Note that this is a re-print of the original publication, based on a scanned copy. During the process of converting the original paper copy to this electronic version, the original formatting, page layout and page numbers have been lost. All diagrams and surveys have been scanned from the original and are consequently of poor quality.
The Use of a Prismatic Compass as a Theodolite by MT Mills and BM Ellis
Beyond the First Mud Sump, Swildons Hole by MT Mills
Recent Developments in the Swildons Streamway by B Woodward
Published by the Shepton Mallet Caving Club
The Mineries, Wells Road, Priddy, Wells, Somerset, BA5 3AU
I will not make the usual apologies for the delay in producing this publication, suffice to say that it is somewhat fortunate in that we have had an extended Autumn this year.
In this issue there is an article concerned with surveying, pointing out that had we known then what is being inferred we may have been saved considerable work.
This is followed by the 'complete works' on the First Mud Sump, Swildon's Hole, in which it seems most of the past and present active club members took part at some stage or other in the considerable lengthy period of exploration.
The Swildon's Streamway is the next area of development where the accent has been on 'by-passing' sumps, by the CDG. The author also is a club member. He has apologised to me in advance for the accuracy of his sketches but apparently without some kind of sustained 'spiritual sustenance' down at Sump Twelve a kind of narcosis sets in, and anyone who wishes to improve or dispute has got a long way to go!
And finally a commercial. The Occasional Paper No.6 on the club's Icelandic Expedition in 1970 concerned only with the aspects of organisation, has at last been published. It will only cost you 25p exclusive of postage, which is a further 5½p. Copies may be obtained either from me or Bryan Ellis.
I gather that the Scientific Report of the Expedition is at the printers and should be available shortly.
A description of a simple cave theodolite was published in a recent issue of the SMCC Journal, together with some data on its accuracy in use (1). This instrument was the one used by members of the club for making the survey of Raufarholshellir lava cave in Iceland. Since going to this trouble we have realised that in fact it is not necessary to modify the Survey Unit (nor construct a special cave theodolite) for use when magnetic anomalies cause surveying by compass to become inaccurate; the prismatic compass itself can be used as a theodolite.
Provided that one is considering natural magnetic interference or stationary artificial sources of interference (or a combination of these two) then the influence on a stationary compass will be the same irrespective of the direction in which the compass is pointing. Therefore, although a compass reading will not give a true bearing with respect to the magnetic north pole, the angular difference between compass readings taken along two lines of sight will not be affected by the anomaly. It is important to bear in mind that this is not true if the source of the anomaly moves between making the two readings so it is still necessary to ensure that the surveyor does not have large magnetic objects in his pocket, for example, while surveying. If forward and backward compass readings are taken at each survey station, by simply subtracting one reading from the other the included angle between the two survey lines is obtained. It should be remembered that in order to obtain the clockwise included angle the reading made in the backward direction must be subtracted from the forward reading, and not the other way round; if the former is larger than the latter, 360° should be added to the forward reading. There are inherent disadvantages in making a theodolite traverse but in certain circumstances the use of the compass in this manner may well give more accurate results than using it to obtain a bearing with respect to the local magnetic north.
During the making of the survey of Raufarholshellir, four experimental closed traverses were made when both cave theodolite and compass (forward and backward) readings were taken. From these it is possible to calculate the traverse misclosures both for using the cave theodolite with a six inch diameter horizontal scale, and for using the prismatic compass as a theodolite. The results are shown in Table 1. Also given in the previous paper was a table of results showing the spread of readings obtained with the compass and the cave theodolite when measuring the same included angle. These results can be summarised here by stating that the standard deviation for the readings was 0.86° for the cave theodolite, and 0.37° for the prismatic compass; the mean results were 248.0° and 248.6° respectively.
Table 1 – Traverse Misclosures
Unfortunately we did not think to measure the same angle with the Cooke, Troughton and Simms theodolite as a knowledge of the correct value would have given an indication of the relative accuracy additional to the indication of precision given by the standard deviations. However, taking these results together with the traverse misclosures given in Table 1, it will be seen that the accuracy of the two methods is similar while the precision is better with the prismatic compass. It must be emphasised that these compass readings were taken with a tripod mounted instrument that had been modified to include a larger prism. Without the larger prism the precision would be lower, and without a tripod the readings would be valueless unless extreme care was taken to minimise station position error.
The use of a compass as a theodolite involves an extra step in the calculations to determine the bearing of the second survey leg relative to the first. To save the surveyor frantically searching his memory for long forgotten geometry, the bearing can be calculated by using the following formula:
bearing of second line = 180° + (forward theodolite reading) + (bearing of first line) - (backward theodolite reading).
