The blocks of ice were by this time becoming rather small; and as we had now once more reached the region of lavender, we cut a large quantity and wrapped the ice in it, and thus protected it from further thaw. For some time before arriving at the farm where my companion's partner lived, he indulged in praises of the wine which their vineyard produced, and assurances of the safety with which it would perform a journey to England. He urged its excellent bouquet, and gave me a card of prices which certainly seemed marvellously reasonable. Finally, he proposed to join me at a bottle of white muscat, from the farmer's cave, in order that I might have an opportunity of seeing how true was his account of the wine. We seated ourselves accordingly in the farmyard, and drank a bottle of delightful wine at 65 centimes the bottle, clear and sparkling, and with a strong muscat flavour. Liotir combined with it intoxication of a different kind, and showed unmistakeable signs of his determination to take another member of the farmer's household into partnership,--the mysterious friend, in fact, for whose astonishment the ice was intended. The white muscat, they told me, would not keep over the year; but they had a wine at the same price which they highly recommended, and warranted to keep for a considerable number of years. Liotir was very anxious that we should have a bottle of this, for he was confident that I should give them an order if I once tasted it; but we had been in at the death of so many bottles that day, that I declined to try the muscat rosat. I have since had a hundred litres sent over by Liotir, and find it very satisfactory. It has a rich, clear, port-wine colour, sparkling, and with the true frontignac flavour.
The effect of the wine on Liotir was peculiar. In the earlier part of the walk, he had never seen Algeria; but after half a bottle of muscat, he had spent six months in that country, and he enlivened the remainder of the way with many details of his experiences there. We reached Die about half-past seven, and the arrival of real ice was hailed as a marvel. Although I had been sent off so unhesitatingly by the landlord in the morning, it seemed that they none of them knew what a glacière meant. They had determined that we should never reach the Foire de Fondeurle, and that if we did, we should find nothing there to repay our toil. As I sat at an open window afterwards, Liotir's voice was to be heard holding forth in a neighbouring café upon the wonders of the day; and among the crowd which is a normal condition of the evening streets of Die, the words Fondeurle, Vassieux, Anglais, glace, &c., showed what the general subject of conversation was.
The landlady had obeyed orders, and was provided with butter and bread. The tea was served in an open earthenware pitcher, with the spout at right angles with the handle. There was no cup; but the woman remarked that if monsieur was particular about that, he could turn out the sugar and use the basin, which he did. The milk had a basin to itself; but it had offered so large and tempting a surface to the flies of the town, that it remained untouched. The knife and spoon were imbued with ineradicable garlic, and my own trusty clasp-knife was the only weapon I could use for all table purposes. If it had not been for the ice and the lavender, I think I should never have got away from Die. The former made it possible to eat some bread-and-butter; and of the latter I made a sort of respirator for nose and mouth, which modified the odour of cocks and hens prevailing in the house.
Next morning the diligence was to start early, and, in preparation for the six hours' drive, I ordered two eggs to be boiled for breakfast. As the first proved to have been boiled in tepid water, I requested the landlady to boil the second afresh, which she did in a manner that may partly account for the observed fact that the very eggs of some towns taste of garlic. There was household soup simmering on the fire, reeking with onion and garlic, and many other abominations; and, as if it was quite the right and usual thing to do, she slipped the unfortunate egg into this, and left it there to be cooked. After all, garlic must be cheap as an article of food, for the whole bill amounted only to 7-1/2 francs.
This was the last glacière on my list. It was quite as well that such was the case; for the trials of Dauphiné had been too great, and I should scarcely have been inclined to face further adventures of a like kind.
Matthew Bell, the historian of Hungary, sent an account of this cavern to England, in the middle of the last century, which was printed in the original Latin in the 'Philosophical Transactions' of 1739-40 (pp. 41, &c.).
This account states that the cave is in the county of Thorn,[99] among the lowest spurs of the Carpathians. The entrance, which faces the north, and is exposed to the cold winds from the snowy part of the Carpathian range, is 18 fathoms high and 9 broad; and the cave spreads out laterally, and descends to a point 50 fathoms below the entrance, where it is 26 fathoms in breadth, and of irregular height. Beyond this no one had at that time penetrated, on account of the unsafe footing, although many distant echoes were returned by the farther recesses of the cave; indeed, to get even so far as this, much step-cutting was necessary.
