When we consider the question of the age of our caverns, we are met at the outset by a mass of evidence forcing upon us the certainty that they must be credited with a very high antiquity indeed. Here measurement by years and centuries fails, and the imagination must be called in to aid us to compute the epochs that have successively elapsed since the first cave, to take one example, began to be formed at Wookey Hole. These evidences are of three kinds: historical, palÆontological, and geological. In the first place, there has been obviously little change in the general configuration of our caverns since earliest historical times. The dens and caves of the earth have afforded a retreat to the persecuted of all generations, and a ready-made home when all else has failed. Here, too, with the rocky walls behind him and his protecting fires at the entrance, early man could defy the savage beasts that roamed the land in those far-off days.

At Wookey Hole it was only necessary to scratch the very surface of the accumulated dÉbris within the mouth of the great cave to turn up fragments of Romano-British pottery and a human jaw and rib-bones. These interesting relics are in the possession of myself and Mr. Troup. From the very nature of the place, it is obvious that the tendency has been to accumulate more and more dÉbris upon the mass of cave earth which contains these remains. Slightly deeper, yet still only in the loose earth of the cavern mouth, we found pottery of still earlier date, unwheeled and cruder. The fact is borne in upon us, that certainly for two thousand years this entrance has remained much as it is now. Perhaps a loose rock here and there has been dislodged from the overhanging cliff outside, and, crashing to the stream bed below, has there been broken up and carried away by the river. But no one can doubt that the general outline is the same now as then. And farther within the cavern an interesting sidelight is thrown on the slowness with which things change in the underworld. At the descent into the first great chamber a chalk inscription roughly made reads "E A 1769." That inscription has been there unchanged, to my knowledge, for the last twenty years, and I have no reason to doubt its authenticity. If a chalk mark remains unerased for a century and more, how long have those solid walls stood, and how long will they endure?

As I have gazed upon that inscription, the thought has come, that such a place as this would be an ideal site for national monuments. When our abbeys and cathedrals are crumbled away, these great subterranean halls will remain practically unchanged. And in the caves of Cheddar like evidences meet the eye. In the loose material in the Roman cave there, Roman and Romano-British remains have been found in abundance; and here again we are forced to the conclusion that no change has taken place since those remains were deposited.

But when we consider the evidences furnished by the remains of the extinct mammalia, mingled with those of primitive man, much more is it impressed upon the mind that we are dealing with relics of enormous antiquity. The great assemblage of bones of the extinct animals which occurs at Banwell Cave, and the numberless finds from the caves of Cheddar, are indications of this; but those of the HyÆna Den of Wookey Hole, and the conditions of their deposit there, afford us much more reliable testimony. Here are two principal cavities on the eastern side of the ravine, representing two of the five river levels which the stream of the Axe has hollowed for itself in the Dolomitic Conglomerate. These are branch or side chambers which have not been totally destroyed in the process of erosion that formed the ravine at the expense of the cavern. In the uppermost cavity, known as the Badger Hole (it was the haunt of badgers until a few years ago), no traces of the extinct mammalia are to be found, nor have I found definite traces of prehistoric man. At seven feet below the surface, however, there is a bed of river sand of precisely the same kind as that in the upper chambers of the great cavern. In the HyÆna Den below, on the other hand, so thoroughly and systematically explored by Professor Boyd Dawkins, was found one of the most perfect assemblages of the remains of extinct animals ever discovered. Many years after his labours were completed I searched there again, and was rewarded with a by no means poor collection of bones and teeth: Mammoth and Woolly Rhinoceros, Irish Elk and Reindeer, Red Deer, Bison, Cave Lion and Bear, HyÆna and Wolf, Wild Goat, Wild Horse, and Wild Boar have all been found. One of my earliest trophies was a fairly complete skull of a young Bear; and I have representatives of all the others. From a small hole in the side of the valley hard by, which I thought looked promising, we have obtained a large number of Rhinoceros teeth, together with those of several of the other kinds present in the Den. The examination of these cavities and their contents demonstrates the fact that they were the actual dens of some of these animals. The abundant marks of gnawing show that the HyÆnas made their home there. Over the vertical cliff many a worn-out beast was hunted to its death by the HyÆnas and Wolves, and its shattered carcass dragged to this hole.

