Ice-caves of St. Georges and St. Livres—Beautiful Ice-stalagmites in the Cave of La Baume—The Schafloch—Ice Cataract in the Upper GlaciÈre of St. Livres—Ice Cavern of Eisenerz—The Cave of Yeermalik—Volcanic Ice-caves—Æolian Caverns of Terni—Causes of the low temperature of Ice-caves.

Some caves, remarkable for an extremely low temperature even in summer, form natural ice-cellars, though unconnected with glaciers or snow mountains, and in latitudes and at altitudes where ice could not under ordinary circumstances be supposed to exist. Besides the interest attaching to these natural curiosities, these ice-caves are sometimes lucrative sources of revenue to their owners, or answer various purposes of use or comfort.

In hot summers, when the supplies of the artificial ice-houses fail in Geneva and Lausanne, the hotel-keepers have recourse to the stores laid up for them by nature in the ice-caves or glaciÈres of St. Georges and St. Livres, situated in the canton of Vaud, on the slope of the Jura. Other ice-caves are made use of as dairies, or as storehouses for cheese; and the quarries of Niedermendig, near the small town of Andernach, on the Rhine, which are likewise remarkable for a glacial temperature, serve as excellent beer-cellars.

To Mr. Browne, who has made them his special study, we are indebted for an interesting account of the ice-caves of France and Switzerland,^[26] which, as may naturally be expected in halls and galleries hung with drapery of transparent silver, not seldom offer scenes of beauty rivalling the most renowned stalactital grottoes.

In the GlaciÈre of GrÂce-Dieu, or La Baume, near BesanÇon, Mr. Browne was particularly struck with three large stalagmites of ice rising in a line across the middle of the cave. The central mass was remarkable only for its size, the girth being sixty-six and a half feet at some distance from the ice-floor, with which it blended; but nothing could be more strikingly lovely than the stalagmite to its right, owing to the good taste of some one, who had found that much ice was wont to accumulate on that spot, and had accordingly fixed the trunk of a small fir-tree, with the upper branches complete, to receive the water from the corresponding fissure in the roof. The consequence was that, while the actual tree had vanished from sight under its crystal covering, the ice with which it was incrusted showed every elegance of form which a mould so graceful could suggest, each twig of the different boughs becoming, to all appearance, a solid bar of frosted ice, from which complicated groups of icicles streamed down. But the mass to the left was the grandest and most beautiful of all. It consisted of two lofty heads, like weeping willows in Carrara marble, with three or four others less lofty, resembling a family group of lions’ heads in a subdued attitude of grief, richly decked with icy manes. Similar heads seemed to grow out here and there from the solid sides of the huge mass, which measured seventy-six and a half feet in girth about two feet from the floor. When this column was looked at from the side removed from the entrance to the cave, so that it stood in the centre of the light which poured down the long slope from the outer world, the transparency of the ice made the whole look as if it were set in a narrow frame of impalpable liquid blue—the effect of light penetrating through the mass at its extreme edges.

Other and no less striking beauties rewarded our subterranean explorer on his visit to the Schafloch or Trou-aux-Moutons, a vast ice-cave on the Rothhorn, in the canton of Berne, which takes its name from the fact that, when a sudden storm comes on, the sheep and goats make their way to it for shelter, though never going so far as the spot where the ice begins. On entering the cave the way lies over a wild confusion of loose masses of stone, which soon, however, begin to be intermingled with ice, until the latter entirely hides the naked rock under a crystal mantle.

‘On either side of the cave was a grand column of ice, forming the portal, as it were, through which we must pass to further beauties. The ice-floor rose to meet these columns in a graceful swelling curve, perfectly continuous, so that the general effect was that of two columns whose roots expanded and met in the middle of the cave. Convinced that internal investigations would prove interesting, I began to chop a hole in one of the pillars about two feet from the ground, and having made an entrance sufficiently large, proceeded to get into the cavity which presented itself. The flooring of the dome-shaped grotto in which I found myself was loose rock, at a level of about two feet below the surface of the ice-floor, on which my guide Christian still stood. The dome itself was not high enough to allow me to stand upright, and from the roof, principally from the central part, a complex mass of delicate icicles passed down to the floor, leaving a narrow burrowing passage round, which was itself invaded by icicles from the lower part of the sloping roof, and by stubborn stalagmites of ice rising from the floor. The details of this central cluster of icicles, and, in fact, of every portion of the interior of the strange grotto were exceedingly lovely, and I crushed with much regret, on hands and knees, through fair crystal forests and frozen dreams of beauty. In making the tour of this grotto, contorting my body like a snake, to get in and out among the ice-pillars, and do as little damage as might be, I yet, with all my care, was accompanied by the incessant shiver and clatter of breaking and falling ice. Having squeezed myself out again through the narrow hole, I now passed between the two gigantic columns, and found that the sea of ice became still broader and bolder, until we came to the edge of a glorious ice-fall, round and smooth and perfectly unbroken, passing down like the rapids of some river too deep for its surface to be disturbed, and plunging majestically into a dark gulf, of which we could see neither the roof nor the end.’