If necessary, 360° or 720° should be subtracted from the answer to give a bearing that lies between 0° and 360°. This formula is applicable if the horizontal scale of the 'theodolite' is marked in a clockwise direction; if it is marked anti-clockwise then the forward reading is subtracted from the one in the backward direction. When the bearing has been obtained the station co-ordinates can be calculated in the usual manner and additional errors will not be introduced by inaccurate plotting of the theodolite traverse with a protractor and scale.
(1) Ellis, BM. A Simple Cave Theodolite. SMCC. Jnl., 4(10), pp8-14.
MT Mills and BM Ellis, January 1971.
On the 25th of January 1953, Phil Davies, Keith Evans, Willie Stanton, Luke Devenish and Howard Kenney attacked the Blasted Boss which was at that time the extent of the known cave in this direction. After a 'bang' Stanton and Kenney passed the boss and walked through the first hundred feet or so of St. Pauls. The following day Stanton and Kenney returned to the scene with Don Thompson and Oliver Lloyd to continue the exploration. This exploration was continued on the 1st of March 1953 and two weeks later was followed to its bitter end at the Second Mud Sump.
It was not until November 1953 that the first efforts were made to break out of the series (1) at the First Mud Sump, where at that time the roof came down to within a few inches of a rough sandy floor and a trickle of water flowed along a channel adjoining the left hand wall. Initially the dig was straightforward, the water stayed in its channel and a crawl was easily cut for several feet through the sand, which was getting even closer to the roof. The little stream then invaded the dig, made this very muddy and little further was made on that occasion. Between November 1953 and March 1954 three further trips to the site were made but on no occasion despite digging and bailing efforts was that point reached on the first trip significantly passed.
Oliver Wells was the instigator of these earliest abortive attempts at the First Mud Sump with members mainly from CUCC (2), and on meeting Dennis Kemp a joint assault was arranged for 5th/6th March 1955 at the Second Mud Sump. Bailing this sump was successful and on the 6th of March Eva Waller, Keith Chambers and Oliver Wells passed it to explore as far as Shatter Pot.
Following the earliest attempt it appears that Mike Thornpson and Bob Pyke were the next to investigate the site (3) and on the 22nd of August 1959 some two hours were spent bailing at the site resulting in extending the passage by six feet. The conclusion reached was that further work would require not only bailing but digging out the soft mud floor.
Derek Ford (4) points out that contemporary with the main stream of the 'first cave' but quite independent of its source and destination were a series of little phreatic tubes (termed chipolatas) descending bedding planes in the fault zone converging or diverging on each other, and that those in St. Pauls' converged on the First Mud Sump. During this development of the cave the stream from Swildon's I through St. Pauls' continued to flow to Shatter Passage until it was diverted and the old 'chipolata' route was re-opened to turn water into the First Mud Sump and thence by a route unknown to discharge into II downstream of Duck 1. The water level fell to 470 feet making the Mud Sumps true, watery, sump areas.
Later the route of the main stream through the First Mud Sump was abandoned for the present course from Tratman's Temple to Sump 1. The passage in the First Mud Sump route became backwater ponds, occasionally taking flood surcharge that the new route could not take. The largest and longest lived backwater pond was Shatter Passage, which spilled over to the Second Mud Sump and the water ultimately joined the then main stream at the First Mud Sump.
Initial Work in 1965
Returning from a trip to South East Inlet on a 14th of February 1965 Bill Tolfree and myself had a good look at the First Mud Sump (6) with a view to bailing it. Two weeks later on the 27th of February we were joined by Paul Allen, Steve Causer, Roger Biddle and Bob Gannicot and carried a semi-rotary pump and a length of loose pipe into the cave. The pump was rawl-bolted to the wall and the hose laid up the slope towards the Second Mud Sump. Mud dams were constructed across the passage and the water in the sump was pumped up to this reservoir revealing the prospect of a very muddy dig closing down at that time after about twenty feet (7).
Oliver Wells (2) had in 1953-4 concluded that the water must be put far enough away to prevent it returning by an alternative route, and had also tried using a stirrup pump which proved useless. Our first attempt with the semi-rotary pump appeared to indicate that this was very much more efficient (5).
