Alum Pot

By Geo. T. Lowe

Last year the Annual Meeting of the Club was held at Horton-in-Ribblesdale, and of the twenty-five men who attended, seventeen decided to participate in the descent of Alum Pot, the most interesting of the numerous chasms in the neighbourhood. The fact that the expedition was under the able leadership of our more experienced climbers and cave explorers accounted for this unanimity.

The ropes, ladders, and other miscellaneous tackle essential to the work had been sent up the previous day (Saturday, 27th September, 1902), for a preliminary examination of the two passages in Long Churn, one of which was known to lead into the northern end of Alum Pot. A survey of these was made and the water turned  by a barrier from its present course into the older passage. Along the watercourse thus freed a small party worked their way until they arrived at a large chasm. Unable to pass this a return was made, the barrier was broken through, and it was decided to use the traditional passage of Long Churn.

Alum Pot is mentioned by Hutton in “A Tour to the Caves in the environs of Ingleborough and Settle,” published in 1780.

The two earliest recorded attempts to descend Alum Pot took place in 1847, by a party of ten under Mr. Birkbeck and Mr. Metcalfe, and again in 1848; but they do not appear to have been successful. The first complete descent was made in 1870 by Mr. Birkbeck. This last expedition consisted of thirteen, three of whom were ladies. Beams were fixed across the middle of the mouth of the pot, and a cage worked from a windlass, operated by navvies employed on the Settle and Carlisle railway, was used. The party was lowered direct to the bed of the fissure, two hundred feet below, from whence they made their way to the bottom. The story is given in Boyd Dawkins’ book on Cave-hunting. In April, 1893, Geoffrey Hastings,

Dr. N. Collie, and A. E. Preston succeeded in reaching the bottom pool. Later Mr. Harold Dawson, of Bradford, failed on his first attempt; but he tried again and was successful.^[1]  On the 22nd July, 1900, T. S. Booth, W. Parsons, and W. Swithinbank reached the bottom.^[2]

In “Cave Hunting,” by Professor W. Boyd Dawkins, the name Helln is preferred to the ordinarily accepted Alum of the Ordnance Survey. The author connects “Helln” Pot with “Ællan” Pot or Mouth of Hell, and considers the name as a testimony to the awe with which the Angles regarded this huge hole. Alan, Hellan, and Hell, among others are various spellings of the name; but local pronunciation most nearly resembles Alumn or Alum, hence the latter form has been adopted in the present article.

Alum Pot is four miles from Horton, 1125 feet above sea level, on the eastern flank of Simon’s Fell, near Selside. Soon after eight o’clock on the morning of the 28th the men in scattered groups left the surface at Diccan Pot, and proceeded through the shallow stream down three short pitches, overlooking deep pools, each of which required careful traversing along the sides, and thence, the passage being now dry, to a long narrow cleft, at the bottom of which, at a depth of about twelve feet, the largest cavity in Long Churn was reached. Soon the voices of the pioneers were heard, and daylight was faintly visible through the great fissure which marks the outlet of Long Churn into the uppermost and biggest portion of the pot, about eighty feet below the surface and a little over one hundred yards in a direct line from Diccan Pot. A rope-ladder was firmly fixed at the top of an almost perpendicular gully, thirty feet high, broken on the west side by a small ledge, flanked with sharp edges of limestone. The life-line rendered assistance beyond this, and the explorer found himself on a narrow ledge over a shallow pool with several humps of rock showing above its surface. Beyond two huge fallen blocks open daylight appeared, and the vastness of Alum Pot could  be viewed from a kind of balcony, which together with the sides of the great pot, was covered with ferns and mosses combining to form a most beautiful picture.

The length of the surface opening is directly north and south, and the sun’s rays, now gathering strength, shone on the north end of the huge cavity through a cloud of spray produced by the falling waters of Alum Pot beck, which empties itself into the fissure at the south-west corner. The upper slopes were fringed with trees, whose waving branches sparkling with drops of spray and iridescent colours added to the charm of the weird scene. The vast walls of the pit illumined by the sun were transfigured and a charming effect produced.

