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.