across the tunnel which was once the bed of a subterranean river, but which is now a broad, smooth, dry path.

The topography of this underground realm may be divided into three departments, as follows:

First, as being greatest in extent, -the "avenues," or tunnels, which present conclusive evidence of having once been the channels of a subterranean stream, whose waters, having some peculiar solvent property, wore their bed lower and lower in the rock, until they cut through into some lower opening, through which they were drawn off, leaving the old channels dry. Imagine one of the narrow, crooked streets in the old part of Boston, spanned by a continuous stone archway from the summits of the buildings on either hand; then close with solid masonry every window and loop-hole by which a ray of light could struggle in, and you have for proportions and sinuosity not a bad semblance of these tunnels, which constitute four fifths of the extent of the Mammoth Cave.

The second and next largest department is that of the "chambers." These are places in the general course of the former river where the roof fell in before the withdrawal of the waters, opening great spaces upward; the fallen mass forming a sort of island in the centre of the stream, and crowding the waters on either side of it against the walls of the cave, so that they were worn out to twice the average width, and finally itself disappearing under the combined action of the current and the solvent properties of the water.

The air in all these tunnels and chambers is remarkably dry and pure. Wood seems never to decay here; as is instanced in the wooden pipes and vats of the saltpetre-makers, upon which the lapse of a half-century has not had any visible effect.

The general width of the tunnels or avenues is about forty or fifty feet, and the average height about thirty feet; but this uniformity is broken every few hundred yards by chambers, varying in width from eighty to two

hundred feet, and in height from seventy to two hundred and fifty feet. The floor is formed in some places of sand, but generally of indurated mud, so hard that it is impossible to make any indentation in it with the heel of the boot, and remarkably even and smooth, so that almost anywhere one can walk with as much ease as on city sidewalks. The walls also are clean and smooth, as in the arched crypts of some mighty cathedral. A cross section of almost any one of these tunnels would show an elliptic outline, the vertical diameter being the shortest, and the bottom being filled with indurated mud or sand to a sufficient depth to make a level floor.

The third division or class of openings is that of the "domes" and "pits." These were formed by the same kind of agency as the tunnels and chambers, namely, by the action of water holding carbonic acid in solution; but acting in a different manner, and at a period long after the subterranean river had ceased to flow through its tunnels.

The solvent acid of the water must be acquired in percolating through the several hundreds of feet of superincumbent earth and sandstone, as there is but one of these domes, "Sandstone Dome," that extends upward to the sandstone. The solvent water then, after finding its way into the vertical crevices of the limestone, gradually rounded them out like wells, until the pieces which occasionally fell from the top formed a sort of floor. Through the interstices of this floor, the dissolved substance of the rock is carried into some deeper and yet undiscovered cavities beneath. The floor itself gradually sinks, the domes grow higher, and the walls recede as long as the water continues to drip into them.

It is not unreasonable to suppose that the substratum of limestone in all the country for many miles in the vicinity is perforated with these tremendous shafts; as those which are seen in the cave are only such as happened to be in the course of the tunnels composing

the Mammoth Cave. It is not improbable that there are many others on every side, close to the line of the tunnels, but not yet connected with them.

In any one of the above-mentioned departments, the description of one place answers for most others, except in dimensions. The following are a few out of many hundreds of measurements taken in as many different places :

The "Rotunda," the first chamber from the entrance of the cave, is about one hundred feet high, and one hundred and seventy-five in diameter.

The "Methodist Church," eighty feet in diameter, and forty in height.

"Wright's Rotunda" is four hundred feet in its shortest diameter, being nearly circular; the roof seems perfectly level, and is about forty-five feet high.

Although the distance of nine miles is about as far as tourists usually get from the entrance, that is by no means the measure of its extent, but only the extent of the direct route; there being a number of other tunnels branching off from it on either side, some of which connect with it again at a distance of several miles, and some of which have not been explored to their connection, if they have any.

The total length of all the explored avenues is estimated at over one hundred miles. If a single day's experience in the cave were sufficient ground for offering an opinion, I should say that this was a large over-estimate ; but I have no doubt that, like all other great works of both art and nature, it grows upon the sense of the beholder. But even setting down its extent at

tread these hollow chambers, thinking of others unexplored, and extending not only from that distant nine-mile-station, but on every hand, into the unknown, without a feeling of awe and fear.

Thus on and on through the echoing avenues, where the reverberation of our footsteps seemed to follow stealthily far behind us, through chamber and hall, where my guide in the advance flung up his lights, revealing for an instant the grim and distant vaults, - through "Star Chamber," five hundred feet long, seventy in width, and sixty in height, "Cloud Room," a quarter of a mile in length, sixty feet in height, "Deserted Chamber," " River Hall," "Revellers' Hall," "The Great Walk," through all these, and a dozen more, we wandered, until, after two hours' walk, and at a distance of four and a half miles from the entrance to the cave, I paused upon the muddy banks of the "Styx," and, stooping, dipped up in my hands a draught from its cold, sunless waters.