On the 13th of March 1965 Barry Lane and Bob Craig re-visited the dig and pumped away for a couple of hours without any apparent reduction in water level, at which point Barry noticed a breach in the mud dam (only the first of many to come). At this point I joined them at the dig and the pump proceeded to give up the ghost (8). A week later Bob Craig, Pete Cousins and Roger Biddle soon came to the conclusion that it was easier and quicker to bail the sump dry using buckets rather than the pump (considerable difficulty was found in priming the pump due to the silt in the water). A great deal of water was present but about three feet further was dug into the sump in soft mud, before both the main dam and a subsidiary dam constructed behind a large boulder in the floor part way into the sump were filled to over-flowing. On this occasion also the small stream that flows down the East Wall of the main passage about a hundred feet back towards the Blasted Boss was also dammed back to prevent it adding to the quantity of water in the dig. On completion of the days digging when all the dams were released the torrent of water flowed into the sump which filled up and the water level quickly dropped to its normal level (9). Although this fact was noted at the time it was perhaps not fully appreciated that this tended to indicate that the mud choking the sump was of only relatively short length.
It was realised that to make further progress a more reliable and permanent form of dam was going to be required and so a hundred-weight of cement was broken down into seven used one gallon paint tins. The first four tins were taken down the cave by Ray Mansfield and myself on a midnight trip on the 4th of July 1965 (10). Barry Lane carried a further two tins to the sump the following day (11), and the final tin was taken in by Pete Smith, Bill Watkins and Roger Biddle the following Saturday, when under Pete's direction and benefiting from his experience, in a couple of hours the cement was mixed with mud and water and using some of the tins in place of rocks the first permanent dam was constructed (12). The following Saturday I spent some hours alone and succeeded in bailing all the water out of the sump and into the lake formed by the new dam (13). With all the water bailed out everything looked fine for the 'morrow and it was decided that the proposed club trip to Cuthbert's should be abandoned in favour of further work at the sump and thus Ken Dawe, John Illes, Bryan Ellis, Roy Taylor, Fred Davies and myself arrived at the sump only to find that overnight the dam had leaked most of the bailed water back into the sump. It was again bailed dry, further liquid mud was excavated and a cross rift reached. This cross rift formed a useful air space and much needed headroom, when Fred Davies probed on into the mud of the sump feet first but was unable to find any sign of the roof rising (14).
Thus ended the initial work at the mud sump, and the site already had a reputation for being a very uncomfortable dig and so not unnaturally none of us appeared to be keen to restart digging and the passage of years was necessary before anyone would readily contemplate another trip.
Intermittent Work 1967-70
There was a trip by Roger Haskett sometime in late December 1966 or early in January 1967 and the sump was found to be full to the brim. The conclusion was that a longer and higher dam was required to provide the capacity for all the water present (15).
On the 20th of August 1967, I had intended to ferry a further six tins containing together ¾ cwt of cement to the sump as a forerunner to a later trip to use this in improving the dam. However, luckily (and the sort of luck that one does not often get) I met on 'The Green' a chap I knew who was taking a party of four through via Blue Pencil to IV, and what was more they were willing to carry the tins. Having thus saved much time, I utilised this in stripping away the mud and stones of previous dams to the left of the existing dam on the side distant from the mud sump. After draining the pool this side of the dam into the sump and building sufficient temporary dams to divert water flowing into the sump away from the site of the works, I then built a dry stone backing along this face and after mixing the cement with mud and sand, faced this with a two inch layer of same (16).
The next trip was on the 31st of March 1968 when Bob Craig, Alan Butcher and myself rapidly bailed the sump only to discover, when we had almost drained the sump, a sizeable leak in the dam. This was repaired before we left the cave (17). A week later Bob Craig, Phil Romford, Alan Butcher and John Norris bailed until another leak in the dam was found, however they found that they could bail faster than the water was leaking out, but found that the dam was full to the brim and there was still some water in the sump. The main purpose of the dam had been to contain water but it also had a subsidiary function in preventing further silt being washed into the sump by the small seasonal stream / trickle that flows down the East Wall of the main passage about a hundred feet back towards the Blasted Boss. The side effect of this silt trapping was of course to reduce the capacity of the dam; and so they made a start in digging out the silt but made little impression with the only tools available, the gallon paint tins (18). The following Saturday, Alan Butcher, Bob Craig and Bob Cross using shovels, removed most of the accumulated silt and the small dam constructed in March 1965, about a hundred feet upstream of the main dam, was made permanent by using cement (19). The next day the same three with Roger Haskett bailed the sump dry but found that they were insufficient in number to dig efficiently, and suggested a further dam which would involve a much larger construction, which required building slightly upstream from the existing main dam (20).
