CHAPTER XVI.

BRIEF NOTICES OF OTHER ICE-CAVES.

On the Brandstein in Styria, in the district of Gems, there is an ice-hole closely resembling some of the glacières of the Jura. It is described by Sartori,[[123]] as lying in a much-fissured region, reached after four hours of steep ascent from the neighbouring village, through a forest of fir. Some of the fissures contain water and some snow, while others are apparently unfathomable. From one of the largest of these, a strong and cold current blows in summer, and in this fissure is the ice-hole. Sartori 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 farther 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 termination of this hole, and the stones which they rolled down into it seemed to go on for ever. The greatest height of the cave is about 36 feet, and its length 192 feet, with a maximum breadth of 126 feet. Towards the end of autumn, the temperature of the ice-hole rises so much, that the glacial decorations disappear, and various wild animals are driven by the cold of winter to take shelter in the comparative warmth of the cave. The elevation of the district in which this ice-hole occurs is about 1,800 German feet above the sea.

In Upper Styria, where the Frauenmauer overlooks the basin in which the mining town of Eisenerz is situated, an ice-cave has been explored, and a description of it has been given by certain members of the Austrian Alpine Club.[[124]] The Brandstein is spoken of as one of the peaks in the immediate neighbourhood; and as the cave previously described is stated by Sartori to be on the Brandstein, that district would seem to be rich in glacières. The cavern is most easily explored from Eisenerz, and on that side the entrance is 4,539 Vienna feet above the sea. Its other outlet, in the Tragöss valley, is 300 feet higher. The total length of the cave is 2,040 Vienna feet. After passing the entrance, which is an archway from 12 to 18 feet high, the main course of the cave is soon left, and a branch is followed which leads to the Eis-kammer. This ice-chamber consists of a grotto from 30 to 40 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 the game of Eisschiessen, so popular in Upper Styria as a winter diversion. The hotter the summer, the more ice is found in the Eiskammer, and the general belief is that it all disappears in winter.

The cave proper, which assumes stupendous dimensions in its long course, shows no ice. It seems to be formed in the Muschelkalk of the Trias formation, and so far no limestone stalactites have been discovered. It has not, however, as yet been fully explored. The editor of the proceedings of the Austrian Alpine Club gives a reference to Scheiner, 'Ausflug nach der Höhle der Frauenmauer,' (Steiermarkische Zeitschrift, neue Folge, i. 2, 1834, p. 3.)

At Latzenberg, near Weissenstein in Carniola, there is another ice-cave, described by Rosenmüller.[[125]] It is entered by a long dark passage in which are pillars of ice arranged like the pipes of an organ, varying from the thickness of a man's body to the size of a straw. All these are said to melt in winter. Farther on are two other passages, one of which passes upwards over Stufe, and is coated in summer with ice; the other has not been explored.

Near Glaneck in the Untersberg, not far from Salzburg, is a cave called the Kolowrathöhle, of which a description is given by Gümbel in his great geological work on the Bavarian Alps.[[126]] It is a spacious cavern, opening in a steep wall of rock above the Rositenschlucht between the Platten and Dachstein-kalk.[[127]] An ice-current rushes from within, and ice is found on the threshold, becoming more prevalent in the farther recesses of the cave. The lower parts are tolerably roomy, and masses of ice of various shapes are found piled one upon another, lighting up with magical effect when torches are brought to bear upon them. Gümbel believes that the cold currents which stream into the cave from the numerous fissures in its walls are the cause of the ice; and though this is the only known ice-cave far and near, he imagines that the icy-currents which are frequently met with in that district, and in the Hochgebirge, would be found to proceed in reality from like caves, if the fissures from which they blow could be penetrated.

Behrens[[128]] describes two ice-caves near Questenberg, in the county of Stollberg, on the Harz mountains. They both occur in limestone, and are known as the Great and Little Ice-holes. The one is close to the village of Questenberg, and consists of a chasm several fathoms deep, so cold that in summer the water trickling down its edges is frozen into long icicles. The opening is large and faces due south, and yet the hotter the day the more ice is found; whereas in winter a warm steam comes out, as if from a stove. The other cave is farther into the mountain; it is spacious and light, and very cold in summer.

In Gehler's Physik. Wörterbuch (Art Höhle), a small hole is mentioned near Dôle, which is said to be remarkable for the large and curiously-shaped icicles found there; but no sufficient account of it seems to have been given.