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Here my guide would willingly have played Charon to my Ulysses, but as no one had penetrated thus far into the cave for several months, the boat used to carry visitors over, and to voyage up and down the short river (only a

hundred and fifty yards in length), had sunk, and we found it impossible to raise it.

The river is about twenty-five feet in width, its course crossing that of the cave at right angles, and its channel being simply another avenue or tunnel on a little lower level than the one by which the visitor approaches it.

In this stream, as well as in "Echo River," are found the famous eyeless fish. We dipped in vain, for a long time, in hopes of capturing some of these. At last I was fortunate enough to secure one tiny specimen, about two inches long, which was shaped like other minnows, but had no eyes, and was perfectly white, there being not the slightest shade of coloring on the back. The upper part of its head was as translucent as agate, through which could be seen opaque spots imbedded in the head where the base of the eye-sockets should have been. The specimen I obtained was one of the smallest, as the guide told me these fishes frequently attained the length of six or seven inches. I secured also an eyeless crawfish about three inches in length. This forlorn little creature, like the fish, was entirely colorless. It had two slightly protuberant spots in its head where the eyes should be; but they were dull and opaque, and did not seem to differ in texture from the rest of its body, which had not the translucence of that of the fish, but looked as though carved out of white marble.

The fish are found also in "Lake Lethe," a quarter of a mile from the Styx, as well as in "Echo River," the largest and most interesting body of water in the cave. This last flows out of a tunnel which has such a low roof that the volume of water nearly fills it, and from here to where it enters the rocks again is three quarters of a mile. Here the blind white creatures that inhabit its dark, slow-flowing waters are more plentiful, but are as unlike those nimble, glistening fellows which inhabit the streams of the outer world, as the cavern's atmosphere of darkness and death is different from our

atmosphere of light and life. They refuse to bite at any bait; they move sluggishly, and, when caught in a net, flop languidly, and die. The only food they are known to have is the smaller ones of their own kind; and, oddest of all, they, as well as the crawfish, give birth to their young alive, instead of spawning the eggs to be hatched by the sun. Last and remotest of these sunless streams is " Roaring River," the margin of whose solemn waters is nine miles from the entrance of the cave. This should be Acheron, which hated the light, and ran sighing down into a cave; for from this stream too comes a perpetual moan.

The region where the several rivers mentioned are grouped is lower than the rest of the cave, and much more gloomy in appearance than the high, dry chambers through which one passes in coming back toward the entrance.

I was somewhat disappointed in the display of stalactites and other similar formations of the protocarbonate of lime found in the cave. For a number of years I had been familiar with mines and mining operations in the lead-mining districts of Illinois, Wisconsin, and Missouri, and had there seen some of the most beautiful, though not the largest, specimens of calcareous spar known to exist. The lime in these localities being in most instances perfectly pure, the stalactites, to the length of three feet sometimes, are as free from coloring as icicles. Sometimes the miners' drift (which compared with the Mammoth Cave is as a rabbit's burrow to a railway tunnel) is opened into small, low-roofed caves; and in these, in addition to the translucent stalactites, there are little hollows in the floor covered with thin sheets of protocarbonate of lime, no thicker than a pane of window-glass, and as white as snow. From beneath these the water has sunk away, leaving a hollow space, and giving the whole precisely the appearance of those little pools which every one has noticed when a muddy road suddenly congeals: the pools of water freeze over, and the wa

ter disappears, leaving the ice only a shell over a cavity.

Nothing of this kind, however, is found in the Mammoth Cave. The lime of which the stalactites are formed being mixed with various oxides and other impurities, they are all of a dark brown, or gray, or muddy color. With the exception of some stalactite columns in the "Gothic Arcade," which form a fine alcove called the "Gothic Chapel," there are no stalactites of extraordinary size. There is a stalactite mass (or was some years ago) in "Uhrig's Cave," in the suburbs of the city of St. Louis, about twelve feet in height and four feet in diameter, which exceeds in size anything I saw in the Mammoth Cave.

The gypsum or alabaster flowers are the crowning beauty of the Mammoth Cave. These are an entirely different formation from the stalactites, being formed only in a perfectly dry atmosphere, while the stalactites are necessarily formed in a moist one.

The gypsum is formed by crystallization, and in that process exerts the same expansive force as ice. Wherever it forms in crevices it fractures the rocks that enclose it, and protrudes from the crevice; its own bulk divides, or splits, and curves open, and outward, with much more tenacity than ice. It seems to have a fibrous texture, in the direction of which the split always opens.

I found in the "Snowball Room" and in a large chamber called "Cleveland's Cabinet," a beautiful display of these flowers. In the Snowball Room, the likeness to winter appears again, in the knots strongly resembling snowballs stuck all over the ceiling. And in Cleveland's Cabinet I found some singularly beautiful specimens of alabaster formations. One kind seemed to be literally growing from the ceiling as a vegetable would, and looked more than anything else like short, thick stalks of celery. If an ordinary stalk of celery were split, so that its natural tendency to curl over backward could be freely exercised, it

would give a very good idea of the shape of some of the gypsum flowers, except that these are not often longer than four inches, and in that length frequently curl so as to make a complete circle. They have the same fibrous appearance as celery, and are as white

as snow.