On Christmas Eve 1969, Alan Butcher, Pete Bowler and myself commenced again digging the six to eight inches of mud and silt which had accumulated behind the main dam during the previous eighteen months or so (21). Three days later with Bob Craig, the same three continued excavating the silt and new pipes were put into both of the dams. When most of the work was completed we were joined by Dave Yeandle and Dick Wickins. Most return trips to the surface were uneventful apart from 'wheegie-jumping' in the streamway, however, on this occasion we noted a solitary young lady shivering at the foot of the 'Twenty'. Upon enquiry we learnt that this young lady, a friend of a Wessex member, had been unable, through exhaustion we assume, to climb the ladder and her young knight in armour had gone out for assistance. Finding ourselves in the unusual position of being a rescue team coming from within the cave we assisted the young lady as far as the new 'Forty' before encountering her expected rescuers to whom we landed her over (22). Bob Craig and myself on the 16th of January 1970 made a quick Friday evening trip when the cave was nearly under flood conditions to finish excavating the silt from behind the main dam (23). The following Saturday with the cave still under high water conditions Bob Craig, Derek Harding and Phil Romford bailed out the sump and excavated a trench to assist bailing but found conditions too wet for digging at the face (24). Next day Bob Craig and Dick Tye with two more paint tins of cement re-sited and rebuilt the small dam constructed about a hundred feet upstream of the main dam (25).
Despite the number of trips to the sump during this period, in fact a concerted attack had not taken place and most of the time had been spent in repairing dams and the like.
Final Assault 1971
Almost a year after the last trip, on the 2nd of January 1971, Dick Tye, Dave Gillespie, Steve Summerhayes, Alan Butcher and myself found the dig had silted up considerably when the water was bailed out. A start was made on removing this silt, which being liquid mud was difficult to stack and 50 ponds were formed using boulders as edging, and even cement was sprinkled over the surface to aid drying out. It soon became apparent that six inches of extra height was required on the main dam to increase its capacity and that a smaller permanent dam was required part way into the sump. A leak still existed in the side of the main dam and was noted as requiring attention (26). A fortnight later Bob Mehew, Alan Butcher and Graham Wilton Jones took down a ¼ cwt of cement and patched the leak in the main dam and added the necessary six inches of extra height to the top of the main dam (27).
On the 6th of February Alan Butcher and myself took down some more cement (as appears to be the norm on Mendip nowadays) and repaired a small hole in the side of the main dam before commencing bailing. A further leak was apparent and so the water was drained back into the sump after the leak had been traced to a minute hole, which we plugged before we left (28). A week later a party comprising Brian and Janet Woodward, Bob Mehew, Steve Summerhayes, Alan Butcher and myself bailed the dig sufficiently to permit about one third of the small dam, part way into the sump to be constructed with cement which we had carried down. (29). Steve Summerhayes, Alan Butcher and Bob Mehew on the 6th of March, repaired yet another small hole in the main dam before continuing work on the small dam, part way into the sump (30). The following week the same three people together with Janet Woodward and myself continued work on this dam building in a pipe as work progressed (31). A week later, Alan Butcher, Bob Craig and myself completed this dam, with cement taken down with us (32).
With the new dam completed part way into the sump, close to the large boulder which had formed the site of a similar mud dam, built on the trip exactly six years earlier to the day, and convinced that we had now plugged every leak in the main dam, we were in a position to start digging – which at that time was a relatively attractive proposition, after so many trips merely working on the dams.
Thus the following week, the 27th of March, a party comprising Bob Craig, Steve Summerhayes, Alan Butcher, Bob Mehew and myself found ourselves once more at the sump. The procedure when digging was to drain any water behind the main dam into the sump because, as noted earlier, this would drain away and the water in the sump would drop rapidly to its normal level. Whilst waiting for the water level to drop on earlier trips the sound of trickling water had been heard and after having convinced ourselves that this was not coming from somewhere in the sump it was eventually traced by following the main passage towards Shatter Pot and at the top of the first rise where once we had used the passage as a reservoir, entering a descending low passage on the right the noise was found to be coming from a small hole in the floor. If this passage is pursued one soon reaches a large pool of water and beyond this on Stanton's master plan of the cave the passage is shown by broken lines.
The next stage when digging, after the main dam had been plugged, was for two people to start bailing, using buckets, the water between the two dams. Originally this had been easier when the dam was only about 2½ feet high on the far side, but now it was 3 feet or thereabouts and with the roof only about 18 inches wide above the dam it was much more difficult. As soon as the two bailers began to flag two more would take over. Then when the water between the dams was getting low one person would climb over the smaller dam beyond and sit up to their chest in water bailing this into the area between the two dams and so keeping the other two bailers working. The sound and rhythm of buckets of water being poured over the dams must have been quite impressive when heard, while approaching from the Blasted Boss. On several occasions other parties of cavers mistakenly thinking we were bailng the Second Mud Sump, would dash into the lake behind the main dam to point out that we were bailing in the wrong place, only to be greeted with blank replies of "Eh! What?" This led them to put more effort into endeavouring to convince us of our mistake, and even on one occasion we were temporarily physically restrained from continuing bailing.