A few interested spectators peered over the wall which surrounds the chasm and the small plantation that enables one to locate its situation from the surrounding hills. This wall is placed there for the protection of visitors, but it requires frequent repairs, as the stones are thrown by them into the pot to produce the awful clattering resulting from their bounding descent to the floor two hundred feet below. This practice is most exasperating to the farmer who has to keep the wall in repair. A caution was shouted against throwing stones, and the time was spent in surveying the surroundings.

It should be noticed in passing that great danger in pot-hole exploration may arise from falling stones dislodged by the men above; hence considerable care was exercised in clearing the ledges before the more difficult work commenced.

Below the balcony a rough and loose descent of about twenty feet leads down to the great terrace which runs round the sides, with the exception of a short length at the south end. The northern part of this terrace is curiously pitted with cup-shaped holes, containing stones and water, in which at flood time the grinding work is carried on, as is testified by the rounded form of the stones. In the middle a huge block has fallen, and rests at a steep angle against the other side of the fissure, forming a bridge across. At this point the hole is not more than ten feet wide. On the east side the ledge, covered with débris overgrow with moss, is from nine to twelve feet wide and fully exposed. The middle portion is slightly elevated opposite the bridge stone. On the west the ledge is almost flush with the wall of the pot; but this being considerably undercut an easy way to the bridge is afforded. Care is essential as the green carpet is slippery. From the east platform beyond the bridge a climb of about twenty feet down a crack leads to a lower narrow ledge. This had to be cleared of loose stones, as it was directly over the sheer wall down which the rope ladder was to be lowered. This ledge gradually diminishes north of the bridge and then disappears.

The ladder was hitched to two large pieces of rock at the top of the crack on the green platform. T. S. Booth, who had made the descent of the hole on a previous occasion, took charge of the life-line from the lower ledge, which supports the sloping stone bridge. For five hours he skilfully superintended the descent and ascent of the thirteen men who reached the bottom of the next stage at the foot of the sheer wall of rock. The hole is here very narrow, and the water falling from the south-western corner of the pot finds its way over fallen stones and down the rapidly sloping floor to a small cascade occupying the middle of a semicircular pitch of about ten feet. To the west the wall overhangs, and under this we crouched clear of any chance falling stone, interested spectators of the efforts of our friends on the ladder, until a sufficient number had gathered to continue the work. On the east a buttress nearly thirty feet high rose from the south corner close to the rope-ladder, and this was utilised by several men on the return; for rope-ladder climbing is not so easy as it appears from the descriptions in works of romance, where the lover lightly performs the impossible with a fair damsel hanging limply over one arm.

The leaves gently falling from the trees above caused us to wish we could emulate their easy downward course. Below the cascade the floor was heaped with small stones, kept back by a portion of one of the two beams originally used in the descent of 1870. These beams having become rotten and unsafe were thrown down the pot in July, 1893. Beyond the stones the platform, smooth and very slippery, gives out over a circular opening of the same character, and, as it slightly overhangs, this bit is not easy. Immediately overhead the spray from the waters of Long Churn kept up a continual though not heavy shower.  W. Parsons succeeded in climbing down without aid from the life-line; but the others relying on its support, and keeping as much as possible at right angles to the-steep face, were let down. Some amusing incidents occurred at this point; but with care and time every man of the ten – W. Parsons, W. C. Slingsby, C. Hastings, H. A Jeffery, F. S. Clay, H. Buckley, A. W. Bairstow, A. E. Horn, G. T. Lowe, and S. W. Cuttriss – reached the bottom of this pitch. The floor, thirty feet below, is formed of large loose blocks, and overhead the roof runs up into a sharp angle, seventy feet above. A stream, the combined waters of the two falls, rushes along the channel, which is now entirely underground. The black limestone through which we were here progressing was more slippery than the superincumbent white, and made our surroundings look very gloomy. Two more pieces of the old beams were passed, and high above, about midway along the passage, a long wooden rail was jammed, showing the height to which the torrent rises when in flood.