An ice-hole is also spoken of in the same article, which occurs on the east side of the town of Vesoul.[[129]] The hole is described as being small, with a little rivulet of water: this water, and also that which trickles down the walls of the cave, is converted into ice, and so much is formed on a cold day that it requires eight warm days to melt it. Gollut, in his description of the fré-puits of Vesoul,[[130]] observes that the remarkable pit known by that name was so cold, that in his time it had never been fully explored. Gehler's expression, however, 'a small hole,' cannot possibly apply to the fré-puits; so that these would seem to be two different examples of cold caves near Vesoul.

There is an interesting account in Poggendorff's Annalen[[131]] of a visit made by Professor A. Pleischl to a mountain in the circle of Leitmeritz, where ice is found in summer under very curious circumstances. The mountain is called Pleschiwetz, and lies above Kameik, in Bohemia, not far from the town of Leitmeritz. On the 24th of June in each year, large numbers of pilgrims assemble at the romantic chapel of S. John the Baptist in the Wilderness; and it is a part of their occupation to search for ice under the basaltic rocks, and carry it home wrapped in moss, as a proof that they have really made the pilgrimage. Professor Pleischl visited this district at the end of May 1834. The weather was hot for the season, as had been the case in April also, and there had been very little snow in the winter. A path leads from the chapel of S. John through the woods which deck the Pleschiwetz, and then over a small plain to the foot of the basaltic rocks. Here the mountain slopes away very steeply to the south, and the slope is thickly strewn with basaltic débris. From east to west this slope measures about 40 fathoms, and its length is about 70 fathoms. It is surrounded on both sides and at the foot by trees and shrubs. The sun burned so directly on to the débris, that the basaltic blocks were in some cases too hot to be touched by the naked hand.

Professor Pleischl spent three hours of the early afternoon on this spot. The upper surface of the basaltic blocks had a temperature of at least 122° F. The presence of an icy current was detected by inserting the hand into the lower crevices; and on removing the loose stones to a depth of 1-1/2 or 2 feet, ice was found in considerable quantities. On the 27th of August, he proceeded to make a further investigation of this phenomenon; but he found the temperature of the blocks only 106° F., and in the crevices, at a depth of 2 or 3 feet, the lowest temperature reached was 38°·75 F. The external temperature in the shade was at the same time 83° F.

A third visit, in January 1835, gave no results; but on January 21, 1838, the Professor succeeded in determining some very remarkable facts. A depression in the sloping plain is called, par excellence, the ice-hole; and this is surrounded by firs and birches, which grow within three or four fathoms of the edge of the hole, so that the rays of the sun do not reach the hole in winter. Fresh snow lay on these trees; and there was nowhere any sign of melted snow, or of the formation of icicles. The basaltic débris, in which ice had been found in the summer, covers here a space of 5 fathoms long by 3 or 4 broad, immediately at the foot of a steep basaltic precipice. At eleven in the morning the temperature was 14° F. in the shade; and snow lay all round the ice-hole, to a thickness of 1-1/2 or 2 feet. The snow which covered the débris was pierced by holes, which could not have been caused by the sun, for its rays did not penetrate the trees; and, indeed, no sun had been visible for some days. These holes were generally turned towards the north, and were like chimneys. On investigation, it was found that icicles hung down into them, showing, of course, past or present thaw, and within the cavities no ice was found. The thermometer gave here from 27°·5 F. to 25°·15 F.; but in the crevices, into which the thermometer could not be pushed, the hand discovered a warm air. The moss drawn from these crevices was found to be steeped in unfrozen water, and it froze promptly when brought into the outer air.

The party afterwards climbed up the precipitous basalt, and reached, at 3 P.M., a level covered with large blocks of the same material, where the thermometer was slightly under 12° F. in the shade. The blocks were for the most part stripped of snow, and in some cases thin shields of ice were observed standing out two or three inches from them, forming hollow chambers, in which an agreeable warmth was found. These shields were invariably on the south side of the stones, the north side being free from ice and snow alike. In some places vapours were seen to rise. The thermometer gave 41° F. at a depth of six inches among the stones, though the external temperature, as has been said, was 12° F. For eight days previously, the thermometer had been always far below the freezing point, and on the 17th (four days before) had been 13° below zero (F.). On the 19th and 20th heavy snow had fallen. All these facts seem to show that the warmth which had caused the chimneys in the snow over the ice-holes, and the heated vapours on the higher parts of the mountains, proceeded from within, and not from without.