ROMANO-BRITISH POTTERY, COINS, HUMAN REMAINS, ETC., WOOKEY HOLE CAVE.

Photo by H. E. Balch.

HYÆNA DEN AND BADGER HOLE, WOOKEY HOLE.

Photo by Bamforth, Holmfirth.

It is easy to wander back in imagination and bring the state of things that existed visibly before the mind's eye: to watch the unwieldy Mammoth or the great Rhinoceros rolling its huge bulk along; to see the pack of cowardly HyÆnas or Wolves hounding some worn-out Bison to its death, over the awful cliff close by their den, which purpose effected, they themselves rushed headlong down the steep slope hard by, to fight and wrangle over the shattered carcass of their prey; or to see the Lion lying in wait by the peaceful stream in the little valley for the noble Elk or timid Deer to come for its accustomed drink; and then to behold savage Man, with his weapons of flint or bone, when out on his hunting expeditions, arriving at this peaceful valley, and there for a while making his quarters in the Den, and lighting his fires at the entrance to scare the wild beasts from their lair.[1]

How long ago this state of things existed is a matter for geological calculation. Suffice it that the earliest historical records show us no wild beasts existing in the land except Bears and Wolves, along with the Red Deer which is with us to this day. Now there is no sign at Wookey Hole of the time when the Bear and Wolf alone remained and all else had become extinct from the land. There is no trace whatever in the HyÆna Den of the pottery which we find in the entrance of the great cave. Without a doubt, the latest deposits here are vastly older than the most ancient deposits there. The commingling of northern, temperate, and southern forms gives evidence of oscillations in temperature such as demand a vast time to have taken place. Yet the whole of these remains accumulated between the time when the entrance to the Den was left exposed by the gradual destruction and retreat of the cliff face up the valley, and the infilling and choking of the entrance by the accumulating gravel which eventually blocked it. It is only within the last few years that the gravel arch which was first formed, and then undermined in the search after bones, has collapsed, revealing the true configuration of the cavern. Here we must again postulate a great antiquity for our caverns, since these deposits exist in what is really an insignificant fragment of the great cavern, and are only an incidental part of the material which an exposed cavity is sure to receive. But when purely geological evidences are taken into account, the demand for time becomes still more imperative. The subterranean Axe occupies, as its present channel, vast chambers formed by the excavation of thousands of tons of the hard Conglomerate, great halls over 70 feet in height and of fine proportions. The process which formed these is still at work enlarging them, till in the course of time they must collapse; yet no change is ever visible, no signs of recent action can at any point be seen. The rarely occurring great flood serves but to remove one film of sand from the floor and to leave another in its place as the waters subside. So slow is the undermining action that no eye can ever detect a change though the waters rise ever so high. Yet this channel is but one of five distinct levels which the river has occupied from time to time, until it has found in turn a lower course, leaving its sands as a record upon each, here and there sealed down beneath a mass of stalagmite. What untold ages have elapsed since first the river flowed through these upper channels!

PLAN AND SECTION OF WOOKEY HOLE CAVERN.

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

But an examination of the top of the Mendips points to a vaster antiquity still. The published horizontal section No. 17 of the Geological Survey gives an excellent idea of the plateau of Mendip, which stretches from immediately north of Wells to the neighbourhood of Compton Martin. This plane of denudation would never have been reached save by the long-continued action of subterraneous streams, an assumption supported by the existence of the great depression crossed by the road from Wells to Priddy. That depression of nearly 100 feet in depth and several miles in length, hollowed in the hard Carboniferous Limestone, here dotted with every known type of swallet or swallow hole, has been obviously formed by the slow action of swallet streams prolonged through vast periods of time. Every atom of the millions of tons of solid rock represented by this depression has been borne down the course of the subterranean Axe. Tributary to this depression a little valley has been eroded across the Old Red Sandstone anticline immediately to the north, and in it are deposited masses of Dolomitic Conglomerate, the component pebbles of which were derived from the surrounding rocks. The same valley existed, therefore, in pre-Triassic time, and as there was obviously no other outlet for its water, the cavities into which it flowed—that is to say, the swallets and subterranean channels—must have existed also, and are therefore pre-Triassic in date. Though at first sight this appears impossible, inasmuch as the known course of the resulting Axe River is through Triassic Conglomerate, I propose to show that such a conclusion is necessary and inevitable. Long ago I was struck with the fact that at Wookey Hole the Triassic Conglomerate attains an abnormal thickness, and measurements have shown that at the far end of the cavern there is certainly a thickness of over 350 feet of this rock. As there is no sign of any approach to the Limestone against which it must abut, nor any change in the character of the Conglomerate itself at this point, I think that we may fairly conclude that the total thickness of it must be at least 500 feet. Now this is a vast deposit, far exceeding any known to exist elsewhere, and it requires a special explanation to account for it. Only one explanation is possible. The Conglomerate is here filling in some great pre-existing valley in the Mountain Limestone. That is just what I should expect.

