THE SUBTERRANEAN RIVER.
The first object of interest in the right-hand branch of the Imperial Cave is the Subterranean River, which runs at the bottom of a fearful chasm about 50 yards from the point where the two branches bifurcate. After having wandered through marble halls and crystal palaces, and bowers where "rural fays and fairies dwell," the course seems rather gloomy. But attention is attracted by some curiously-shaped nodules, like those found in a part of the Arch Cave, and by basins with thin laminated sides slightly corrugated. These specimens reveal the secret of the construction of the pretty reticulated mounds, which give such a charming effect to several of the most regularly formed features of the caves. To complete the process, the sharp parallel lines which form a succession of little equidistant ridges require only to be smoothed off by a gently flowing film of water, and to receive a coat of colouring derived from clay or oxide of iron. This part of the branch, therefore, should not be passed through hurriedly, for it is instructive.
THE UNDERGROUND RIVER AND ITS REFLECTIONS.
The road is fairly good, although the arching is low. Those parts, the narrowness of which formerly made progress difficult, have been enlarged, but a pretty natural bridge has been carefully preserved. The halt is at the end of a wire ladder bent over a cliff, which forms one side of an immense gulf, where perpetual darkness broods. Here the visitor has a more ungraceful task to perform than that of the cursed serpent, for he must recline face downwards and "progress backwards" until he assumes the form of an obtuse angle, with one line over the precipice. Then he has to use his legs pretty much as an octopus uses its tentacles, to gain a footing on the ladder, which descends about 50 feet on the chasm side of the angle. Having found the first rung he feels happy, but not sufficiently hilarious to slide like a lamplighter. He grips the side wires carefully, takes heed to his steps, and goes down slowly. When he has descended a little way, the dim candle-lights above appear to be far distant, and when he is 20 or 30 steps down they look like glowworms. The journey, however, is not perilous to persons who possess a fair share of agility and nerve. It is frequently performed by ladies, of whom the guide is specially careful, preceding them and keeping just below them on the ladder. As this is, perhaps, the most interesting of all the cave sights, it is desirable that some easy mode of descent should be provided, such as a skip like those employed in mines, or a lift made by machinery to work as easily and effectively as those which ascended and descended at will in the subterranean world inhabited by "the coming race." It was, perhaps, some such place as this which suggested to Bulwer Lytton the chasm down which his nameless hero descended to the bottom of an abyss illuminated with a diffused atmospheric light, soft and silvery as from a northern star; where he found lakes and rivulets which seemed to have been curbed into artificial banks, some of pure water, and some which shone like pools of naphtha; where the birds piped in chorus, and where he made the acquaintance of the An people and the Gy-ei, who moved through the air without effort, who had for servants automata always obedient, and totally ignorant of the eight-hours system, and whose religion had these two peculiarities: "Firstly, that they all believed in the creed they professed; and, secondly, that they all practised the precepts indicated by the creed."
Underground rivers appear to be natural to limestone caves. The reason of their existence is to be found in the fact that the mountains in which they are formed are, in geological parlance, "dykes." They must not be confounded with old river beds, such as are encountered by miners—where the surface of the earth has been raised by deposits of alluvium, or where the geological condition of things has been changed by volcanic action. These cave rivers have all been formed by water finding the lowest attainable level in its passage to the sea, and by the solid limestone rocks which have barred its direct course, and have been undermined by its subtle but persistent action. The fluid, dammed back by the mountains, has simply obeyed the laws of gravitation and accumulated force, as evidenced in the trickling silvery thread which follows the course of ant-tracks; in the laughing rill which makes its bed among the pebbles; in the babbling brook which leaps to the swelling river; and in the mighty torrent whose strength and velocity proclaim the majesty of hydraulic power. In all parts of the world where limestone dykes and caves exist, it is reasonable to expect to find subterranean rivers. The eye of the seer can follow the water drips—
"Down through caverns and gulfs profound,
To the dreary fountain-head
Of lakes and rivers underground."