The people of the district assured Professor Pleischl that the hotter the summer, the more ice is formed; and that it disappears when the nights become long and the days short. Dr. Weiss, for six years head of the Gymnasium of Leitmeritz, stated that when one of the holes was emptied of ice in the summer, it filled again in a few days. The explanation given by the Professor of this phenomenon is, that the blocks of basalt, that being an excellent conductor of heat, pass so much warmth through to their under surfaces--which form the roof of small chambers filled with a spongy mass of decaying leaves--that the rapid evaporation thereby caused produces the cold air and the ice. He omits to explain why there should be anything exceptional in the winter phenomenon of the crevices among the stones.

There are two other places in Bohemia where ice is found in summer. One is on the Steinberg, in the county of Konaged;[[132]] it is a small basin, surrounded by trees, where, in the middle of summer, lumps of ice are found under basaltic débris. This ice is only formed, according to Sommer, in the hottest part of the year. The other is on the Zinkenstein, one of the highest points of the Vierzehnberg, in the circle of Leitmeritz. It is described by Sommer[[133]] as a cleft, five fathoms deep, in the basaltic rock, where ice is found in the hottest seasons. Professor Pleischl put this assertion to the test by visiting the spot in the end of August, when he found no signs of ice.

Another writer in Poggendorff[[134]] describes a somewhat similar appearance on the Saalberg. Here ice is found on the surface from June to the middle of August; and that, too, with a west exposure and in moderate shade. In July, the ice was so abundant that it could be seen from some distance: it was half a foot thick, and yielded neither to sun nor rain. In the middle of August there was no ice on the surface; but when the loose débris was removed, the most beautiful ice appeared, and at a little depth all was frozen as hard as if it had been the depth of winter.[[135]] The people who work in the neighbourhood declare that the place remains open, and free from ice or snow, in the greatest cold, and that no ice begins to form till the month of June. When the writer of the account in Poggendorff visited the ice-hole, the peasants were in the habit of carrying large masses of ice down to their houses, through a temperature of 81° F.

Reich[[136]] gives a detailed and valuable account of the prevalence of subterranean ice on the Sauberg, a hill which forms one side of a ravine near Ehrenfriedersdorf. The surface is about 2,000 feet above the sea, and its mean temperature, as determined by many careful observations, about 45° F. There are several tin-mines in this district, and the extended observations made by the authorities establish the curious fact that the mean temperature is considerably lower beneath than at the surface. For instance, in the S. Christoph pit, it is found that the mean temperature, at 15 fathoms below the surface, is only slightly above 42° F.; while at the Morgenröther cross-cut the same mean temperature is found at a depth of 46 fathoms. The annual change of temperature is very small in these mines, and the maximum and minimum are reached very late; so that, if a point could be found with a mean temperature of 32° F., ice would increase there up to June or even July, and then diminish until December or January; in which case the phenomenon so often said to be observed in connection with subterranean ice--the melting in winter and forming in summer--would really be presented.

The ice on the Sauberg is frequently found to commence at a depth of 3 or 4 fathoms, and in the years 1811 and 1813 it extended to 24 fathoms below the surface: this depth, however, was exceptionally great, and as a rule the limit is reached at about 14 fathoms.[[137]] The ice is usually not very firm, and can be broken by stout blows with a stick; but between the years 1790 and 1800, when it was found at a depth of from 3 to 9 fathoms, it was so hard that blasting became necessary, and at that time the miners were with difficulty protected from the effects of the severe cold. The greatest quantity of ice is found in the interstices of the rubbish-beds of old workings, and here it assumes a crystalline form, the rocks being covered with a 'fibrous' structure, arranged perpendicularly to their surface.

Reich reports the universal presence of cold currents of air in these shafts and mines, and, in consequence, takes the opportunity of contradicting a statement in Horner's Physik. Wörterbuch,[[138]] that the absence of all current of air is essential to the formation of subterranean ice. He quotes the case of the cheese-caves of Roquefort as a further confirmation of his own observations with regard to the connection between ice in caves and cold currents of air; but of the many accounts which I have met with of the curious caves referred to, both in books and from the lips of those who have visited them, not one has made any mention of ice.[[139]] He states, too, that when the strength of the current is diminished, its temperature is increased; a fact which all observations of the cold currents in caves, especially those made with so much care by M. Saussure, abundantly establish.