At last, after two low pitches and a continuous incline, we came to a beautifully rounded dip of about nine feet, terminating in a shallow pool. It proved a splendid sitzbath; then the final chamber was reached immediately beyond. The lip overlooked a black sheet of water, its surface broken by stones, and luckily for us of no great depth. The traverse down to the west side along a black wall brought us to the rough stone covered floor of a hall about eighty feet high, resonant with the roar of falling water. On our right looking north was a large waterfall some sixty feet high. It fell clear for about forty feet and then striking a ledge, broke into spray and completed the leap. The hall measured sixty feet long and thirty feet broad. The west side overhangs considerably. At the northern end, in a quiet pool close to the rock face, the water flows away into the unknown.

The surface water had been coloured with fluorescein, and down in the great hall, deep in the bosom of mother earth, this silent pool was tinged a beautiful greenish blue colour. The subterranean waterfall evidently descended from the passage explored on the previous day. But somewhere, between where we now stood and the abyss examined by the flare lamps, must be either a vast chamber or a series of cavities. In the south-west corner of the waterfall chamber, level with the floor, I noticed an opening leading back in the direction of the passage we had just traversed.

Two parties of five, each accompanied by Parsons, reached the final pool, and then the way to the surface was slowly won, as each stage had to be carefully retraced and all the tackle brought up. Tired and wet, but cheered by success, we at last reappeared at the mouth of Diccan pot – the first two men about five o’clock, when it was almost dusk.

Considering the size of the party, we were to be congratulated on our day’s work. To me it seemed one of the most successful expeditions the Club has ever done. The variety and beauty of Alum Pot are perfectly ideal. Almost every phase of underground exploration was represented, and the difficulties were not too great. The other giants of the district – Gaping Ghyll and Rowten Pot – we found more difficult and dangerous, the latter especially so.

Sketches were made and measurements taken during this and the last descent from which the preceding plan has been prepared. Later it is hoped a smaller party will undertake the task more scientifically. The actual depth of the final pool below the surface is usually given as three hundred feet, but we were inclined to think it a little under that figure.

During the last few years “The Movements of the Underground Waters of Craven” have engaged the attention of a committee of geologists, who are carrying on their investigations in conjunction with a committee of the Yorkshire Geological and Polytechnic Society, under the auspices of the British Association, and it is to

Mr. A. R. Dwerryhouse, M. Sc., F.G.S. (Secretary to the Society’s committee), that I am indebted for the following interesting particulars:–

“Special attention has been given to Ingleborough and its neighbour Simon’s Fell, a detached massif peculiarly suitable to the purpose. The summit of the group is Millstone Grit, then follow Yoredale Shales and sandstones, the whole resting on a plateau of Carboniferous Limestone.  Many streams rise in the upper slopes of the hills and flow over the Yoredales; but without exception their waters are swallowed directly they pass on to the Carboniferous Limestone, to reappear as springs in the valleys which trench the plateau.

“On June 21, 1901, Alum Pot was the scene of operations. The joints in the neighbourhood of Alum Pot are more complicated than in the parts of the district previously investigated, there being three sets of joints, all more or less irregular in places. Close to Alum Pot there are two sets running S. 5° W. and N. 80° E. respectively. Thirty yards higher up Alum Pot Beck they run due N. and S. and N. 80° E. the north and south joints being the stronger and more continuous. On the Clints 100 yards above the Pot there are three sets of joints, as follows, viz. :–

Master	.        .	N. 10° E.
		{N. 35° E.
Secondary	.        .	{N. 85° E.

“One pound of fluorescein was put into the stream flowing into Alum Pot on Friday, June 21st, at 7-0 p.m. There was not much water flowing at the time, and a few days afterwards several important springs in the neighbourhood ran dry, including that at Turn Dub, on the opposite bank of the Ribble, which is the reported outlet of the Alum Pot Stream. The springs commenced to flow again a few days later; but although they were carefully watched, as was also the river itself, no trace of colour was seen. It was therefore concluded that either the fluorescein had passed into one of the other river basins or had become so diluted as to be invisible.

“This experiment having proved inconclusive, a further one was commenced on Thursday, September 5th, when three-quarters of a pound of fluorescein was put into the water flowing down Long Churn, near Alum Pot, at 4-0 p.m., and a further quantity of three-quarters of a pound was introduced at 5-30 p.m. on the same day. It was afterwards learned that it issued from Turn Dub, on the opposite side of the river Ribble, and close to the bank of that stream, on September 17th. The water therefore took twelve days to accomplish a. journey of a mile and a half.