He can see them again when the rain is done—
"On the bridge of colours seven,
Climbing up once more to heaven,
Past the setting sun."
But the underground rivers found in caves perform vagaries outside the sweet imaginings of the poet and the prevision of the seer. Far from the beaten track they turbulently force their way through recesses and tunnels and pockets of the earth, before they are again warmed with sunshine, and glow in the harmonious colours which form the Bow of Promise.
The Rev. Richard Taylor, in his "Te ika a maui," refers to interesting caves near Mokau (New Zealand), in some of which bones of the moa have been discovered. About a mile from Pukemapau he came to a limestone range, and entered a large cave called Tanaureure. At the bottom of a chasm he found a fine crystal spring, about a foot or so deep, but appears not to have been particularly inquisitive as to whence the water came or whither it went.
A little distance up one of the tributaries of the Rewa River, in Fiji, is a crystal streamlet which flows on towards a lofty ridge, near to which it sinks into the earth. At the mouth of a dark cavern can be heard the roaring. It is a grand expansive excavation, but
"Dark as was chaos ere the infant sun
Was roll'd together, or had tried his beams
Athwart the gloom profound."
The water rushes through narrow chasms as through a race, collects in a large pool, and flows through a distant outlet, marked by a speck of light, like a tiny star.
At the Weathercote Cave, in Yorkshire, a stream swallowed up by a rocky mouth is thus described by Walter White in his book entitled "A Month in Yorkshire":—
"The rocks are thickly covered in places with ferns and mosses, and are broken up by crevices into a diversity of forms, rugged as chaos. A few feet down, and you see a beautiful crystalline spring in a cleft on the right, and the water turning the moss to stone as it trickles down. A few feet lower, and you pass under a natural bridge formed by huge fallen blocks. The stair gets rougher, twisting among the big, damp lumps of limestone, when suddenly your guide points to the fall at the farther extremity of the chasm. The rocks are black, the place is gloomy, imparting thereby a surprising effect to the white rushing column of water. A beck running down the hill finds its way into a crevice in the cliffs, from which it leaps in one great fall of more than 80 feet, roaring loudly. Look up: the chasm is so narrow that the trees and bushes overhang and meet overhead; and what with the subdued light and mixture of crags and verdure, and the impressive aspect of the place altogether, you will be lost in admiration.
"To descend lower seems scarcely possible, but you do get down, scrambling over the big stones to the very bottom, into the swirling shower of spray. Here a deep recess, or chamber, at one side, about eight feet in height, affords good standing ground, whence you may see that the water is swallowed up at once, and disappears in the heap of pebbles on which it falls."
In the Wombeyan Caves, near Taralga, in this colony (New South Wales), there is a similar phenomenon. The mountain in which the caves are formed dams, at right angles, a valley of considerable length. On the one side a creek flows into a hole underneath the "Wombeyan Church"—a name given to the principal entrance. This shallow hole is filled with large boulders and less bulky water-worn stones, through which the water instantly filters and disappears. The suction is perceptible if a hand or foot be placed in the basin. On the other side of the mountain the water, running at a considerable distance below the surface, can be seen through an orifice. Farther on, about three-quarters of a mile from the mountain side, the stream bubbles up like a fountain, and reminds the visitor of antique pictures representing the rush of water from rock-smitten Horeb.
The most gigantic of underground river wonders are to be found in the Mammoth Cave of Kentucky, where the Echo River is navigable for three-quarters of a mile, where the Roaring River raises its liquid voice, where Lake Lethe soothes to forgetfulness, and where there is a veritable Styx with a nineteenth century Charon. But although everything about that cave is colossal, it cannot surpass Jenolan in its deep emotional effects, or in the admiration it evokes. Indeed, in these respects an American visitor, familiar with the Mammoth Cave, has given the palm to Jenolan.