In the way of explanation, Reich mentions the possibility of rocks of peculiar formation possessing actually a low degree of temperature;[[140]] but he rejects this suggestion, preferring to believe that in some cases the cold resulting from evaporation is the cause of ice, and in others the greater specific gravity of cold as compared with warmer air.

In the Bulletin des Sciences Naturelles,[[141]] it is stated that a large quantity of ice is found in one of the recesses of the grotto of Antiparos--a fact which I have not seen mentioned elsewhere. After penetrating a long way through difficult fissures, a square chamber is at length reached, measuring 300 feet in length and breadth, with a height of about 80 feet. The walls and roof and floor are beautifully decorated with ice, and reflect all the colours of the rainbow. There are groups of pyramidal and round columns, and in some parts of the cave screens or curtains of ice 10 or 12 feet broad hang down to the floor.

In a later volume of the same periodical,[[142]] there is a description of a hill in Virginia where ice is found in summer. This hill lies near the road between Winchester and Romney, on the North River, latitude 39º N. One side of the hill is entirely composed of loose stones from ten to twenty pounds in weight, and under these the ice is found, although their upper surface is exposed to the full sun from 9 or 10 A.M. till sunset. In all seasons there is an abundance of ice. A writer in the 'London and Paris Observer'[[143]] visited the spot on the 4th of July, after a time of stifling heat, and in ten minutes he found more ice than the whole party could have carried away. He did not explore any farther than the foot of the hill; but the neighbours, who used the ice regularly in summer, assured him that it was to be found high up also. A constant and strong current issued from the crevices, stronger and infinitely colder than the current in the famous 'blowing cave' of Virginia. A man had built a store-room for meat within the influence of one of these currents, and hard dry icicles were seen hanging from the wooden supports inside: the flies, too, which had been attracted by the meat, were found frozen on to the stones. This is not the only district where ice is found within temperate latitudes in North America. In Professor Silliman's 'American Journal of Science,'[[144]] in a sketch of the geology of the township of Salisbury, Con. (latitude 43° N.), 'natural ice-houses' are mentioned. These consist of chasms of considerable extent in the mica-state, where ice and snow remain during the greater part of the year. The principal of these chasms lies in the east part of the town, and is several hundred feet long, sixty feet deep, and about forty wide. The slate is of a very compact kind; and the walls are perpendicular, and correspond with much exactness. At the bottom is a cold spring, and a cave of considerable extent, in which it is probable that the ice lies--for the writer does not specify the position in which it is found. The chasm is a favourite retreat in summer, and is called the Wolf-hollow, from its having formerly been a famous haunt for wolves.

Similar receptacles for summer-ice are found in several places in North America. In the forty-ninth volume of the Sitzungsberichte der Kaiserl. Akademie in Wien (1te. Abth.), a list of references to various ice-holes is appended to a paper by Dr. Boué on the geology of Servia. Many of the passages referred to have nothing to do with ice-caves, as, for instance, the sections of De Saussure's book describing his observations of 'cold caves', or the account of the mass of ice and snow from which the river Jumna springs, for which Dr. Boué refers to the 'Philosophical Magazine' for November 1823, meaning, in fact, the 'London Magazine'. The 'Description des Glacières' of M. Bourrit is also given as a part of the literature on ice-caves; whereas (see the account of the Glacière of Montarquis, in the Valley of Reposoir) by 'glacière' M. Bourrit meant only a locality where ice is to be found, or a glacier district. Dr. Boué, however, gives some references to the 'American Journal of Science' which it is possible to make out by a careful search in the neighbourhood of the volume and page he mentions. In vol. iv. (1822,--Dr. Boué says 1821) there is an account by the editor[[145]] of a natural ice-house in the township of Meriden, Con., between Hartford and Newhaven, at an elevation of not more than 200 feet above the level of the sea. The ice is found in a narrow defile, which is hemmed in by perpendicular sides of trap-rock, and displays a perfect chaos of fallen blocks of stone. The defile is so narrow, that the sun's rays only reach it for an hour in the course of the day; and even the trees and rocks, and beds of leaves, protect the ice from any very material damage. Dr. Silliman visited this defile on the 23rd July, 1821,[[146]] with Dr. Isaac Hough, the keeper of a neighbouring inn, and found that the ice was only partially visible, in consequence of the large collection of leaves which lay on it: they sent a boy down with a hatchet, and he brought up some large firm masses, one of which, weighing several pounds, they carried twenty miles to Newhaven, where it did not entirely disappear till the morning of the third day. Seven miles from Newhaven, in the township of Branford, there is a similar collection of ice. In both of these cases, the ice is mixed with a considerable quantity of leaves and dirt.