The great Limestone cavern formed by the action of the swallet streams in early Triassic times collapsed, and formed a Limestone ravine, into which was rolled a great accumulation of fragments of the Limestone derived from the slopes and crags above. With the whole of this part of England these beds were subsequently submerged, remaining so during the deposit of the whole of the Secondary beds; and on their emerging once more from beneath the sea the lines of drainage were re-established along the old courses, where these had not been choked with sedimentary material. Forcing a way through the Conglomerate which then impeded its flow, the river formed those cavities which we see. Indeed, it may well be that the successive levels cut by the Axe through the Conglomerate may represent stages in the uplifting of the land, the lowest channel being the last and largest, as it has been formed during an extended period of stability. But we are not without evidences of another sort as to the existence of some of our swallet ways at that remote period. The cavities found in the Holwell quarries, near Frome, filled in with Rhaetic material containing bones and teeth of fishes; those of Gurney-Slade, near Radstock; and numbers which from time to time are laid bare in the Limestone quarries, all filled in with Triassic sediment, show that penetrating waterways of considerable size then existed. There was, too, at Charterhouse-on-Mendip, north of Cheddar, a fissure, possibly a swallet, which, being open, received an infilling of Liassic material that is known to extend to a depth of 300 feet. Had these channels been closed by a narrow aperture temporarily blocked, no infilling but by water would have taken place when the land sank beneath the waters of the Triassic and Liassic seas.

Furthermore, in the position of the entrances of many of our swallets there is corroborative evidence to the same effect. The great circular swallet on Rookham, near Wells, situated far from any existing line of drainage, yet withal one of the largest cavities on Mendip, shows that great changes have taken place since it was an active waterway. The position of the caverns of Compton Bishop and of Banwell, far removed from any stream or any line of drainage possible with the present contours, proves that the configuration of the country has utterly changed since they formed the points of engulfment of any streams. The Coral Cave (as we have called it) at Compton Bishop descends abruptly into the earth, and its outlet must have been far below the level where now the Triassic Marl forms an impervious barrier. The waters of Banwell Pond rise through the Marl, forced upwards through beds which do not yield water and ordinarily retard its passage. Doubtless the Marl when it was deposited covered some earlier outlet from the Limestone. The waters of St. Andrew's Well, at Wells, are forced upwards through Dolomitic Conglomerate and overlying Pleistocene gravel, the former of which was doubtless deposited upon what was once a free and unimpeded outlet from the Mountain Limestone, similar to that of Cheddar. The water of Rickford, near Burrington, resulting from the streams engulfed at and around Burrington, is forced up through the Secondary beds, which have been similarly deposited upon the pre-existing outlet. All these things help to demonstrate that what I contend is true, viz. that our caverns as a whole are pre-Triassic in age. The Long Hole at Cheddar, high in the cliffs above Gough's Cave, lends its evidence too. Contrary to all the other caves at Cheddar, it was a channel of intake for the water which formed it. Doubtless it is a fragment of a larger cavern, which, before the gorge of Cheddar itself was formed, existed in the mass of rock occupying the whole area. At the northern end of the Limestone defile of Ebbor, near Wells, the ravine is carved through Dolomitic Conglomerate, which has been much worked for iron ore. The fact that this Conglomerate was deposited in a depression in the land, at the head of the present ravine, yet without entering it, suggests that here was an entrance to a series of caverns, the collapse of which produced the gorge.