When the water level beyond the smaller dam was lowered loud glooping noises were produced when the cross rift reached in 1965 had its airspace broken. With the water lower bailing would be reduced to scooping up a pool of water on the floor and then another person would join the line so that the person in front could go further into the sump where the water was deeper and then pass the buckets back to be emptied over the smaller dam into the space between this and the main dam. As digging progressed further another and then a fourth would climb over the smaller dam to join the bucket chain.
On this particular occasion 6 inches of liquid mud was removed from the floor of the sump and digging was started at the cross rift last reached on the 18th of July 1965 and about 5 feet of progress was made beyond (35). All the liquid mud removed was passed back in the buckets and tipped over the main dam into the lake beyond – it was found impossible to stack or dump this on the sump side of the main dam and to transport it across the lake was impracticable, though it would have been ideal. The only disadvantage of tipping the spoil in the pool was that once again the capacity of the dam was reduced.
Breakthrough and Exploration
One week later on the 4th of April, Alan Butcher, Bob Craig and myself together with Steve Boniwell and Chris Wood and their respective parties bailed the sump dry again as per usual and found the main dam to be nearly filled. Bill Watkins joined us as Steve Boniwell and Chris Wood with parties left. A considerable amount of liquid mud was again removed until both dams were brimming full and temporary mud and rock extensions had to be made to increase their height. As we dug further into the sump water was found to be gushing up through the mud at the farthest point into the sump. We were digging following along beneath the roof which was found to rise and after some more digging an air space was soon encountered, This point was but a few feet beyond that distance probed on the 18th of July 1965. The opening was enlarged and Alan Butcher ducked under the lip of the roof to find himself looking up a low crawl of mud up a 40° slope with an opening visible at the top about 15 feet beyond. Liquid mud was flowing down the slope and threatening to cut off his retreat, but rather than remove the vast amount of spoil accumulated on this side it was decided to force a way through after clearing some of the threatening mud. Floundering his way up the slope Alan Butcher found himself in a small chamber / passage which went about 30 feet before it became too tight at which point the floor was of stalled boulders, but the airspace above this was too narrow to follow and it appeared that we would have to start digging again. Before he returned he excavated a channel in the floor in order to aid drainage, as the far side was the highest point in the sump. Finally all the spoil excavated was removed before releasing some of the water after a seven hour trip (34).
The following Saturday Bob Mehew, Alan Butcher, Steve Summerhayes and myself restricted ourselves to merely removing the accumulated spoil from between the two dams, after draining the main dam from the floor of the pool behind this. Finally the temporary top to the main dam was made permanent with cement mortar providing a limited squeeze between this and the roof (35). The following day the same four together with Bob Craig took down various odd items including polythene sacks and a 5 foot broad plank of wood. These items were used to form a mobile temporary dam near the working face to aid bailing of liquid mud. After two hours of bailing Bob Craig went through to inspect the scene and shortly afterwards announced that there was a small narrow passage high in the left wall at the point where the main passage dropped in height and was too low to follow. I went through to join him and entered the new passage. It was about 2 feet high and 10 inches wide at its widest point and there was a hole in the floor just after one leaves the main passage which connected back to this at ground level. There were a couple of straws in the roof and after about 15 feet the passage bore slightly right at a wider section and then continued on through a tighter section. My light did not reveal what happened to this passage and so taking off my Nife cell I edged my way along this with its rough walls and floor as well as some crystal pools. Beyond the tight section the passage increased to a comfortable width and then dropped 2 feet into some crystal lined pools. At this point I thought that this was the far side of a sump connecting back through to that at the bottom of the descending low passage on the right following the main passage from the Mud Sump towards Shatter Pot where we had located our sound of running water. However, I thought, it did at least provide me with room to turn round. After yelling back to the others, I crawled across the pools and followed the low passage which revealed itself downhill, through some more pools, the water displaced running ahead of me and over a drop; a pitch perhaps I thought doubtfully. On reaching a parting of the ways I took the right hand way around and round the pitch to be in fact a 3 foot drop. Here one could almost stand up. Ten feet further on I was hailed by Bob Craig who advised me that the dams were full and suggested that I returned. Taking a quick look along the low passage going on, it appeared to veer to the left and increase slightly in size (36).
On the return journey I estimated, by counting body-lengths that the new passage was about 150 feet long. During my absence Ray Mansfield had arrived and all had been through the sump to look at the first section of passage. All were surprised that Alan Butcher had overlooked this passage the previous week when he had been the first through the sump – he had not even mentioned its' existence – apparently he had noted same but dismissed it as being too tight. If any name was required for this passage, it should be called Myopia Passage!