In the same volume (p. 331,--Dr. Boué says p. 33), two accounts are given of a natural ice-house near the summit of a hill in the neighbourhood of Williamstown (Mass.). In the next volume there is a further account of it by Professor Dewey, stating that since the trees in the neighbourhood had been cut, the snow and ice had disappeared each year about the first of August.

In vol. xlvi. (p. 331) an ice mountain in Wallingford, Rutland County (Vt.), is described, which is ordinarily known in the neighbourhood as the ice-bed. An area of thirty or fifty acres of ground is covered with massive débris of grey quartz from the mountains which overhang it; and here--especially in a deep ravine into which many of the falling blocks of stone have penetrated--ice is found in large quantities. It appears to be formed during the melting of the snow in February, March, and April, and vanishes in the course of the summer, in hot years as early as the last days of June.

These descriptions call to mind the Glacière of Arc-sous-Cicon, in which many of the features of the American ice-caves are reproduced. An American photograph is current in this country, in the form of a stereoscopic slide, representing an ice-cave in the White Mountains, New Hampshire; but it is only a winter cave, and in no way resembles any of the glacières I have seen. It is merely a collection of long and slender icicles, with beds of ice formed upon stones and trunks of trees on the ground; nothing more, in fact, than is to be seen in any tolerably severe winter in the neighbourhood of a cascade in a sheltered Scotch burn.

The 'American Journal of Science' (xxxvi. 184) gives a curious instance of a freezing-well near the village of Owego, three-quarters of a mile from the Susquehanna river. The depth of the well is 77 feet, and for four or five months in the year the surface of the water is frozen so hard as to render the well useless. Large masses of ice have been found in it late in July. A thermometer, which stood at 68° in the sun, fell to 30° in fifteen minutes at the bottom of the well; and the men who made the well were forced to put on thick clothing in June, and even so could not work for more than two hours at a time. No other well in that neighbourhood presents the same phenomenon. A lighted candle was let down, and the flame became agitated and thrown in one direction at a depth of 30 feet, but was quite still at the bottom; where, however, it soon died out. The water is hard or limestone water.

Rocks of volcanic formation would seem to afford favourable opportunities for the formation of ice. Scrope mentions this fact in an account of the curious district called Eiffel or Eifel, in Rhenish Prussia, which was published originally in the 'Edinburgh Journal of Science,'[[147]] and has since been translated in Keferstein's Deutschland.[[148]] The village of Roth, near Andernach, is built on a current of basalt, derived from the cone above it, which has at some time sent down a stream of lava to the north and west. A small cavern near the village, forming the mouth of a deep fissure in the lava-stream, half-way up the cone, displays a phenomenon which the writer says he has often observed in volcanic formations. The floor of the cavern was covered with a crust of ice at the time of his visit, about noon on a very hot day in August. The peasants report that there is always ice in summer, and never in winter, when the sheep retreat to the cave on account of its warmth. Steininger[[149]] found a thickness of 3 feet of ice on September 19, 1818, but it was evidently in a melting state, and the thermometer stood at 36·5 F. in the cavern. He describes it as possessing a narrow entrance facing north, entirely sheltered from the sun by lava-rocks, and by the trees of a wood which covers the cone of scoria.

Scrope believes that this is the mouth of one of the arched galleries so frequently met with under lava in Iceland, Bourbon, and elsewhere; and on this he founds his explanation of the phenomenon. If the other extremity is connected with the external air at a much lower level, a current of air must be constantly driven up this gallery, and in its passage will be dried by the absorbent nature of the rock--which is perhaps partly owing to the sulphuric or muriatic acid it contains[[150]]--- and the evaporation caused by this current produces a coating of ice on the floor of the grotto, where there is a superficial rill of water. The more rarified the lower external air, the more rapid will be the current of cool air; and, therefore, the greater the evaporation. The winter phenomenon is to be explained by the fact that the current of air will be about the mean annual temperature of the district, taking its temperature, in fact, from the rocks through which it passes; and, therefore, by contrast the grotto will appear warm.