THE GREAT SWALLET ON BISHOP'S LOT, PRIDDY

Photo by Bamforth, Holmfirth

ST. ANDREW'S WELL, WELLS.

Photo by H. E. Balch.

The Devil's Punchbowl, near the Castle of Comfort Inn on the Mendips, is, in all probability, a collapse of the remarkable Lias beds which there occur into some pre-existing cavity in the Mountain Limestone below, somewhat in the same manner as the Shake Holes in the Glacial Drift on the Yorkshire moors were formed. No one questions the existence of the cavities beneath before the deposit of the Drift, neither do I doubt the existence of swallets beneath the Trias and Lias before these were deposited on the Mendips. The question naturally arises, Why do we not find in our caverns remains of all the ages that have elapsed since that time? Why are only Pleistocene remains discovered? Surely, because we have not found them it does not follow that they are nonexistent. The recent discovery of Pliocene remains in a cavern at Doveholes, near Buxton (Derbyshire), is clear proof that we may search hopefully for similar remains in the Mendips. It must be borne in mind, that the further we go back in time, the more certain we are to find that the contents of any Limestone cavern would be completely mineralised, until the whole of the contents may have become cemented into a solid mass. Where running water is present, attrition may have destroyed them, or borne them onwards to those great depths where, constantly submerged as they must be, we can never hope to penetrate. I am aware, however, of the existence, in the Eastwater Cavern, of very ancient chokes of water-borne material, from which I have some hope of obtaining remains.

I might mention the demonstrated antiquity of the bosses of stalagmite in Kent's Cavern at Torquay, and from it argue the immense age of the great masses of stalagmite in the Mendip Caves, but, recognising the variable rate of deposit of the carbonate of lime in different caverns, and indeed in different parts of the same cavern, no useful purpose would be served thereby. The huge Beehive of Lamb's Lair at Harptree, the large boss in the first great chamber at Wookey Hole, Gough's "Niagara" at Cheddar, the tall and slender pillars in Cox's Cave at Cheddar, and the taller "Sentinel" pillar at Wookey Hole, all demand for their formation a prodigious length of time, which it is but folly to attempt to compute with our present information. Certainly many thousands of years are required for some of them, and it should be remembered that we have then arrived merely at the time when the floor upon which they stand had received its final form, the action of running water having ceased.[2] Who can doubt then, that, as we stand in the great waterways of the profound depths of our hills, we are looking upon scenes which have varied little since remote ages, and that in some form or other these waterways played an important part in the degradation of the earlier and loftier Mendip range?

It is worthy of remark in this connection that the veteran M. Martel, commenting upon the caverns of Mendip, says, "In consequence of the existence, on the flanks of the Mendip Hills, of deposits of Triassic Dolomitic Conglomerate (Keuper) of Rhaetian beds, and of possibly Glacial alluvia, unconformably on the Carboniferous Limestone, the outflow of the water in the risings operates in three ways: (A) by large fissures in the Limestone itself, when it flows out freely, as at Cheddar; (B) through the crevices in the Dolomitic Conglomerate (the Axe at Wookey Hole, etc.); (C) where the outlet of the water from the Limestone is hidden by alluvia (St. Andrews Well, at Wells). The consequence of this arrangement is that it will be possible—notably at Wookey Hole, when the explorations now going on have enlarged the new galleries recently found—to ascertain whether the Dolomitic Conglomerate is there shown in long beds of ancient shores, regularly superposed on the Limestone, or rather accumulated in filled-up pockets, in hollows pre-existing in the Limestone; that is to say, there will be a material verification of Mr. Balch's hypothesis (already outlined by Boyd Dawkins in 1874) of the very ancient excavation of certain caves of the Mendip Hills, even before the Keuper period. The lie of the Conglomerate under the vaulted roofs of Wookey Hole appeared to me to favour this idea. And it is necessary to wait till formal proofs have been gathered together here, that caves were hollowed out there before the Trias. I recall, on this subject, that long ago I concluded, with Messrs. De Launey, Van den Broeck, Boule, etc., that the formation of caves could commence in the most distant geological epochs, and that the pockets of phosphorites, among others at Quercy and the Albanets of Couvin (Belgium), testify to caves or abysses of at least Eocene times."

H. E. B.