Many of the pa.s.sages 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 ma.s.s of ice and snow from which the river Jumna springs, for which Dr. Boue refers to the 'Philosophical Magazine' for November 1823, meaning, in fact, the 'London Magazine'. The 'Description des Glacieres' of M. Bourrit is also given as a part of the literature on ice-caves; whereas (see the account of the Glaciere of Montarquis, in the Valley of Reposoir) by 'glaciere'

M. Bourrit meant only a locality where ice is to be found, or a glacier district. Dr. Boue, 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. Boue 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 ma.s.ses, 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 quant.i.ty of leaves and dirt.

In the same volume (p. 331,--Dr. Boue says p. 33), two accounts are given of a natural ice-house near the summit of a hill in the neighbourhood of Williamstown (Ma.s.s.). 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 ma.s.sive _debris_ 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 quant.i.ties. 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 Glaciere 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 glacieres 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' (x.x.xvi. 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 ma.s.ses 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 365 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 pa.s.sage 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 pa.s.ses; 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 pa.s.ses: 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 ma.s.s 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 ma.s.s 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 pa.s.sed 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 gra.s.s, when they discovered a fissure which revealed the fact that the moss and gra.s.s 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, braunlich, 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 glaciere 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 gla.s.s 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, stalact.i.tes of solid ice were found, displaying all the forms and more than all the beauty of limestone stalact.i.tes. 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 ma.s.s so great, that the working was stopped.

The iron mines of Dannemora, eleven leagues from Upsal, contain a large quant.i.ty of ice, according to a ma.n.u.script account by Mr.

Over-a.s.sessor-of-the-board-of-mines Winkler:[164] Jars, however, in his _Voyages Metallurgiques_,[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 fur 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 a.s.signed 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 compa.s.s of one day's walk.

Voigt[169] describes an _Eisgrube_ in the Rhongebirge, on the _Ringmauer_, the highest point of the _Tagstein_, where abundant ice is found in summer under irregular ma.s.ses 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 054 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 054 F. lower than in shafts some hundred feet higher; and the _Weiss Adler_ adit, on the left declivity of the valley of the Schwarzwa.s.ser, above the Antonshutte. 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. Air. Height above the sea.

Altenberg ... 42732 Fahr. 4127 2,450 feet Markus Rohling ... 43542 " 41832 1,870"

Johanngeorgenstadt. 43115 " 4109 2,460"

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

There is said to be an ice-cave in Na.s.sau, 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 glacieres 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 gla.s.s, 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 ma.s.ses of snow, and are of a dirty yellow colour.

At the back of this chamber, a narrow pa.s.sage 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 stalact.i.tes of ice are found in rich profusion, the latter being generally formed on small limestone stalact.i.tes, 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 Topfa.n.a.lva 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 stalact.i.tes 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 'coa.r.s.e-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 _s...o...b.._ by the natives.[172] The peasants a.s.sert 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. Boue[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.

FOOTNOTES:

[Footnote 122: Several of these caves are referred to by Reich, _Beobachtungen uber die Temperatur des Gesteins in verschiedenen Tiefen in den Gruben des Sachsischen Erzgebirges;_ Freiberg, 1834.]

[Footnote 123: _Naturwunder des Oesterr. Kaiserthums_, iii. 40.]

[Footnote 124: _Mittheil. des Oesterr. Alpen-Vereins_, ii. 441. I am indebted to G.C. Churchill, Esq., one of the authors of the well-known book on the Dolomite Mountains, for my knowledge of the existence of this cave, and of the Kolowrathohle.]

[Footnote 125: _Beschreibung merkwurdiger Hohlen_, ii. 283.]

[Footnote 126: _Geognostische Reschreibung des bayerischen Alpengebirges_; Gotha, 1861.]

[Footnote 127: These const.i.tute the upper bone bed and Dachstein limestone beds of the uppermost part of the Trias formation.]

[Footnote 128: _Hereynia Curiosa_, cap. v. The same account is given in Behren's _Natural History of the Harz Forest_, of which an English translation was published in 1730.]

[Footnote 129: See also Muncke, _Handbuch der Naturlehre_, iii. 277; Heidelberg, 1830.]

[Footnote 130: See page 58. The more modern spelling is _frais-puits_.]

[Footnote 131: liv. 292.]

[Footnote 132: Described by Schaller, _Leitmeritzer Kreis_, p. 271, and by Sommer, in the same publication, p. 331. I have not been able to procure this book.]

[Footnote 133: _Bohmens Topogr._, i. 339. This reference is given by Professor Pleischl.]

[Footnote 134: _Annalen_, lx.x.xi. 579.]

[Footnote 135: I was told, in 1864, by a chamois-hunter of Les Plans, a valley two hours above Bex, that some years before he was cutting a wood-road through the forest early in September, when, at a depth of 6 inches below the surface, he found the ground frozen hard. We visited the place together, but could find no ice. The whole ground was composed of a ma.s.s of loose round stones, with a covering of earth and moss, and the air in the interstices was peculiarly cold and dry.]

[Footnote 136: _Beobachtungen_, &c. (see note on p. 258), 181.]

[Footnote 137: Reich found the temperature of the ice to be 31982 F., that of the air in the immediate vicinity 34025, and the rock, at a little distance, 32765.]

[Footnote 138: iii. 150.]

[Footnote 139: See many careful descriptions of these caves in the _Annales de Chimie_; also, an account by Professor Ansted, in his _Science, Scenery, and Art_, p. 29. M. Chaptal (_Ann. de Chimie_, iv.

34) found the lowest temperature of the currents of cold air to be 365 F.; but M. Girou de Buzareingues _(Ann. de Chimie et de Phys_., xlv. 362) found that with a strong north wind, the temperature of the external air being 554 F., the coldest current gave 356 F.; with less external wind, still blowing from the north, the external air lost half a degree centigrade of heat, while the current in the cave rose to 3875 F. The cellars in which the famous cheese of Roquefort is ripened are not subterranean, but are buildings joined on to the rock at the mouths of the fissures whence the currents proceed. They are so valuable, that one, which cost 12,000 francs in construction, sold for 215,000 francs.