The same writer mentions a similar example of summer ice in Auvergne.[[151]] There is a natural grotto in the basalt near Pont Gibaud, some miles to the north-west of Clermont, in which a small spring is found partly frozen during the greatest heats of summer, while the water is said to be warm in winter; probably, Scrope observes, only seeming to be warm by contrast with the external temperature. The water is apparently frozen by means of the powerful evaporation produced by a current of very dry air proceeding from some long fissures or arched galleries which communicate with the cave. In this case also the writer suggests that the air owes its dryness to the absorbent qualities of the lava through which it passes: he repeats, too, the remark that the phenomenon is of common occurrence in caverns in volcanic districts.[[152]]

There is a remarkable instance of ice occurring under lava, near the Casa Inglese on Mount Etna, which it may be as well to mention, though the causes of its existence have probably nothing in common with the phenomena of ice-caves, or summer ice. An account of it is to be found in Sir Charles Lyell's 'Elements of Geology.'[[153]] It appears that the summer and autumn of 1828 were so hot, that the artificial ice-houses of Catania and the adjoining parts of Sicily failed. Signer M. Gemmellaro had long believed that a small mass of perennial ice at the foot of the highest cone of Etna was only a part of a large and continuous glacier covered by a lava current, and from this he expected to derive an abundant supply of ice. He procured a large body of workmen, and quarried into the ice; but though he thus proved the superposition of lava for several hundred yards, the ice was so hard, and the expense of quarrying consequently so great, that the works were abandoned. This was on the south-east of the cone, not far from the Casa Inglese. Sir Charles Lyell suggests that, probably, at the commencement of some eruption, a large mass of snow has been thickly covered with volcanic sand, showered upon it before the arrival of the lava itself. This sand is a non-conductor of heat, and would therefore tend to preserve the snow from complete fusion when the hot lava-stream passed over it, and thus the existence of the underground glacier may be explained. The peasants of the district are so well acquainted with the non-conducting properties of volcanic sand, that they secure an annual store of snow, for providing water in summer, by strewing a layer of sand a few inches thick upon a field of snow, thus effectually shutting out the heat of the sun. It is curious that when De Saussure visited Chamouni for the first time, his attention was arrested by the sight of women sowing what seemed to be grain of some kind in the snow; but, on enquiring, he found that it was only black earth, which the inhabitants spread on the snow in spring, in order to make it disappear sooner. He was told that snow thus treated would melt a fortnight or three weeks before the ordinary time for its disappearance in the valley; but it will be seen that this does not contradict the theory of the Sicilian peasants.[[154]]

Sir Charles Lyell adds that, after what he saw on Mount Etna, he should not be surprised to find layers of glacier and lava alternating in some parts of Iceland.

Something similar was observed by Von Kotzebue, near the sound which bears his name.[[155]] His party was encamped on a large plain covered with moss and grass, when they discovered a fissure which revealed the fact that the moss and grass were but a thin coating on a layer of ice a hundred feet thick. This was not mere frozen ground, but aboriginal ice; for, in the ice which formed the walls of the fissure, they found the bones and teeth of mammoths embedded.

The frozen soil of Jakutsk, in Siberia, has for many years attracted considerable attention. The ordinary law of increase of temperature in descending below the surface of the earth would appear, however, to be only modified here; for it is found in sinking a well which has afforded opportunities for observing the state of the soil, that the temperature gradually increases with the depth.[[156]]