Having descended the 50-feet ladder, the foot of which is clamped to a bare rock, the excursionist watches the guide hopping gleefully down, with candles in one hand and paraphernalia in the other. He then peers into the darkness to find the river, and is led along a gradual slope of about ten feet, when he comes to its margin without recognising it, and would possibly soon be up to his knees in it if he were not warned by his cicerone. It is apparently motionless, as smooth as a mirror, and so clear that at first it is difficult to believe there is any water there at all. You see the sand and pebbles and rocks at the bottom, but do not perceive the fluid which covers them.
The river is about 10 feet wide, and from 12 to 18 inches deep. The length visible is about 60 yards. The overhanging rocks range from 5 or 6 feet to 70 feet in height. From one end of the river comes a sweet soothing sound, made by water-friction. This proves the existence of a considerable current, but the fluid is so limpid and smooth that the eye cannot detect its motion. It is demonstrated, however, in another way. The curator cuts little sections of sperm candle, and, after lighting the wick, floats them on the river, whereupon they immediately begin to glide down the stream, the course of which is nearly south-east. The effect is extremely pretty. Not only are the lights themselves sharply mirrored below, but there is a perfect reflection of the rocks above. Near the tunnel by which the water emerges N.N.W. is a mass of overhanging formation, duplicated in a natural mirror. The bed of the watercourse is dark, being covered chiefly with mud and grit and a few water-worn pebbles. The rocky walls are of limestone—white and black. Up the channel N.W., about 40 yards, is a good crossing-place—not in old Charon's boat, but by means of an ordinary deal plank. On the other side of the river is a ledge of rocks with pebble drift concreted with a substance somewhat resembling the cement in which diamonds are found, and the pebbles, although larger, are of the same shape and blackness as those commonly associated with the luminous gems found in their natural state at Kimberley, in South Africa, or in the Tenterfield district of New South Wales.
On turning the light of the magnesium lamp up the river, its rocky ledges are seen to be ornamented with stalactites and formation perfectly mirrored in the water, which is about 600 feet from the surface, and about 50 below the level of the Cave House in the centre of the valley. Never had river more romantic barriers. Human imagination could not conceive a freak of nature more wildly grand or mysteriously beautiful. There are large ornamented pillars near delicately-tinted formation, drooping from overhanging rocks, like pensile boughs of weeping willow. Some of the twigs skim the surface of the stream, and others are bathed in it. Beyond is a water-hole about 40 feet long, and from 16 to 20 feet wide. Because of its wonderful clearness, it is difficult to judge of its depth; but it has been tested to the extent of five feet, and probably at the extreme point where the water flows from the tunnel it may be six or seven feet deep. The effect of the brilliant light is superb. The ornamentation on the roof of the tunnel is reflected and transposed in the mirror below, each reflected stalactite having the appearance of a twin stalagmite rising from the river bed, which may be traversed for about 150 yards.
Nearly six months ago the caretaker placed in this river twenty young carp from Bathurst. Some of them were enticed from their cavernous resting-places by the bright rays of the lamp, and appeared to be tolerably vivacious and in fair condition. They seem to have all they require except the solar rays; but what is life without sunshine! They ought to be scientifically observed, for there is a theory that in three generations of darkness they will become blind. This has been the fate of the fishes in the Mammoth Cave of Kentucky, and it is stated that their blindness is the result of a law of Nature, which does not continue to supply organs or powers which have ceased to be necessary. Dr. Forwood, in his history of the Mammoth Cave, says:—"The fishes are of a peculiar species, and are of a class known as viviparous, which give birth to their young alive, and do not deposit eggs after the manner of most other fishes. They have rudiments of eyes, but no optic nerve, and are, therefore, incapable of being affected by any degree of light.... It has been proved that these eyeless fishes prey upon each other. In shape they somewhat resemble the common catfish, and rarely exceed eight inches in length." Professor Silliman published the following in his "Journal" for May 1851:—"Of the fish there are two species, one of which has been described by Dr. Wyman in the American Journal of Science, and which is entirely eyeless. The second species of the fish is not colourless like the first, and it has external eyes, which, however, are found to be quite blind. The crawfish, or small crustacea, inhabiting the rivers with fish are also eyeless and uncoloured; but the larger-eyed and coloured crawfish, which are abundant within the caves, are also common at some seasons in the subterranean rivers, and so also, it is said, the fish of the Green River are to be found in times of flood in the rivers of the Caves." Dr. Forwood gives also the following quotations, on the authority of Professor Agassiz, an eminent naturalist in the department of ichthyology:—
"The blind fish of the Mammoth Cave was for the first time described in 1842 in the 'Zoology of New York,' by Dr. Dekay, part 3rd, page 187, under the name of 'Amblyopsis spelæus,' and referred, with doubt, to the family of 'Siluridæ,' on account of a remote resemblance to my genus Cetopsis. Dr. J. Wyman has published a more minute description of it, with very interesting anatomical details, in vol. xlv. of the 'American Journal of Science and Arts,' 1843, page 94.
