(This is an extract from 'Cave Hunting' by W. Boyd Dawkins, published by Macmillan in 1874. The description is somewhat more atmospheric than the description of Alum Pot that appears in 'Northern Caves'!)
The subterranean passages grouped around Helln Pot, a tremendous chasm near Selside, on the east of Simon's Fell in Ribblesdale, illustrate in a remarkable degree the mode in which the water is at present wearing away the rock. Those which have been explored constitute the Long Churn Cavern, which is comparatively easy of access through a hole known as Diccan Pot. On descending into it, the visitor finds himself in the bed of a stream that now roars in a waterfall, now gurgles over the large fallen blocks from the roof, and that here and there has worn for itself deep pools by the mechanical friction of the sand and pebbles brought down by the current. If it be followed down after passing over a waterfall, the light of day is seen streaming upwards between the feet from the point where the water leaps into the great chasm of Helln Pot. Above the entrance there is a complicated network of passages, some dry, and some containing streams which have not yet been fully explored.
The two actions by which caves are hewn out of the calcareous rock are seen here in operation side by side. Below the level of the stream the rock is seen to be smoothed and polished by the mechanical action of the materials swept down by the current. Above the water-level the sides of the cave are honeycombed and eaten into the most fantastic and complex shapes, the resultant surface bearing small points and keen knife-edges of stone, that stand out in relief and mark the less soluble portions of the rock. This is due to the chemical effect of the carbonic acid in the water percolating through the strata.
The Helln Pot, into which the stream flowing through the Long Churn Cave falls, is a fissure a hundred feet long by thirty feet wide, that engulfs the waters of a little stream on the surface, which are dissipated in spray long before they reach the bottom. From the top you look down on a series of ledges, green with ferns and mosses, and, about a hundred feet from the surface, an enormous fragment of rock forms a natural bridge across the chasm from one ledge to another. A little above this is the debouchement of the stream flowing through the Long Churn Cave, through which Mr Birkbeck and Mr Metcalfe made the first perilous descent in 1847. The party, consisting of ten persons, ventured into this awful chasm with no other apparatus than ropes, planks, a turn-tree, and a fire-escape belt. On emerging from the Long Churn Cave they stood on a ledge of rock about twelve feet wide, and which gave them free access to the "bridge". This was a rock ten feet long, which rested obliquely on the ledges. Having crossed over this, they crept behind the waterfall which descended from the top, and fixed their pulley, five being let down while the rest of the party remained behind to hoist them up again. In this way they reached the bottom of the pot, which before had never been trod by the foot of man. Thence they followed the stream downwards as far as the first great waterfall, down which Mr Metcalfe was venturesome enough to let himself with a rope, and to push onwards until daylight failed. He was within a very little of arriving at the end of the cave into which the stream flows, but was obliged to turn back to the daylight without having accomplished his purpose. The whole party eventually, after considerable danger and trouble, returned safely from this most bold adventure.
A second descent was made in 1848 from the surface, and a third in the spring of 1870, in both of which Mr Birkbeck took the lead. The apparatus employed consisted of a windlass, supported on two baulks of timber, and a bucket, covered with a shield, sufficiently large to hold two people, and two guiding ropes to prevent the revolution of the bucket in mid air. There was also a party of navvies to look after the mechanical contrivances, and two ladders about eight feet long to provide for contingencies at the bottom. Thirteen of us went down, including three ladies. As we descended, the fissure gradually narrowed, until at the bottom it was not more than ten feet wide. The actual vertical descent was a hundred and ninety-eight feet. After running the gauntlet of the waterfall we landed in the bed of the stream, which hurried downwards over large boulders of limestone and lost itself in the darkness of a large cave, about seventy feet high. We traced it downwards, through pools and rapids to the first waterfall, of about twenty feet. This obstacle prevented most of the party going further, for the ladders were too short to reach to the bottom. By lashing them together, however, and letting them down, we were able to reach the first round with the aid of a rope, and to cross over the deep pool at the bottom. Thence we went on downwards through smaller waterfalls and rapids, until we arrived at a descent into a chamber, where the roar of water was deafening. Down to this point the daylight glimmered feebly, but here our torches made but little impression on the darkness. One of the party volunteered to go dowm with a rope, and was suddenly immersed in a deep pool; the rest, profiting by his misadventure, managed to cling on to small points of rock, and eventually to reach the floor of the chamber. We stood at last on the lowest accessible point of the cave, about 300 feet from the surface. It was indeed one of the most remarkable sights that could possibly be imagined. Besides the waterfall down which we came, a powerful stream poured out of a cave too high up for the torches to penetrate the darkness, and fell into a deep pool in the middle of the floor, causing such a powerful current of air that all our torches were blown out except one. The two streams eventually united and disappeared in a small black circling pool, which completely barred further ingress.
The floor of the pot and the cave was strewn with masses of limestone rounded by the action of the streams; and the water-channels were smoothed and grooved and polished, in a most extraordinary way, by the silt and stones carried along by the current. Some of the layers of limestone were jet black, and others were of a light fawn-colour, and as the strata were nearly horizontal, the alternation of colours gave a peculiarly striking effect to the walls. Beneath each waterfall was a pool more or less deep, and here and there in the bed of the stream were holes, drilled in the rock by stones whirled round by the force of the water. High up, out of the present reach of the water, were old channels, which had evidently been watercourses before the pot and cave had been cut down to their present level. In the sides of the pot there are two vertical grooves reaching very nearly from the top to the bottom, which are unmistakeably the work of ancient waterfalls. There was no stalactite, but everywhere the water was wearing away the rock and enlarging the cave. We found our way back without any difficulty, a small passage on the right-hand side enabling us to avoid the very unpleasant task of scrambling up two of the waterfalls. We arrived finally at the top, after about five hours' work in the cave, wet to the skin.
We had very little trouble in making this descent, because of the completeness of Mr Birkbeck's preparations; but we could fully realise what a dangerous feat the first explorers performed when they ventured into an unknown chasm, comparatively unprepared. The very name "Helln Pot," = Ællan Pot, or Mouth of Hell, testifies to the awe with which the Angles looked down into its recesses. (On the Ordnance Maps it is wrongly printed Alum Pot).
Such is the interior of one of those great natural laboratories in which the water is wearing away the solid rock, either hollowing it into caves or cutting it into ravines. At the bottom of Helln Pot it was impossible not to realise, that the enormous chasm had been formed by the same action as that by which it was being deepened before our eyes. It was merely a portion of the vast cave into which it led, which had been deprived of its roof, and opened out to the light of heaven. The bridge was but a fragment of the roof which happened to fall upon the two ledges. The rounded masses of rock at the bottom are fragments that have fallen probably within comparatively modern times. The absence of stalactites and of stalagmites proves that the destructive action is rapidly going on.
The water-course at the bottom contained pebbles and boulders of limestone, and gritstone rounded by friction against one another and the rocky floor. The gritstone has probably been derived from the wreck of the boulder clay on the surface above Helln Pot, and ultimately torn from the millstone grit of the higher hills in the district.