When five or six of these stalks - if I may call them so-start from one point, and curve outward in different directions from a common centre, they frequently form beautiful rosettes. Imagine one of the common tiger-lilies, which, instead of its thin, red curving petals, has stalks of celery, curving as much, but broken off square at the ends; then imagine the celery to be of the purest conceivable white; and you have a tolerable conception of one of these beautiful alabaster flowers.

This alabaster growth is found only in a few places throughout the cave; when it is in chambers or spaces in which the atmosphere is very dry, it invariably has a beautiful fibrous texture like wood or celery, and the curved form; but if the atmosphere is damp, it forms on the ceiling in round nodules, from two to three inches in diameter, as in the Snowball Room.

In the Gothic Arcade there is a sort of colonnade formed along the side of the tunnel by the meeting of the down-growing stalactites and the upward-growing stalagmites; the two together having formed slender columns of spar, from three to six feet in height. One group of these, about eight feet high, which is the most beautiful in the cave, is called the Gothic Chapel. In many of the formations, it is very difficult to trace even the remotest resemblance to the objects after which they have been named ; but in one instance, that of a stalactite called the "Elephant's Head," the resemblance is remarkable.

Ordinarily it is the custom for one guide to conduct a party of four or five persons into the cave. I dislike over - officious guides and the hackneyed comparisons and wordy wonder of gabbling tourists in grand and

solemn places like this; therefore, in the morning, before starting, I congratulated myself that I should be alone, with the exception of the guide, who fortunately seemed thoroughly imbued with the spirit of the place in which he had spent the greater portion of his time for seventeen years.

He was as grave and taciturn as some cave-keeping anchorite. During our inward progress, he had carefully pointed out every place and object of interest, and hurled his blue-lights here and there into domes and pits and cavernous retreats of darkness. But now, on our backward course, he stalked silently and abstractedly before, though he seemed to listen to every step of my feet; for, if I paused or made a misstep, he instantly looked round.

At last he turned, and, looking me curiously in the face, asked whether I thought I should be afraid if left in the dark there a little while. Some people could not bear it, he said, and one gentleman who had consented to the ordeal of darkness had been half crazed by it, and when the guide, who had withdrawn and concealed himself, with his light, returned, the traveller tried first to run away into the darkness, and then, under some strange hallucination, fired his pistol in the guide's face.

I had a suspicion that the effect of the obscurity was exaggerated; I was disposed, moreover, to "try the dark," from curiosity. But I must acknowledge that, when the guide, with that doubting look, repeated his inquiry, I hesitated, asking, "Is there any danger? and from what?"

“Nobody knows, massa," said he seriously; "only some people's nerve can't stan' it, dat 's all."

The mention of that odious word, "nerve" sounded so much like the familiar solicitation, "Try your nerves, gentlemen?" from the electrical-machine man, who is found on the curbstone of some thoroughfare in every city, that for one brief instant the prestige of the great cave was gone.

Poh! I thought, so it is only claptrap after all? "Here, take the lamps,

all of them, matches too, and go away so far that I cannot hear you halloo, even at your loudest. I will sit here until you come back!" So saying, I sat down upon a rock in the Star Chamber; and he, taking the lights, walked away toward the entrance of the cave.

"So then," I thought, "this is the perfect darkness, the total absence of light, which is seldom if ever known above ground; for even in the darkest night and the darkest house there are some wandering rays of light; though they may not be sufficient to enable the eye to distinguish anything, they are there; they penetrate, reflected in a hundred zigzags, into the darkest places of the outer world. But here there are miles between me and the utmost limits of their influence !"

I held my hand before my face, but could not distinguish by sight that it was there. A few pale, phosphorescent gleams, that seemed to be wandering in the air, I was convinced were only the remembrances of the optic nerve, eidolons of the retina; but they seemed to some extent plastic to my thoughts, and ready to become the subjective creations of the brain, outlined in the dark. I could conceive then how the brain, excited by fear, or stimulated by emotion, might multiply these phantasms, moulding them into the likeness of objects and beings that never had any existence in reality. My sense of hearing, too, seemed preternaturally sharpened; I could hear the ticking of the watch in my pocket, the throbbing of my own heart, the murmur of the air in my lungs. I held my breath so that the slightest sound from any other source than my own organism should not escape me; the ringing vacancy in my ears grew more and more painful. Not the remotest breath of any sound, except a faint dropping of water in some distant place! (I could think of none but in that awful place called Gorin's Dome.) It seemed to whisper, "Hush! hush! hush!" Sometimes I could not hear the dropping; for just the same reason that, if one listens intently to the ticking of a clock for ten