“The extreme slowness of the flow is partly to be accounted for by the dry weather which then prevailed; but when it is taken into consideration that the water of Long Churn plunges down a very steep fall into Alum Pot, the total depth of which is some 300 feet, the gradient of the remainder of the stream is considerably reduced. Mr. Wilcock, of Selside, informed me that the fluorescein mentioned above had been seen in Footnaw’s Hole, which is nearly a mile from Alum Pot, prior to its appearance at Turn Dub.

“In dry weather Footnaw’s Hole appears as a wide cleft in the limestone, with sloping banks of silt and sand round two sides and precipitous limestone rocks on the other two. When the streams are in flood after heavy rain or during the melting of snow the water in Footnaw’s Hole rises to the lip and flows over down Footnaw’s Beck into the Ribble.

“Turn Dub is very rarely dry, while it is only in exceptionally wet weather that water flows from Footnaw’s Hole. Thus it would appear that Footnaw’s Hole is a flood outlet, and only comes into operation when the underground passage leading to Turn Dub is full and, therefore, unable to take the excess of water. As the lip of Footnaw’s Hole is just below the 825 foot contour, and Turn Dub just below that of 800 feet, there cannot be a fall of more than 25 feet from the former to the latter.

“Further, since in ordinary weather when the stream is issuing from Turn Dub only, the water in Footnaw’s Hole stands some 20 feet below the ground level, it will be seen that there must be a siphon-like passage below the river; and since this passage must be constantly filled with water up to the level of the overflow of Turn Dub, it will account for the very slow passage of the fluorescein over at least this part of the journey.

“Since the water passes beneath the river Ribble it follows that .there must be some impervious cover, because if this were not the case the water of the underground stream would find an escape at the lowest point, namely in the bed of the river, and would not as is the actual case, pass under that stream and rise some 10 or 12 feet above it on the opposite bank.

“With a view to ascertaining the nature of this impervious cover and its thickness it was determined to carry out a series of boring operations in the alluvial flat between Turn Dub and the river.

“ln the first place Turn Dub was sounded and found to be only about 18 feet in depth. Now Turn Dub is a circular pond of still water, and although a large stream of water flows out there is no disturbance of the surface, no welling up of the water apparent. This would lead one to suppose that the pool was much deeper than is actually the case. So far as could be ascertained by drawing the sounding-iron across the bottom of the pool, this consists of large boulders. This led to the suspicion that the cover consisted of boulder clay, and that the bottom of Turn Dub consisted of boulders, the clayey matrix having been removed by the action of the flowing water.

“The boring operations were undertaken with a small set of hand boring-rods provided with an auger bit. With this apparatus it was possible to prove that the bluish alluvial clay was underlain by a material consisting of a somewhat sandy brown clay with many large stones, and in every way similar to the boulder clay of the neighbourhood, which in some places can be seen close to the river bank. The presence of the numerous boulders prevented the boring operations being carried more than a matter of one or two inches into the boulder clay, so that it was impossible to obtain any definite evidence regarding the thickness of the bed. Further, although boulder clay was proved to underlie the alluvium on both banks of the Ribble it was impossible to obtain evidence of its existence in the river bed, as this consists of coarse shingle which could not be penetrated by the hand-boring apparatus.

“In order to clear up this matter satisfactorily it will be necessary to engage the services of a professional well-sinker and to have one or two bore-holes put down by mechanical means.

“It was laid down in the two previous reports of this committee that as a general rule the flow of underground water in limestone rocks follows the direction of the master joints, and this view has been strikingly confirmed by several experiments which have been carried out during the current year. (1902). It may be confidently said that there is a general parallelism between joints and passages, but this is by no means as close as was at first expected.

“To account for the want of parallelism between joints and passages it is necessary to study the evolution of one of these underground chambers. The joints in the limestone undoubtedly give the initial direction to the underground stream; but as soon as a channel is formed sufficiently large to allow of a free flow of water, as opposed to mere soakage, a number of other forces come into play which tend to modify the direction so as to cause it to diverge somewhat from its original one of strict parallelism to the joints. For example, the dip of the rocks causes the erosion of the channel to be more severe on one side than the other – namely, on the low or  ?down dip’  side – and where there are cross-joints the dip may tend to produce a lateral escape along one of these so as to give rise to a zigzag course.

