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THE CAVE DISTRICT OF THE MENDIPS

"A land of caves, whose palaces of fantastic beauty still adorn the mysterious underworld where murmuring rivers first see the light." In these words an imaginative writer describes Somerset, which shares with Derbyshire and Yorkshire the title of a land of caverns. Across it the range of the Mendips, a region of Old Red Sandstone and Carboniferous Limestone, 1000 feet above tide-level, stretches in a huge, flat-topped rampart for nearly 30 miles, from the town of Frome to the sea. No piece of country in the kingdom offers so much to explore. An abundant harvest is there waiting to be reaped; for on every side are obvious indications of half-buried gateways to the dark and secret pathways to the netherworld, and everywhere upon the surface of the Mendip tableland lie the open pits and hollows which the local speech calls "swallets," that is to say, swallow holes, some of them dry, some actively engulfing streams, but all testifying to untold ages of water action.

This Limestone district lies far from the busy hives of industry, remote and secluded in the very heart of lovely Somerset. Only on the darkest of nights, with the clouds low in the sky, can the glare of the lights of Bristol be seen reflected far to the northward. One main line of railway, the Great Western from Bristol to Exeter, passes near it, and even that does not intrude beyond the margin of this Caveland. The rendezvous for the cave explorers of the district is usually the quiet little city of Wells, lying calm and secluded under the southern slopes of Mendip, in close proximity to all the principal caverns. A mile to the south-east rises the bold and picturesque Dulcote Hill, a fragment of the most southerly anticline of Mountain Limestone in the kingdom. From this point, rolling northward in a great fivefold anticline, Old Red Sandstone, Lower Limestone Shales, and Mountain Limestone form the great mass of the worn-down stump of the once mighty Mendip range. The extent of the denudation which has taken place indicates that this range was originally at least 5000 feet high, yet now in but a few places is the height of 1000 feet attained, and this is reached only by the Old Red Sandstone ridges laid bare in the prolonged course of that denudation. The first of these high ridges rises boldly to the north of Wells, and a steep climb of 900 feet in two and a half miles brings us to the summit of Pen Hill, or Rookham, from which a grand southward view is to be obtained. Immediately below, the three cathedral towers pierce the blue mist hanging over the little city we have just left. Beyond, the peat moors of the Brue and the Axe stretch away to the Isle of Avalon, sacred as the birthplace of our Christian faith in England. Here below us is that

"Island valley of Avilion,

Where falls not hail, or rain, or any snow,

Nor ever wind blows loudly; but it lies

Deep meadow'd, happy, fair with orchard lawns,

And bowery hollows crowned with summer seas."

Here, where Arthur's bones are said to have been found, and where traditions associated with him abound, his memory is kept green in the names of many well-known spots; and yonder rises Cadbury Camp, looked upon by many as the Camelot of romance. On the low ridge which intervenes between the valleys of the Axe and the Brue lies Wedmore, where King Alfred gained in the Peace of Wedmore such temporary respite from his foes as allowed him to gather strength for the great operations that resulted at last in the conquest and unity of the whole kingdom. Yonder, too, are the marshes of the Parrett and the Tone, around which cluster tales familiar to every schoolchild. In the marshes between the Mendips and Glastonbury, exploration has unearthed a most interesting example of a swamp or lake village, with great store of antiquarian material, throwing a flood of light upon a period of which little was known. Beyond lies Sedgemoor, where in 1685 took place the last battle ever fought on English soil; and throughout this neighbourhood the infamous Jeffreys worked his will in the judicial slaughter of countless Somerset men.

In the far distance the sunshine glints on the waters of the Bristol Channel, where, 60 miles away, the bold promontory of the Foreland rises sheer from the sea; to the south, upon the farthest limits of our vision, Pilsdon and Lewsdon mark the descent of our southern counties to the English Channel; whilst, on a clear day, between them is seen the summit of Golden Cap, the base of which is washed by our southern sea. Surely here is as fair a scene as eye could wish to see.