The following Saturday, April the 17th, Bob Craig, Steve Summerhayes and Tim Large went down early taking with them a 180 foot length of black polythene agricultural hose. Due to the rigidity of this it could not be coiled in anything less than about a 6 foot diameter coil. Since it could not be taken down the cave in this state it was unrolled and taken down 'in length' which provided some fun. Picture, if you can, a party at the foot of the 6 foot who gave way to a party of only three. Down jumped the leader and walked off downstream towing the hose, when he was out of sight the middle-man jumped down and repeated the incident. There was of course a slight delay while the leader descended the 'Twenty'. With the fun over the sump was bailed during which time Bob Mehew, Alan Butcher and myself joined the other three. I then took through half the length of pipe, and Tim Large took the other half, both ends being pushed down the slope where the main passage continued but was too low to follow. Both pipes were then connected to the main dam and the water released through the pipes. With the others watching the dam and pipes, Bob Mehew and I entered the small side passage with the intention of following this to its' end. At the point where I had turned back the previous weekend, there was now a muddy stream emerging from a small crack on the right and this was obviously where the water piped through the sump re-joined the passage.
Following the stream it turned left at a pool and low arch, and there was on the left a small side passage going back up in the direction from which we had come, however, we followed the stream across an inclined slab floor with the stream at its foot on the right. The passage veered right and steeply down with a rock slab like floor with the roof height increased to 4 feet or so and the width to 6 feet. This looked more hopeful: at the bottom going left through a high short trench section with the stream among the boulders, this passage was of walking height, meandering back to the right and then sharp right and then sharp left down a rocky floor, with the roof dropping in height to a sump. While I crawled down to examine this, Bob followed an inclined oxbow on the right to land on a silt bank on the other side of the sump. Probing the sump it appeared to be at least 1 foot high below the water, but we were not convinced that this was in fact a permanent sump, as a stream was now flowing into it, and we had not had the benefit of seeing it without the stream. Digging and/or bailing this sump would be very awkward due to the tight nature of the passage for getting digging tools through and the limited room for spoil and water storage. A slight draught was thought to be noticeable from a very small stalled corner to the right of the pool.
On the return journey we estimated that the total length of the passage was 350 feet, and Bob crawled into the side passage previously noted. This went about 12 feet rising and turning sharp left where it rapidly narrowed, but might be pushed by a very small person, and carried a small trickle of clean water. Meanwhile Bob Craig and Tim Large had gone down the descending low passage on the right, following the Mud Sump towards Shatter Pot, where we had previously traced our sound of running water, and could hear us quite plainly taking to each other in the vicinity of this small side passage. When we returned to the dams, those who had come in on the earlier party were cold and eager to get moving to the surface having been underground for about 8½ hours altogether. The water behind the main dam had taken about three hours to drain away (37).
On the 22nd of May a party, comprising Bob Mehew, Steve Summerhayes, Bob Craig and myself, after bailing the sump with the pipes still connected, proceeded on the slow journey to the new sump with a view to connecting a survey there and working our way out. No difficulty was encountered by anyone in negotiating the tight section in the passage. During the course of surveying, Ray Mansfield called to see if his assistance was required. Not unnaturally the speed of surveying decreased considerably towards the end of the 6½ hours underground when we had to survey back through the Mud Sump (38).
The survey was carried out by 'leap-frogging' using a Suunto KB 14/360 compass and PM 5/360 PC clinometer. Both were graduated in degree divisions and due to the nature of the passage and surveying conditions the instruments were only read to the nearest degree. Similarly both instruments were hand held, although care was taken to minimise errors due to station movement – the use of a tripod mounted instrument would have reduced the possibility of this though increased the problems by taxing the time and patience of the surveyors. The 50 feet 'Fibron' tape was read to the nearest 0.1 feet, and passage details were taken at every station and at intermediate points where necessary due to a significant change in the passage detail.
The figures were reduced to co-ordinates using a Four Figure Logarithm Table, and the survey accompanying this article was plotted from these co-ordinates. The total length of passage from the main dam was 280 feet (approx.), with 20 survey stations and an average leg length of 12.5 feet (max. 20.6 feet, min. 3.5 feet). Roof heights varied from 1 to 10 feet. The total fall in the passage is about 37 feet with a level of -27.6 feet. (approx.) O.D. at the final sump - this figure may be +/- 1 foot due to the fact that the exact point of the level datum of 461.3 feet shown on Stanton's master plan of Swildon's Hole at the previous limit of the passage at the Mud Sump was not known.