“Up to a certain point the erosion in these underground river channels is entirely by solution, but so soon as the external opening becomes sufficiently large to admit sand, gravel, and boulders, excavation by means of attrition comes into play. At this point in the history of a subterranean river zigzags are changed into sharp windings, which in their turn impart a swing to the waters in the straight parts, thus causing a series of windings to be set up in a manner similar to that which goes on in surface streams.

“As the external opening which gives access to the water increases in size, so does the amount of water flowing through the passage increase. An increase of volume means an increase of speed and a lessened tendency to winding; at the same time the passage must be widened so as to accommodate the increased volume of the stream. The tendency at this stage is, then, to widen and straighten out the passages, and many are the deserted ‘ox-bows,’ both large and small, which may be seen in the passages. Some of these are small and situated at a considerable height above the floor of the main passage, while others of more recent formation are approximately at the same level as the water-bearing passage, a few of them still being occupied by a portion of the stream in times of flood. The condition of approximate stability is reached when the opening becomes sufficiently large to swallow the whole of the surface stream.

“The probable manner in which the underground channels are opened out by erosion, and later, as they increase in size, are scooped by the attrition of running water bearing sand and stones, is consistent with the appearance of the numerous subterranean passages I have explored; but a satisfactory explanation of an earlier condition of the limestone, when the minute cracks and fissures were in the process of being enlarged, is still wanting. There are irregular series of vast chambers, the varying altitude of whose roofs is most perplexing as their walls show no signs of erosion. Many of the nearly vertical pot-holes certainly show the results of water action at the point of  influx of the stream, which as a rule empties its waters into their recesses; but many features of the shafts and the spacious halls in the passages below ground do not appear to be due to water action altogether. Neither does the falling in of a chamber roof at successive stages in its formation always account for its great width or length. The roofs in many instances do not even suggest that blocks have been detached from them. The quantity of water which flows through some caves also is too small to be responsible for the destruction of so much fallen rock. Where the floor is of sand however – as in Gaping Ghyll cavern -such blocks may lie hidden beneath.

To our early ancestors these pot-holes were dark, mysterious, and forbidding, indeed, veritable mouths of hell, and recent writers do not hesitate to use the most gruesome phrases to describe their hidden terrors. Mountaineering reversed is much more difficult than climbing in the open air. The dim light of spluttering candles or the intermittent blaze of a flare lamp is a poor substitute for sunlight. The feeling of being shut in quickly wears off, and the novice soon acquires the knack of groping in the semi-darkness. It may seem an exaggeration to say that cave-exploration is fascinating, but it is true nevertheless. It often entails hard and nearly always dirty work. There is danger which, with the exercise of caution may be safely encountered, and, more than all, under these adverse conditions one gets to know a man better in a day than in many years of ordinary social intercourse. Friendships are formed which will never be forgotten. The excitement is infectious, and it is delightful to see the boys of forty years and more displaying the spirit and fun of early youth.

It is strange that no better name than Pot has been found for the numerous and curious openings reaching in many instances right through the limestone, which must be fairly honeycombed. Occasionally the surface rock has fallen in, and great depressions have been formed. Changes are still going on, slowly, but yet surely, and in some instances these can be noted. Here at hand a sport is available, second to none for excitement and the awe of the unseen. It was until recent years practically unknown, and although much has been done, much remains to be accomplished. Descriptions of Yorkshire caves and pot-holes which appear in ordinary guide-books are frequently misleading, being for the most part the result of hearsay and conjecture. Their writers have not had personal experience, and erroneous information they have received has been accorded the permanent confirmation of print.

Some day, perchance, the discovery of a second Victoria or Kirkdale cave will reward our men, and we shall feel that our labours have not been in vain. Meanwhile, on the quiet, bare sides of our almost treeless fells, these holes and caverns lie challenging the ardent explorer to further efforts, and the challenge is not in vain.