Only a pleasant walk away, the great chasms of Ebbor and Cheddar have rent the rocks asunder, forming two of the loveliest ravines in the kingdom. Northward across the intervening syncline of Mountain Limestone, pitted with swallets marking the entrances to many an unknown subterranean labyrinth, are seen the Old Red Sandstone summits of North Hill, crowned with its seventeen Neolithic barrows, and of Blackdown beyond, from whose bare top is seen the broad estuary of the Severn spreading out across the view, giving a glimpse of the coast of South Wales in the far distance, its busy factories showing their pencil-like chimneys against the dark hills behind. In the Channel the little islands of Steepholm and Flatholm mark the line of the original continuation of the great Mendip range into South Wales. The limestone shores of the former rise sheer from the sea, forming an impregnable fortress. Here, far below the level of the salt water around, a supply of pure water is obtained from the Limestone, brought, doubtless, from the Limestone area of Mendip by way of some hidden fissure.

Hard by, at Clevedon, is the grave of that great friend of Tennyson, who sat here and listened to

"The moaning of the homeless sea,

The sound of streams that, swift or slow,

Draw down æonian hills, and sow

The dust of continents to be."

Very truly and accurately his words describe the action that is going on, by which the swallet streams are undermining and honeycombing these hills and bearing their component rocks away to the sea.

Standing on Pen Hill and looking northward, a great east and west depression is seen forming a broad low valley in the tableland of Mendip. Into this valley numerous springs and a liberal rainfall are for ever pouring their waters. Yet nowhere is there a surface channel which can carry this water away; and nowhere, save in the small hollows of the Old Red Sandstone and Shales, does water accumulate. The reason is not far to seek. The Carboniferous Limestone, evenly stratified everywhere, has been split by vertical joints into a series of gigantic cubes. Between them, the surface waters, laden with carbonic acid obtained from the atmosphere and from vegetation, have for ages made their way, enlarging them by both chemical and mechanical action, till they have become fissures capable of giving passage to an enormous quantity of water. So from one joint to another, from one bedding plane to another, the water percolates downwards until it meets with some impermeable rock beneath, or until it finds an outlet at the level of the Secondary rocks forming the valley below. Such impermeable beds are found in the Lower Limestone Shales, and the resulting outlets are well known in the great risings of St. Andrew's Well in the gardens of the Bishop's Palace at Wells, in the source of the Axe at Wookey Hole, in the Cheddar Water and other large springs, of all of which more hereafter.

MAP OF THE MENDIP DISTRICT OF SOMERSET, SHOWING SWALLETS, CAVES, AND OUTLETS.

(Click on map to see a larger version. Not available on all devices.)

Reference to the sketch map of the district will show that the majority of the more important swallets lie along the line of the great depression referred to. These comprise by no means all the swallets of Mendip, yet they are the chief ones. It is obvious that the whole of the mass of material represented by this great depression has been removed in suspension by way of these swallets; and one is compelled to ask, How long has this work been going on? What time is represented by so vast a work? On the threshold of the inquiry we are met by such an amount of evidence bearing upon it that the subject must be dealt with separately. For, upon the upturned edges of the Carboniferous Limestone rocks, which can have been brought down to their present plane of denudation only by long-continued water action, have been deposited, and still remain in situ, great masses of the basement beds of the Secondary rocks, lying in such a manner as to convince us that swallet action had prepared the denuded surfaces upon which they lie. And upon this hinges the whole question of the antiquity of the caverns of Mendip. But whilst the age of our caverns is a debatable matter, no one can question the accuracy of the theory of ravine formation from the collapse of cavern roofs, as evidenced by the instances supplied by Mendip.