We will now follow Mr. Browne to the Upper GlaciÈre of St. Livres, where the interesting discovery was made that the ice-stream which filled the cave, instead of terminating with the wall of rock at its end, turned off to the right, and was lost in darkness. By tying a candle to a long stick, and thrusting it down the slope of ice, it was further found that the stream passed down at a very steep incline, and poured under a narrow and low arch in the wall of the cave, beyond which nothing could be seen. Steps were now cut down the slope by one of the party, who was carefully let down, and, his work being completed, the others followed him through the arch—a rather awkward undertaking, for, on pushing through, their breasts were pressed on to the ice, while their backs scraped against the rock which formed the roof.

‘As soon as this trough was passed,’ says Mr. Browne, ‘the ice spread out like a fan, and finally landed us in a second cavern, 72 feet long by 36 feet broad, to which this was the only entrance. The breadth of the fan at the bottom was 27 feet, and near the archway a very striking column poured from a vertical fissure in the wall, and joined the main stream. The fissure was partially open to the cave, and showed the solid round column within the rock: this column measured 18½ feet in circumference, a little below the point where it became free of the fissure, and it had a stream of ice 22 feet long pouring from its base. The peculiar structure of the ice gave the whole mass the appearance of coursing down very rapidly, as if the water had been frozen while thus moving, and had not therefore ceased so to move.... At the farthest end of the cave, a lofty dome opened up in the roof, beneath which a very lovely cluster of columns had grouped itself, formed of clear porcelain-like ice, and fretted and festooned with the utmost delicacy, as if Andersen’s Ice Maiden had been there in one of her amiable moods and had built herself a palace.’

In Upper Styria, the Frauenmauer Mountain, which overlooks the mining town of Eisenerz, contains a remarkable ice-chamber, consisting of a grotto from thirty to forty fathoms long, decked with ice-crystals, pillars of ice, and cascades of the same material, the floor being composed of ice as smooth as glass. In the summer pleasure parties assemble in the cave, and amuse themselves with sliding down its sloping ice-floors.

In his work on the Natural Wonders of the Austrian Empire, the naturalist Sartori describes his visit to an ice-cave on the Brandstein, a peak situated in the same district, which thus appears to be rich in glaciÈres. He found crimpons necessary for descending the frozen snow, which led from the entrance to the floor of the cave, where he discovered pillars and capitals and pyramids of ice of every possible shape and variety, as if the cave had contained the ruins of a Gothic church or a fairy palace. At the further end, after passing large cascades of ice, his party reached a dark grey hole, which lighted up into blue and green under the influence of the torches; they could not discover the end of this hole, and the stones which they rolled down into it seemed to go on for ever.

Other natural glaciÈres are also mentioned as occurring in Bohemia, Hungary, the Harz, in several places in North America, and probably there are few mountainous regions without them.

The Cave of Yermalik, already mentioned among the silent retreats of nature which have been rendered infamous by the cruelty of man, is likewise highly interesting as a natural glaciÈre. After leaving the roomy dome in which they found the skeletons of the victims of Genghis Khan, Captain Burslem and Lieutenant Sturt proceeded through several low arches and smaller caves, and reached at length a vast hall, in the centre of which was an enormous mass of clear ice, smooth and polished as a mirror, and in the form of a gigantic beehive, with its dome-shaped top just touching the long icicles which depended from the jagged surface of the rock. A small aperture led to the interior of this wonderful congelation, which was divided into several compartments of every fantastic shape. In some the glittering icicles hung like curtains from the roof; in others, the vault was smooth as glass. Beautifully brilliant were the prismatic colours reflected from the varied surface of the ice when the torches flashed suddenly upon them as they passed from cave to cave. Around, above, beneath, everything was of solid ice, and being unable to stand on account of its slippery nature, they slid, or rather glided mysteriously, along the glassy surface of this hall of spells. In one of the largest compartments the icicles had reached the floor, and gave the idea of pillars supporting the roof.’roof.’^[27]

Rocks of volcanic formation seem to afford favourable opportunities for the congelation of water. Ice-caves are found in Mount Etna, on the Peak of Teneriffe, and among the lava-currents of Iceland.^[28] Scrope visited one of these natural glaciÈres near the village of Roth, in the neighbourhood of Andernach, on the Rhine. It formed the mouth of a deep fissure in a current of basalt derived from an ancient volcanic cone above it, and its floor was covered with a crust of ice at the time of his visit, about noon on a very hot day in August.