Figure 1 – Plan Survey of Swildon’s Hole beyond the Mud Sump
Figure 2 – Elevation Survey of Swildon’s Hole beyond the Mud Sump
Figure 3 – Survey showing new passage in relation to Stanton's Master Survey
As already indicated the prospect of bailing and/or digging the new sump at the end of the new passage is not likely to be easy due to limited storage space and the difficulty of reaching the sump through the narrow passage, particularly carrying digging implements. Therefore if Ford's geological theory is to be proved and another possible round trip added to the Swildon's complex it will probably be easier to start digging from the Swildon's II end. Just downstream about 50 feet or so from Duck I high up about 20 feet above the stream, is a small passage which goes about 20 feet or so and shows signs of carrying a small muddy stream at times. This would appear to be the likely point where the Mud Sump joins Swildon's II though as far as is known the connection has not yet been proved using a water tracer.
(1) Wells, OC. A History of the Exploration of Swildon's Hole, published privately (Pennsylvania, July 1960) pp.6-2, 6-3.
(2) Wells, OC. Saint Paul's Series Mud Sumps, Swildon's Hole, WCC Jnl. 3 (50) p.11, (April 1955).
(3) SMCC Hut Log 3 p.56, entry 22 Aug. 1959, republished in SMCC Occ. Pap. (5), pp.49-50, (April 1970).
(4) Ford, D. The Sequence of Development in Swildon's Hole. WCC Jnl. 3 (99), pp.199, 202-203.
(5) WCC Jnl. 8 (100) p.223 (March 1965).
(6) SMCC Hut Log 5 p.4, entry 14 Feb 1965.
(7) SMCC Hut Log 5 p.6, entry 27 Feb 1965.
(8) SMCC Hut Log 5 p.8, entry 13 March 1965.
(9) SMCC Hut Log 5 pp.12-13, entry 20 March 1965.
(10) SMCC Hut Log 5 p.23, entry 4 July 1965.
(11) SMCC Hut Log 5 p.24, entry 5 July 1965.
(12) SMCC Hut Log 5 p.26, entry 11 July 1965.
(13) SMCC Hut Log 5 p.28, entry 17 July 1965.
(14) SMCC Hut Log 5 p.28, entry 18 July 1965.
(15) SMCC Hut Log 5 p.78, entry undated.
(16) SMCC Hut Log 5 p.107, entry 20 Aug 1967.
(17) SMCC Hut Log 5 p.125, entry 31 March 1968.
(18) SMCC Hut Log 5 pp.128-129, entry 7 April 1968.
(19) SMCC Hut Log 5 p.129, entry 12 April 1968.
(20) SMCC Hut Log 5 p.130, entry 13 April 1968.
(21) SMCC Hut Log 6 p.165, entry 24 Dec 1969.
(22) SMCC Hut Log 6 p.165, entry 27 Dec 1969.
(23) SMCC Hut Log 6 p.176, entry 16 Jan 1970.
(24) SMCC Hut Log 6 p.179, entry 24 Jan 1970.
(25) SMCC Hut Log 6 p.180, entry 25 Jan 1970.
(26) SMCC Hut Log 7 pp.91-92, entry 2 Jan 1971.
(27) SMCC Hut Log 7 p.94, entry 16 Jan 1971.
(28) SMCC Hut Log 7 pp.100-101, entry 6 Feb 1971.
(29) SMCC Hut Log 7 pp.102-103, entry 13 Feb 1971.
(30) SMCC Hut Log 7 p.105, entry 6 March 1971
(31) SMCC Hut Log 7 p.105, entry 13 March 1971.
(32) SMCC Hut Log 7 pp.107-108, entry 20 March 1971.
(33) SMCC Hut Log 7 pp.111-112, entry 27 March 1971.
(34) SMCC Hut Log 7 pp.115-116, entry 4 April 1971.
(35) SMCC Hut Log 7 pp.119-120, entry 10 April 1971.
(36) SMCC Hut Log 7 pp.120-121, entry 11 April 1971.
(37) SMCC Hut Log 7 pp.121-124, entry 17 April 1971.
(38) SMCC Hut Log 7 p.132, entry 22 May 1971.
MT Mills, September 1971
Until July 1971, sump 6 marked the effective end of Swildon's Hole as far as free diving was concerned. This situation had prevailed since 1961 when CDG members dug away the gravel bank on the far side of sump 5 to make this sump into a low duck. Since then, sporadic attempts to by-pass sump 6 have been made without a great deal of success.
By climbing the steep slope to the left of sump 6, a passage is entered which forks after about 20 feet. The right hand passage develops into a rift about 20 feet high which passes over sump 6, this passage however becomes too tight and further progress is prevented. The left hand fork, which initially goes in the opposite direction to sump 6 and upstream, eventually passes over the 6 streamway and turns back downstream. About 30-40 feet from the original end of this passage a small stream enters from the right, flows through a squeeze and into a small chamber where it ended in a tight sump.