Through crevices and cracks, here, there, and everywhere, the percolating waters find their way. Now some crevice is enlarged into a passage; now some weak point in the passage becomes a chamber; and on the water rushes, steadily joining forces and accumulating, until on the level of the lower land it finds an outlet, and rushes forth a considerable stream. In its headlong course the water again and again leaps down some great series of potholes, as down some giant stairway, forming many fine cascades, whose deafening roar goes on for ever where there is no ear to hear and where no footstep ever treads the rocky ways. Along the course of the larger streams huge chambers occur; for the ever-eddying water, bearing sand along in its course, eats out the sides of its channel, or, revolving stones in its bed, carves out the pothole by friction. Or some pendent mass of rock has its support undermined and comes crashing into the streamway, only to be broken up and carried away by the ceaseless energy of the stream, so ever enlarging the chambers upwards towards the light of day. But whilst this action is going on underground, a more potent factor is at work where the subterranean stream first sees the light. Here very soon the action of the water alone gives rise to a little cliff overhead. Now rain and frost, wind and tempest, loosen, bit by bit, the fragments of rock forming the face of the cliff, which fall away into the river, to be broken up and carried away. Little by little the face of the cliff recedes, along the line of the subterranean river, until the first underground chamber is reached. The undermined archway of rock is less able to withstand the agents of denudation, and the cliff front recedes apace. Such is the present stage at Wookey Hole, the chamber whence the river Axe issues being still in process of destruction. Thus the work goes on slowly, yet none the less surely, until along the whole course of the subterranean river the roof of the cavern is destroyed, perhaps effectually hiding the stream under huge blocks of Limestone, such as those of Ebbor Gorge, near Wells, or until the water finds another course for itself, as at Cheddar, to begin the whole story over again. Every stage is abundantly illustrated by our Mendip swallets and caves. The large swallets of Eastwater, three and a half miles from Wells, of Swildon's or Swithin's Hole, a half-mile nearer Priddy, and the more recent swallet of Stoke Lane, half-way between Wells and Frome, are excellent examples of streams engulfed on the summit of Mendip. The whole of the country surrounding the two first-named caverns is dotted with innumerable small pits and hollows. The great swallet of Hillgrove, three miles north of Wells, in the exploration of which we are at present engaged, in an endeavour to penetrate the labyrinth of ways to which it will undoubtedly afford access, is a fine example of an intermittent swallet. Here three ways, carved deeply through the stream-borne sands and clays of some uncertain epoch of geological history, converge in a deep glen, beautiful with its tropical wealth of ferns. In the bottom of the glen huge spurs of Limestone stand up boldly, dipping towards the Old Red Sandstone exposed to the south, and pointing to a great fault, along the line of which the Limestone water is bound to accumulate in a huge triangular reservoir, the outflow from which may account for the summer flow of the Axe when the majority of the swallets are dry. In winter the converging torrents here find ingress into the Limestone, but, though pits and hollows abound on every hand, no foot of man has ever yet trod the hidden ways beneath. At a depth of 10 feet we have reached the first open channel, only to have it blocked subsequently by a fall of the treacherous gravel through which we have been working.

Vast dry swallets are represented by a great depression which we call the Bishop's Lot Swallet, on the road from Wells to Priddy. Here a huge hollow in the ground, perfectly circular and 300 yards round, shows us the largest swallet in Mendip. Though the surrounding land slopes gently to the edge of the great pit, which is 60 feet in depth, there is but the smallest trace of water penetrating it. It is ages since the drainage of the surrounding land gravitated towards it, for it lies at a considerable height above the level of most of the other swallets in the neighbourhood. A mile and a half to the west, a similar pit occurs called Sand Pit Hole. Here too water has ceased to flow, and it remains, with precipitous sides, a problem for us to investigate in the near future.

To enter either of the active swallets of Eastwater or Swildon's Hole, and to follow it to its greatest depth, is to gain an insight into the action of subterranean streams such as no other method can give. The former is well illustrated by the annexed section, in which its profound depth and its labyrinth of passages may readily be understood. The difficulties and disappointments which we encountered when I conducted the operations which at last resulted in our effecting an entrance into this cavern, the existence of which was not even suspected previously, need not here be recapitulated. Altogether, what with volunteers and labourers, nearly a dozen of us were occupied ten days in the determined effort which we made, and which at last was crowned with success. From the point of view of the subsequent explorer the reader is referred to the ensuing chapter upon Eastwater Cavern, which will convey some idea of what the first explorers must undergo in any such place when to the ordinary difficulties of such an exploration is added the great uncertainty felt at every step taken, and when every boulder upon which our weight is to rest must first be carefully examined. The difficulty of our work at Eastwater is practically what must be experienced in any new work undertaken in the Mendip region, and there is much waiting to be done. If there is one thing more than another to be learned from Eastwater Cavern, it is the great importance of chokes in determining the lines of subterranean drainage. Here they are seen in every stage of formation and destruction, and the channels which have been carved by the arrested water may be readily recognised.

