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!
[Illustration: PLAN AND SECTION OF WOOKEY HOLE CAVERN.]
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.
[Illustration: THE GREAT SWALLET ON BISHOP'S LOT, PRIDDY.
_Photo by Bamforth, Holmfirth_]
[Illustration: 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?
[2] In 1894 the initials "T. W." were carved by Mr. Willcox of Wells
on the great stalagmite bank in the end chamber of Lamb's Lair. I
added "1894," that in years to come some measure may be obtained
of the rate at which this bank is being formed. I make a rule of
never making an inscription, but in this case I thought that the end
justified the means.
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.
CAVE EXPLORING AS A SPORT
We are called a nation of sportsmen; yet the first criticism we
level against any new sport, not our own, is the question, usually
unanswerable and always irrelevant, What is the use of it? One
may then, with a certain show of propriety, point out that cave
exploring is a sport not entirely lacking in utilitarian or scientific
objects. It belongs, in fact, to that large class which originated
as something else than mere pastime. Mountaineering and hunting are
typical representatives of that class. The earliest mountaineers were
geographers. Cave exploring was first of all taken up as a branch of
archæological and palæontological research, and then as a general
inquiry into the physical nature of caves. But a science that has
discovery as its principal object, and hardships and adventure as
its natural concomitants, is bound to attract as many sportsmen as
scientists. The geographical might be called the sporting sciences.
And so there are now many ardent cave explorers who would blush to be
called speleologists, their sole motive being the enjoyment of the
game, and scientific results purely a by-product. Thus the science of
caves has given birth to a sport that subserves its aims in the same
irregular way as rock-climbing and peak-bagging subserve the aims of
geography, geology, meteorology, and other sciences.
Speleology itself is, comparatively, a new science. Cave hunting, the
search for human and animal remains, has been an important bypath
of scientific investigation since the days of Dean Buckland and
the discoveries recorded in _Reliquiæ Diluvianæ_, 1823. Professor
Boyd Dawkins has in recent decades done still more valuable work
for palæontology. Speleology is a word of both wider and narrower
meaning; in the widest sense covering all kinds of knowledge about
caves, their geography, geology, hydrology, their fauna, their
palæontology. But most speleologists confine their attention to
the physical characteristics of caves. This side of the inquiry
has practical utilities. At Vaucluse, for instance, near Avignon,
M. Bouvier in 1878 explored the channels of a gigantic siphon that
carries the waters of an inaccessible reservoir into the Fontaine de
Vaucluse, a famous "rising." His object was partly scientific, and
partly to determine the nature of this permanent source, so as to
utilise its waters to regulate the level of the Sorgue, to extend the
irrigation system of the neighbourhood, and to secure water-power for
manufacturing purposes. The Katavothra of Pod-Stenami were enlarged by
an enterprising engineer, and protected by iron gratings, after their
subterranean exits had been explored, and so utilised to regulate the
drainage of the marshy plains of Laibach, and to prevent periodical
inundations. In our own country, underground exploration has brought to
light valuable water-supplies, and enabled us to safeguard the public
interests by pointing out sources of pollution. Caves are most abundant
in the districts where those great fissures known as rakes occur,
which are rich in minerals, especially lead, calamine, copper, gypsum,
and fluor-spar. During the short period in which cave work has been
taken up as a sport, discoveries have been made, which of course it is
impossible to particularise, that may be the source of considerable
profit in the future.
The majority of those engaged in this physical exploration of caves
are French. France possesses a Société de Spéléologie, the secretary
of which, Monsieur E. A. Martel, author of _Les Abîmes_, is a most
indefatigable and courageous explorer, and the man who has made the
science an important and a living one. But M. Martel himself awards the
title of "créateur de la spéléologie" to a forgotten predecessor, Dr.
Adolphe Schmidl, who published _Die Grotten und Höhlen von Adelsberg_,
in 1854. In this country, although such brilliant discoveries have
been made of extinct animals and prehistoric relics of humanity, cave
exploring of this kind is a new pursuit. M. Martel says, in _Irlande
et Cavernes Anglaises_, 1897: "In short, the underground of the
calcareous regions of the British Isles may be considered as being,
topographically, very insufficiently known; this is the conviction
impressed on me by my own researches in 1893." Something has been
accomplished since that date. Two or three clubs, consisting chiefly
of climbers, and a few speleologists working independently, have
effected a thorough examination of the great caverns of the Peak, the
extraordinary system of underground waters, huge cavities, and profound
abysses in the West Riding, and the beautiful caverns of Somerset. But
the ground that remains unexplored, the opportunities for adventure and
the possibilities of discovery are such as may probably astonish those
people who think there is nothing of the sort left in Old England.