The phenomenon of wind-grottoes is analogous to that of ice-caves, and not seldom associated with it. Here cold currents of air, increasing in violence as the day is hotter, are found to blow from the interstices of rocks. One of the most celebrated of these Æolian caverns is found near Terni in Italy. The entrance is closed by an old gate, through the crevices of which the wind issues with a rustling noise, while in the grotto itself the current is sufficiently strong to extinguish a torch. The proprietors of some neighbouring villas have put the phenomenon to an ingenious use. Leaden pipes, branching out from the grotto, convey on sultry summer days an agreeable coolness through masks of gypsum with wide distended mouths, which are fixed in the walls of the apartments.

The small town of Roquefort in France has been renowned ever since the time of the Romans for the delicious flavour of its cheese, which is said to owe its excellence to the cool cellars in which it is matured. These are excavated on the northern slope of a great chalk plateau, and communicate with numerous fissures in the rock, from which air-currents stream forth of so low a temperature as to cause a thermometer marking +23° R. in the shade, and in the external atmosphere, to fall to +4° R. when exposed to their influence. The cellars are so valuable that one, which cost 12,000 francs in construction, sold for 215,000 francs.

In times of ignorance, superstition could not fail to attach its fables to the phenomenon of wind-grottoes. A cave near Eisenach was supposed to be the seat of purgatory, and popular credulity or terror willingly transformed the sounds produced by the rushing air-currents into the wailings of tormented souls.

Fortunately, modern science affords us a more satisfactory explanation of the phenomenon. Pictet represents the case of a cave with cold currents of air to be much the same as that of a mine with a vertical shaft ending in a horizontal gallery, of which one extremity is in communication with the open air, at a point much lower, of course, than the upper extremity of the shaft. The cave or wind-hole corresponds to the horizontal gallery, and the various fissures in the rock take the place of the vertical shaft, and communicate freely with the external air. In summer the columns of air contained in these fissures assume nearly the temperature of the rock in which they rest—that is to say, the mean temperature of the district; and therefore they are heavier than the corresponding external columns of air which terminate at the mouth of the cave. The consequence is, that the heavy cool air descends from the fissures, and streams out into the cave, appearing as a cold current, and the hotter the day—that is, the lighter the columns of external air—the more violent will be the disturbance of equilibrium, and therefore the more palpable the current.

The evaporation which takes place as the air-currents descend through the moist rock-fissures likewise tends to lower their temperature. Several naturalists have attempted to explain the phenomena of ice-caves in a similar manner, as being produced by cold currents still further refrigerated by the evaporation caused in the moist and porous rocks through which they pass. But to this theory there are weighty objections, as in many ice-caves there is no current whatever, and in all the cases of cold air streams investigated or mentioned by De Saussure, the lowest temperatures observed were still considerably above the freezing-point, and consequently incapable of converting water into ice.

Mr. Browne believes that, in many cases, the phenomenon may be satisfactorily accounted for by the position and surroundings of the caves in which it occurs; though, no doubt, cold currents and evaporation may often have an influence in maintaining the low temperature of ice-caves.

In every one of the fourteen natural glaciÈres which he visited, the level at which the ice was found was considerably below the level at the entrance of the cave; so that, on ordinary principles of gravitation, the heavy cold air within could not be dislodged by the lighter warm summer air without. Heat naturally spreads very slowly in a cave like this; and even when some amount of heat does reach the ice, the latter melts but slowly, for ice absorbs 60° C. in melting; and thus when ice is once formed, it becomes a material guarantee for the permanence of cold in the cave.

Another means for preventing the encroachments of the hotter seasons is the dense covering of trees and shrubs, which, in the case of many of the glaciÈres, shields their entrance or their roof from the rays of the sun, and thus keeps off the effects of direct radiation. Mr. Browne found all the glaciÈres that came under his observation thus protected, with the single exception of that of St. Georges, where, in consequence of an incautious felling of wood immediately near the mouth, trunks of trees had been laid horizontally over it, to prevent the rays of the sun from striking down on to the ice. He moreover invariably found that the entrances to the caves were more or less sheltered against all winds—a very important condition, as air-currents from without would infallibly bring in heated air, in spite of the specific weight of the cold air stored within. There can be no doubt, too, that the large surfaces which are available for evaporation have much to do with maintaining a somewhat lower temperature than the mean temperature of the place where the cave occurs. Another great advantage which some glaciÈres possess must be borne in mind, namely, the collection of snow at the bottom of the pit in which the entrance lies. This snow absorbs, in the course of melting, all the heat which strikes down by radiation, or is driven down by accidental turns of the wind; and the snow water thus forced into the cave will, at any rate, not seriously injure the ice.

It is easy to understand how, in caves thus protected against the influence of summer heat, a great part of the ice accumulated during the winter may be preserved, and that, for an explanation of the phenomenon, it is by no means necessary to have recourse to cold blasts descending from the interior of the rock in which they are situated. It is indeed a common belief that the ice-caves are colder in summer than in winter, and consequently contain a greater abundance of ice during the former season; but this belief may well be considered as one of those popular fallacies, which—though, by dint of repetition, they come to be common articles of faith—have in fact no substantial proofs to support them.