"In 1844, Dr. Tellkampf published a more extended description, with figures, in 'Müller's Archiv' for 1844, and mentioned several other animals found also in the Cave, among which the most interesting is the crustacean which he calls 'Astacus pellucidus,' already mentioned, but not described, by Mr. Thompson, President of the Natural History Society of Belfast. Both Thompson and Tellkampf speak of eyes in these species, but they are mistaken. I have examined several specimens and satisfied myself that the peduncle of the eye only exists; but there are no visible facets at its extremity, as in other crawfish.
"Mr. Thompson mentions, further, crickets, allied to 'Phalangopsis longipes,' of which Tellkampf says that it occurs throughout the Cave. Of spiders, Dr. Tellkampf found two eyeless, small white species, which he calls 'Phalangodes armata' and 'Anthrobia monmouthia'; flies, of the genus 'Anthomyia'; a minute shrimp, called by him 'Triura cavernicola'; and two blind beetles; 'Anophthalmus tellkampfii' of Erichson, and 'Adelops hirtus;' of most of which Dr. Tellkampf has published a full description, and figures in a subsequent paper, inserted in Erichson's 'Archiv,' 1844, p. 318.
"The infusoria observed in the Cave resemble 'Monas Kolpoda,' 'Monas socialis,' and 'Bodo intestinalis,'—a new Chilomonas, which he calls 'Ch. emarginata,' and a species allied to 'Kolpoda cucullus.'
"As already mentioned, Dekay has referred the blind fish, with doubt, to the family of Siluridæ. Dr. Tellkampf, however, establishes for it a distinct family. Dr. Storer, in his 'Synopsis of the Fishes of North America,' published in 1846, in the 'Memoirs of the American Academy of Arts and Sciences,' is also of opinion that it should constitute a distinct family, to which he gives the new name of 'Hypsæidæ,' page 435. From the circumstance of its being viviparous, from the character of its scales, and from the form and structure of its head, I am inclined to consider this fish as an aberrant type of my family of Cyprinodonts."
The effect of long-continued darkness upon visual organs has had some remarkable illustrations. At one time an idea prevailed in America that caves possessed certain curative properties, and afflicted people remained in them; but the absence of light proved disastrous to many. It is recorded that those patients "who remained in the cave three or four months presented a frightful appearance. The face was entirely bloodless, eyes sunken, and pupils dilated to such a degree that the iris ceased to be visible, so that, no matter what the original colour of the eye might have been, it soon appeared black."
This subterranean river offers a fine opportunity for scientific observation well worthy to be embraced by some Australian naturalist. In the vicinity of the river is to be noticed one of the few signs of decay to be found in the caves—a portion of shell pattern formation shows evidence of mouldering, and appears like a mere skeleton. When the visitor has ascended the ladder and safely negotiated the angle at the top, he feels that he has witnessed the most interesting place to be found in the western wonderland; and when he fishes for a compliment to his agility, and is reminded of the graceful forms that occasionally ascend and descend in much better style, he immediately recalls a Patriarch's dream, and thinks the ladder ought to be named after Jacob.