In September 1970, CDG members started a systematic examination of all the passages downstream of sump 4. The passage described above was entered by Geoff Phillips and Brian Woodward and after poking about in the slurry of gravel and water which constituted the sump, they returned to the main streamway and proceeded to Swildons 7. In 7, it was noticed that the inlet 20 feet downstream of sump 6 was a delicate shade of brown. This crude dye test proved that an alternative route to Swildon's 7 existed which might provide access to 7 for 'non-divers' if it could be opened up. The inlet in 7 ended after a 30 foot crawl in a sump pool, this was bailed until the water level was down by about 1 foot but the sump still remained in its virgin condition.
December 1970 saw Martin Webster and Aubrey Newport digging on the 7 side of this sump while Colin Priddle and Brian Woodward attacked it from the 6 side. After about an hour's digging and bailng the sump started to gurgle and soon an aural connection between 6 and 7 was made. The passage was badly silted up and it was not possible to get through the squeeze. The obvious answer was to dig a trench on the downstream side so as to lower the sump permanently, the floor of the sump could then be dug out to make it caveable. On July 24th, Phil Collett, Tony Jarrett, Martin Webster and Brian Woodward eventually enlarged the passage to Collett size. Martin had the dubious pleasure of being the first person to enter Swildon's 7 via the bypass and on August 7th Pete Moody was the first caver to reach Swildon's 7 without diving gear. The trench was not deep enough and the passage still required bailng from the downstream side, this however has since been remedied and the bypass is now permanently open to cavers who are capable of freediving sump 4.
Pleased with the success of bypassing sump 6, attention was turned to sump 7. It had been known for some time that an aural connection existed over sump 7 and in May 1971, Martin Webster, Phil Collett, Tony Giles and Bob Churcher made an aural, visual, and finally (wait for it) physical contact between 7 and 8 via a small airspace to the left of the sump. However, they were unable to get through the passage.
On September 25th, Phil Collett, Tony Giles, Brian Woodward (diving) plus Pete Moody and Rob Harper (freediving) went to Swildon's 7 with the intention of opening up the bypass to sump 7 for non-divers. The water level was very low and two or three small airspaces could be seen to the left of the sump. Tony managed to negotiate the largest of these, which was nose shaped and about 3 inches high, this gave access to an airspace about 15 inches high. The way on led over a boulder covered with a thick layer of mud which effectively blocked further progress. At this point Phil and Brian dived sump 7, Phil gave Tony a hand to dig out the mud while Brian dropped the water level in the sump by digging away at the gravel bank on the far side of sump 7. After about 20 minutes, Tony was able to squeeze over the boulder and so enter Swildon's 8, closely followed by Pete and Rob, everyone being slightly surprised at the ease in which the bypass was made. After a quick tour of 8 and 9 (sump 8 can be bypassed) everyone returned to 6. Tony, Pete, Rob and Phil using the bypass, which, like the sump 6 bypass was the size of a thin Collett. Under high water conditions this route will be sumped and not freediveable, and in order to overcome this the boulder was removed with 2lbs of persuasion (At a later date we hope to enlarge the first small airspace as this is the key to free access to 8 and 9 for 'non-divers').
The bypasses to sumps 6 and 7 have now opened up the major part of the known Swildon's streamway to non-divers, the remaining distance between sump 9 and 12 being about 250 feet. A thorough examination of 8 and 9 may bring to light a by-pass to sump 9 which at the moment appears to be a rather uncompromising problem.
Figure 4 – Sketch Surveys of various sump bypass passage
Over the past year attempts have been made to bypass sump 12. For those who are not familiar with the situation, sump 12 descends to a depth of about 40 feet, at an angle of about 40° down the dip. At the bottom of the sump a tight squeeze gives access to an ascending rift which eventually becomes too tight for further progress. A number of people have reached this point and all agree that the prospects of diving to Swildon's 13 are remote.
Two tight passages pass over sump 12 and the right hand one of these has been the site of recent efforts to bypass the sump. This passage climbs steeply for about 25 feet and then follows the dip down at a 40° angle. The apex of the passage was originally too tight to get through and the whole of the descending section of the passage has been widened chemically. On August 7th, Martin Webster and Ken James had a trip to 12 to examine the effects of the last bang and were able to get down to the water levels again. The passage (12a) ends in a sump pool which is probably the continuation of the underwater rift which can be ascended for some distance in sump 12. The sump pool has been dived but a shortage of line prevented a full investigation.
B Woodward, November 1971