Caves are formed in calcareous strata by the chemical action of water
laden with carbonic acid, and by the mechanical action of streams. In
consequence of the original structure of the Limestone, the joints of
which run at right angles to the bedding planes, these eroded hollows
have two dominant forms: the vertical pot, swallet, or hole, produced
by the widening of a master-joint; and the horizontal water-channel,
running in the same direction as the line of stratification. But the
strata being commonly tilted, these pits and abysses are often a long
way out of the vertical, and the caverns that follow the strata very
steep. Many of these ancient watercourses are now dry, but others
are still traversed by streams, and present the explorer with most
formidable obstacles. The complete exploration of any cave system would
involve the tracing out of all its passages from the point where the
stream or streams enter the earth to the point of exit. But I know
not a single instance where such a task has been worked out in its
entirety. In many cases the streams enter the ground merely as small
rivulets, and begin to excavate passages practicable to man only at a
considerable depth. "Siphons," or traps, as they ought to be called,
complete or partial chokes, and a variety of other causes, may put
insuperable obstacles in the explorer's way.
Take two of the most important cave problems still awaiting solution,
one in Yorkshire, the other in Somerset. A large beck is precipitated
into the abyss of Gaping Ghyll, 360 feet deep, and emerges from
an opening in the hillside, a mile away, close to the mouth of
Ingleborough Cave, which was itself an earlier exit. Several parties
have descended Gaping Ghyll, and followed the passages at the bottom
to a distance of more than 1000 feet. Then impenetrable water-sinks,
and muddy chambers with no outlet, have been encountered, and the
communication with the lower cavern has hitherto proved undiscoverable.
Both the dry galleries and the canals of Ingleborough Cave have been
explored, with great toil and daring, to a considerable distance
upwards, with similar results; and though many speleologists are
still absorbed in this problem, there is little hope that it will be
cleared up without adopting the drastic and costly measure of cutting
through the obstructions. The other problem is that of Wookey Hole,
the cave in Britain which has the longest history, and which is still
yielding interesting discoveries. A number of streams disappear into
the earth on the Mendip plateau, 2 miles away and 700 feet above, and
find their issue in the source of the Axe at Wookey Hole. Two of the
Mendip swallets have been explored to a great depth. Swildon's Hole,
an exquisite series of terraced galleries and stalactite grottoes, has
been penetrated to a depth of 300 feet. But a more determined attempt
has been made to reach the bottom of the Eastwater Cavern. This was
discovered in 1902 by my friend Mr. Balch, of Wells, by means of
opening the swallet, where a tiny brook ran away through small crevices
in a Limestone ravine. A far-extending cave was thus disclosed, full
of intricate ramifications, that explain in a graphic manner how
new galleries are formed and old ones left dry and deserted, as the
result of floods and partial chokes. We have, in the longest route
discovered in this complicated system, reached a distance of 2000 feet
from the entrance and a depth below the surface of 500 feet. At this
point no absolutely impassable barrier has been met with. There is
reason to hope that we may still advance farther into the mysterious
region between it and Wookey Hole. But the formidable difficulties of
the journey hither have set a limit to endurance. Hundreds of feet
of creeping through steep, narrow, and contorted passages, compared
with which a series of drain-pipes would afford luxurious travelling;
perpendicular drops of 50 and 90 feet, with no convenient ledges at
the top for letting men down; and, in addition, the necessity of
transporting great quantities of tackle to the bitter end of it, have
made a twelve hours' day underground as much as we could stand. The
difficulty may perhaps be got over by means of a subterranean bivouac.
Unfortunately, it would not do to leave the apparatus in position for
long beforehand, as it would deteriorate so rapidly. In Wookey Hole
itself, we have not yet succeeded in reaching a farther distance than
600 feet from the cave mouth; there a submerged tunnel has stood in
the way. But Mr. Balch has thoroughly explored the upper passages that
honeycomb the rock above the known caves; he has discovered a number
of promising galleries, which are being slowly cleared of débris;
and, among them, a series of the most beautiful incrusted grottoes in
Britain. A season of drought may reveal an opening up the river-course.