory that the water that enters Pant Mawr Pot originally flowed underground towards the Swansea Valley and possibly there was a connection with Ogof Ffynnon Ddu.  Having read Dr. North’s book ‘The River Scenery at the head of the Vale of Neath’, I wondered if the Neath Valley which, he says, was cut down very quickly in recent geological times,  captured this water underground  and changed its flow towards the Neath Valley.  It was this theory that set me wondering if the water that went to ground into Bridge Cave, higher up the Neath Valley might actually resurge in the Mellte Valley somewhere near Porth yr Ogof.  There is no natural law which requires an underground river to stay in its own valley.  In dry weather the Neath Valley is dry between Bridge Cave and the Pant Mawr risings.  It was this thought that prompted me to put some fluorescein in the water flowing into Bridge Cave.  In the end, my theory was proved wrong; the fluorescein came out in the same valley in the same risings as the stream from Pant Mawr,  proving that the Bridge Cave water stayed in the Neath Valley.  In actual fact there are still people who say that that Bridge Cave water divides underground, some staying in the Neath and some resurging just north of Porth y Ogof.  This could possibly happen in flood conditions.  When I did my test, I saw the dyed water coming out in the Neath but omitted to see if it was also coming out in the Mellte.  I think it would be most unlikely for an underground river to divide in this way, but it could be possible that there are two resurgences in time of flood.

Edited by Jem Rowland                                                       back to the top
23 March, 2009