Two ice-caverns were examined by Georgi, in the course of his travels in Russia.[[157]] One occurs near the mines of Lurgikan, on the east side of a hill about 450 feet high, not far from the confluence of the Lurgikan stream with the Schilka (a tributary of the Amur), in the province of Nertschinsk. In the course of driving an adit in one of the lead-mines, in the year 1770, the workmen were struck by the hollow sound given forth by the rock, and, on investigation, they found an immense grotto or fissure, of which the entrance was so much blocked up by ice that they had much difficulty in sliding down by means of ropes. The fissure extended under the hill, in a direction from north to south, and was 130 fathoms long, from 1 to 8 broad, and from 3 to 12 high. Where it approached nearest the surface, the thickness of the roof was about 10 fathoms. The rock is described by Georgi as quarzig, bräunlich, und von einem starken Kalkschuss. He found the greater part of the walls covered with ice, and many pillars and pyramids of ice on the floor. The cold was moderate, and was said to be much the same in summer and winter. Patrin has given a fuller description of the same cavern in the Journalde Physique.[[158]] The lead-mine is in limestone rock, containing a third part of clay. The entrance to the glacière was still difficult at the time of his visit, and it was necessary to use a rope, and also to cut steps, for the descent was made along a ridge of ice with almost perpendicular sides. The spectacle presented by the decoration of the roof was remarkably beautiful, long festoons and tufts of ice hanging down, light and brilliant as silver gauze: this ice was supposed to be formed from the abundant vapours of the beginning of winter, and resembled glass blown to the utmost tenuity. It was crystallised, too, in a wonderful manner. Patrin found long bundles of hexahedral tubes, the walls of which were formed of transverse needles: the diameter of these tubes was from two to six lines only, but at the lower extremities they opened out into hollow six-sided pyramids, more than an inch in diameter, so that the festoons, sometimes as large round as a man, presented terminal tufts of some feet in diameter, which glittered like diamonds under the influence of the torches. Towards the farther end of the fissure, stalactites of solid ice were found, displaying all the forms and more than all the beauty of limestone stalactites. The other instance mentioned by Georgi occurred in the mines of Serentvi, where two of the levels yielded perennial ice, and were thence (Georgi says) called Ledenoi. A spring of water flowed from the rock at a depth of thirty fathoms below the surface, and was promptly frozen into a coating of ice a foot thick. Patrin[[159]] visited Serentvi, but he did not observe any ice in the mines. He believed the rock to be very ancient lava.

Reich[[160]] mentions a cavern on Mount Sorano which contains ice, quoting Kircher;[[161]] but he seems to have misinterpreted his author's Latin.[[162]] He also refers to the existence of ice in the mines of Herrengrund in Hungary, and Dannemora in Sweden. Kircher, who has the credit of having been the first to call attention to the increase of temperature in the earth, made full enquiries into the temperature of the mines at Herrengrund, but he was not informed of the existence of ice.[[163]] Townson visited these mines in the course of his travels in Hungary, and neither does he make any mention of ice in connection with them. He describes them as lying south of Teplitz, in a limestone district, with sandstone in the more immediate neighbourhood. The mines themselves (copper mines) are in a kind of mica-schist, which the people call granite. The superintendent of mines informed Reich that one of the shafts is called the ice-mine, from the fact that when the workmen attempted to drive a gallery from south to north, they came upon ice filling up the interstices of the Haldenstein, within five fathoms of the commencement of the gallery. The temperature was so low, and the expense caused by the frozen mass so great, that the working was stopped.

The iron mines of Dannemora, eleven leagues from Upsal, contain a large quantity of ice, according to a manuscript account by Mr. Over-assessor-of-the-board-of-mines Winkler:[[164]] Jars, however, in his Voyages Métallurgiques,[[165]] gives a full description of them without mentioning the existence of ice. He states that ice is found in the mines of Nordmarck, three leagues from Philipstadt in Wermeland, a province of Sweden: these mines are merely numerous shafts sunk in the earth, reaching to the bottom of the vein of ore, so that they are fully exposed to the light, and yet the walls of the shafts become covered with ice at the end of winter, which remains there till the middle of September. Jars believed that, if it were not for the heat caused by blasting, and by the presence of the workmen, the ice would be perennial. Humboldt[[166]] speaks of the ice in these mines and on the Sauberg. Reich states that ice is found in the mill-stone quarry of Nieder-Mendig, quoting Karsten's Archiv für Bergbau.[[167]] The ice is found in the hottest days of summer, although the interior of the quarry is connected with the outer air by many side shafts. The porous nature of the stone is assigned as the cause of the phenomenon. Daubeny (On Volcanoes) describes the remarkable basaltic deposits at Niedermennig--as he spells it--but says nothing of the existence of ice.