There is a fascination in exploration work such as that at Eastwater, where corridors, hitherto untrodden by the foot of man, open up all around as you make your way ever downwards into the heart of the hills; and even now there are many accessible passages into which as yet no one has penetrated. Reference to the section annexed will show an upper way, which terminates abruptly in a choke of stones and gravel, holding up a little water, whilst allowing a considerable quantity to pass. It is a remarkable fact that in all the labyrinths of galleries which we have explored in the profound depths of this cavern we have not yet alighted upon any portion which gives access to the continuation of this channel. There, rendered inaccessible by the barrier of débris, is, without doubt, a cavern as extensive as that which we have proved to exist in the sister watercourse hard by; and these two channels, starting from practically the same point, must diverge widely, and certainly do not unite again before the depth of 500 feet is attained.

Farther eastward in Mendip, too, are similar swallet caverns. Not far to the north-west of Stoke Lane is an interesting cavern locally known as Cox's Hole. It is situated in the Limestone forming the southern edge of the great basin in which lies the Radstock Coalfield. Owing to the existence of this coalfield, there are no deep caves accessible in this part of Mendip. Yet a good deal of water must be absorbed through the innumerable fissures into the depths of the Carboniferous Limestone underlying the coalfield, and it is by no means unlikely that this water, heated to a high point by the subterranean temperature, gives rise to the hot springs at Bath. Cox's Hole was at a remote period, when the form of the hill was very different from that presented now, an active water-channel, evidently draining towards St. Dunstan's Well. It has two distinct entrances, one, the more westerly, being a cavity of considerable size. For about 100 feet the cavern consists of a roomy gallery running more or less horizontally. Then it pinches in, until the height is less than a foot, and only those can get along who are able to compress themselves into small compass. In a few feet, however, it widens out into a good-sized passage, with fine stalactites here and there, especially at a point on the northern side where an aven opens into a chamber more than 30 feet high. Now roomy and now contracted, the passage leads on until, at a distance of 100 yards from the entrance, it becomes so small that there is considerable difficulty in proceeding. Beyond this point the cavern becomes a simple water-tunnel, of a type common in Yorkshire. At 130 yards there is a sharp descent, the floor is littered with boulders, and 20 yards farther the passage is choked with silt. A very small passage, which had water in it when I was there, is said to be passable at times, though I am inclined to doubt this. An almost vertical ascent amongst treacherous boulders, however, seems an indication of a possible route onwards, which may, I trust, with care be yet explored. The last 50 yards of the cave run to the south-east—that is, away from the direction of St. Dunstan's Well—a beautiful spring rising from the Carboniferous Limestone hard by; yet I feel sure that it must of necessity be a part of the same waterway. Either it was an inlet which received the waters of some vanished Old Red Sandstone spring, or it was a former outlet for the waters of that well. I am inclined to favour the former theory. As to the present source of the waters of St. Dunstan's Well there can be no doubt whatever. In the valley below Stoke Lane, and three-quarters of a mile distant from the well and from Cox's Hole, there is a most interesting swallet, of comparatively recent age. It is obviously certain that, not so long ago, the stream which courses down the valley flowed unchecked down its whole length, and so reached the larger stream below. Slightly retarded, in all probability, by some flood-borne silt, the water found a little joint in the western bank of the valley, and by slow degrees so enlarged it that it at last became capable of swallowing the whole. Even now a few hours' work would divert the water and cause it to resume its former course. Upstream is a mill, the owner of which has courteously given every facility for testing and for exploration. It was found that the effect of damming the mill stream entirely was to reduce the flow at St. Dunstan's Well enormously, and to render the entrance of the swallet passable. Mr. Marshall of Stratton-on-the-Fosse with his party made a successful descent, and travelled a considerable distance, mainly parallel with the valley without and to a great extent horizontally, through water-tunnels of small size. As no measurements were taken one cannot say yet how far it is passable, but he says that they did not get to the limits of possible exploration, as the time which they spent there was getting dangerously near the hour up to which it is possible to dam the water, and they most wisely beat a hasty retreat. The first opportunity will be taken by us to make use of a spell of fine weather to carry this exploration to a successful issue. Not far distant, too, is another swallet, from which the water has been diverted to be used for water-supply. This is in the vicinity of a ruined hunting lodge, and is said to lead in the same direction as the Stoke Lane Swallet. The whole of this district is likely to be very interesting, there being a series of remarkable rifts or fissures in the Dolomitic Conglomerate which deserve attention. One of these, called Fairy Slats, has been known for many years, and is indeed shown on the Ordnance map; and the fact that such fissures abound has been forcibly brought home by a disaster to a new reservoir, only recently completed by the authorities of Downside Monastery, to supply the neighbouring villages. Here a finely designed basin, having been constructed over one of these fissures, had its massive concrete bottom burst out as if it were an egg-shell the moment the water filled it, and in a single hour the whole fabric was absolutely ruined. Some measure of the extent of the concealed fissures may be gathered from the fact that 500,000 gallons of water were absolutely swallowed up without a drop coming to light in the neighbouring valley. An early visitor to the adjoining field reported that air was being ejected through the grass all around him, much to his alarm, as he was quite unaware of what had occurred. It will be a most interesting subject for inquiry, as to how far such fissures as these are the results of water action or otherwise, and it is most desirable to descend one of them at the first opportunity in search of evidence. At present I am inclined to attribute their presence to movements in the Secondary rocks, due to the intersection of the district by valleys. The Conglomerate mass has parted along the lines of the principal joints, and the rifts thus formed have become lines of drainage. This theory, in view of possible future discoveries, may have to be modified.