Daubuisson[[168]] speaks of a Schneegrube, on a summit of the Riesengebirge, in Silesia, 4,000 feet above the sea; but such holes are common enough at that elevation, and I have seen two or three remarkable instances on the Jura, within the compass of one day's walk. Voigt[[169]] describes an Eisgrube in the Rhöngebirge, on the Ringmauer, the highest point of the Tagstein, where abundant ice is found in summer under irregular masses of columnar basalt. Reich had received from a forest-inspector an account of an ice-hole in this neighbourhood, called Umpfen, which is apparently not the same as that mentioned by Voigt.

In the Saxon Erzgebirge there are three points remarkable for their low temperature,[[170]] in addition to the mines on the Sauberg mentioned above. These are the Heinrichssohle, in the Stockwerk at Altenberg, where the mean of two years' observations gives the temperature 0°·54 F. lower at a depth of 400 feet than at the surface; the adit of Henneberg, on the Ingelbach, near Johanngeorgenstadt, where the temperature was again 0°·54 F. lower than in shafts some hundred feet higher; and the Weiss Adler adit, on the left declivity of the valley of the Schwarzwasser, above the Antonshütte. It would appear that there are local causes which affect the temperature in the Erzgebirge, for Reich found that in several places the mean temperature of the soil was higher than that of the air: for instance--

Soil.AirHeight above the sea.
Altenberg...42·732° Fahr.41·27°2,450 feet
Markus Röhling...43·542° "41·832°1,870 "
Johanngeorgenstadt....43·115° "41·09°2,460 "

The temperature at Markus Röhling is peculiarly anomalous, considering the elevation of the surface above the sea.

There is said to be an ice-cave in Nassau, but I have been unable to obtain any account of it, unless it be the same as the ice-field mentioned on page 303.

There is a cave in the south-east of Hungary[[171]] which presents the same features as several of the glacières I have visited. It is called the Ice-hole of Scherisciora, and is described as lying in the Jura-kalk, at a distance of 2-1/2 hours north-east from the forest-house of Distidiul. The approach is by ladders, down a pit 30 fathoms wide and 24 deep; and when the bottom of this pit is reached, an entrance is found to the cave in the north wall, in the neighbourhood of which is congealed snow which shortly becomes ice. The floor of the first chamber is composed of glacier-ice, separated from the side walls by a cleft from 1 to 3 feet wide, where it shows a depth of from 4 to 6 feet; it is as smooth as glass, and about 6 fathoms from the entrance a cone of ice stands upon it, 8 or 9 feet high. Both the floor and the cone are at once seen to be transformed remains of ancient masses of snow, and are of a dirty yellow colour.

At the back of this chamber, a narrow passage opens towards the interior of the mountain, and winds steeply down with a height of 4 feet, and a length of a few fathoms, till a magnificent dome is reached, on the beauties of which Herr Peters becomes eloquent. The floor is so smooth that crimpons are necessary, and stalagmites and stalactites of ice are found in rich profusion, the latter being generally formed on small limestone stalactites, while the former have no such nucleus.

There is another opening near the original entrance to the cave, a sort of fissure covered with elegant forms of ice, leading to a steep shaft. The imperial forester of Topfanalva was bold enough to let himself down the slope of ice which formed the edge of the shaft, on a rope ladder 60 feet long, notwithstanding the difficulty of grasping the iron steps which of course lay pressed on to the ice; but when he had descended about 30 feet, the shaft became perpendicular, and stones thrown in showed a very considerable depth. There appeared to be no sound of water in the abyss below.

Both entrances, that to the shaft as well as that to the second chamber, were ornamented with delicate ice crystals, which occurred both on the limestone stalactites and on the walls, and presented almost the appearance of plants of cauliflower. The ice-floor of the first chamber is described as consisting of a 'coarse-grained' material.

In the south-east of Servia, on the western slope of Mount Rtagn, is a pit 20 feet in diameter, and 40 or 50 feet deep, the bottom of which is reached by a succession of trunks of trees with the branches lopped off, a sort of ladder called stouba by the natives.[[172]] The peasants assert that the snow and ice disappear from this pit in September, and do not reappear before June. The Swiss peasants have never yet got so far as to say that the snow in their pits disappears in winter and returns in summer. Boué[[173]] found the temperature of the bottom of the pit to be 28°·4 F., while that of the air outside was 76° F. The same writer[[174]] mentions a source in a mill-stone quarry in Bosnia which is frozen till the end of June.