Above Stoke Lane Swallet, and evidently connected with it in some remote way, is a cavity without a name, the exploration of which would probably be interesting, and would be most likely to yield remains of primitive Man. Mr. Marshall also reports the existence of a fissure of considerable size, where, after a very small entrance, a point is reached with a vertical descent of great depth. All these things indicate that there is a splendid field here for further work.

Indeed there are abundant evidences of this all over Mendip. One of the most interesting problems has had further light thrown upon it by work recently done by us at Wookey Hole. The Hyæna Den and the Badger Hole are testimony that a large amount of underground action has taken place upon the east side of the ravine, yet nothing has been known hitherto of any series of dry channels upon that side. Recently, however, we have succeeded in gaining access, by way of the smallest of fissures, into what will turn out most likely to be a portion of this very series. Here is to be seen a choked-up chamber of precisely the same type as the Hyæna Den, but far deeper in the wall of the ravine. Without doubt it contains prehistoric remains, yet its excavation will entail great labour. We have already reached a distance of 80 feet from the entrance, and only a partially choked passage bars the way.

High up in the ravine at Ebbor, too, there is a very promising field for further research. This is immediately beneath a cliff on the western side of the valley, where we have already done much preliminary work. There is also a very promising little cave, slightly north of Tower Rock in the same gorge and high up in its side. Here a narrow entrance gives access to a small chamber, on the floor of which is a deep deposit of cave earth, from which I have obtained Deer bones.

At Dulcote, again, there is a series of waterways and dry caves of great interest, which in themselves bear corroborative evidence of the great antiquity of the caverns of the district. From time to time the quarrymen have broken in upon these waterways, which have been lost in subsequent operations. Not many years ago a blast blew off the top of an almost vertical shaft, carved out in the Limestone by water action and descending to a great depth. The mass of rock blown off by the charge turned over and fell down the shaft, blocking it at 30 feet from the surface. It was possible to descend to this point and throw down stones, which fell for a considerable distance; but the block was never moved, and in the process of quarrying the hole became filled, and is now lost in the general level of the quarry. Hard by, also, a cavern of considerable extent was opened, and still remains. It contains nothing of peculiar interest, though when I was first lowered into it, from a hole 60 feet above its floor, it contained very pretty coral-like splash stalagmite; and also, in the mud floor, the tubular linings of calcite, formed from the drip from above. In this quarry, too, were found a considerable quantity of the bones of Bear, Deer, Bos, Horse, etc., and these are now in the Wells Museum, where they were deposited some years since by A. F. Somerville, Esq. There are numerous other minor caves in this locality. Farther up the same valley, above Croscombe, is a small cave known locally as Betsy Camel's Hole, and it appears to have been occupied by a woman bearing that name for some years. She was, of course, carried away by the devil, according to the same popular report. It may very well have been a rock shelter at some stage of its history. Mr. Somerville informs me, too, that in Dinder Wood there is a small cave which was almost certainly a rock shelter. This also has never been explored. In fact, the whole district may be described as an unexplored field, and there is abundant room for willing helpers. The landowners, for the most part, are exceedingly kind and ready to offer every facility for scientific research.

H. E. B.