When the external frost of winter comes on, the account proceeds, the effect in the cave is the same as if fires had been lighted there: the ice melts, and swarms of flies and bats and hares take refuge in the interior from the severity of the winter. As soon as spring arrives, the warmth of winter disappears from the interior, water exudes from the roof and is converted into ice, while the more abundant supplies which pour down on to the sandy floor are speedily frozen there. In the Dog-days, the frost is so intense that a small icicle becomes in one day a huge mass of ice; but a cool day promptly brings a thaw, and the cave is looked upon as a barometer, not merely feeling, but also presaging, the changes of weather. The people of the neighbourhood, when employed in field-work, arrange their labour so that the mid-day meal may be taken near the cave, when they either ice the water they have brought with them, or drink the melted ice, which they consider very good for the stomach. It had been calculated that 600 weekly carts would not be sufficient to keep the cavern free from ice. The ground above the cave is peculiarly rich in grass.
In explanation of these phenomena, Bell threw out the following suggestions, which need no comment. The earth being of itself cold and damp, the external heat of the atmosphere, by partially penetrating into the ground, drives in this native cold to the inner parts of the earth, and makes the cold there more dense. On the other hand, when the external air is cold, it draws forth towards the surface the heat there may be in the inner part of the earth, and thus makes caverns warm. In support and illustration of this view, he states that in the hotter parts of Hungary, when the people wish to cool their wine, they dig a hole 2 feet deep, and place in it the flagon of wine, and, after filling up the hole again, light a blazing fire upon the surface, which cools the wine as if the flagon had been laid in ice. He also suggests that possibly the cold winds from the Carpathians bring with them imperceptible particles of snow, which reach the water of the cave, and convert it into ice. Further, the rocks of the Carpathians abound in salts, nitre, alum, &c., which may, perhaps, mingle with such snowy particles, and produce the ordinary effect of the snow and salt in the artificial production of ice.
Townson[100] visited this cave half a century later, and concluded that Bell was in error with regard to the supposed winter thaw and summer frost, although he himself received information at Kaschau which corroborated the earlier account. He describes the approach to the village of Szilitze as leading by a by-road through a pleasant country of woods and hills, with much pasture-land, the cave lying a mile beyond the village, and displaying an entrance 100 feet broad, and 20 or 30 feet high, turned towards the north. The descent of the floor of the cave is rapid, and was covered with thin ice, at the time of his visit, for the last third of the way: from the roof at the farther end, where the cave is not so high as at the entrance, a congeries of icicles was seen to hang; and in a corner on the right, completely sheltered from the rays of the sun, there was a large mass of the same material. It was a fine forenoon in July, and all was in a state of thaw, the icicles dropping water, and the floor of ice covered with a thin layer of water; while the thermometer in all parts of the cave stood at zero of Réaumur's scale. The rock is compact unstratified limestone, in which so many of the famous caverns of the world are found.
The Cave of Yeermalik, in Koondooz[101]In the year 1840, Captain Burslem, of the 13th Light Infantry, made an expedition from Cabul to the North-west, accompanied by Lieutenant Sturt of the Bengal Engineers, who was afterwards killed in the terrible pass where Lady Sale, whose daughter he had married, was shot through the arm.
After crossing the high and wild pass of Karakotul (10,500 feet), these travellers reached the romantic glen of the Doaub, which lies at the foot of the pass, and is surrounded on all sides by lofty mountains. Here they were hospitably entertained by Shah Pursund Khan, the chief of the small territory, and their curiosity was roused by the account given by an old moollah of a cavern seven miles off, which the Shah strongly advised them not to attempt to visit, for the Sheitan (the devil), whose ordinary place of abode it was, never allowed a stranger to return from its recesses. The moollah, however, scouted this idea, on the ground that it was much too cold for such an inhabitant; and the Shah eventually agreed to accompany them to the cave with a band of his followers.
As they rode through long and rich grass, following the course of a gentle stream, and tormented by swarms of forest flies, or blood-suckers, the Shah informed them that he had once endeavoured to explore the cave, and had already penetrated to a considerable distance, when he came upon the fresh prints of a naked foot, with an extraordinary impression by their side, which he suspected to be the foot of Sheitan himself, and so he beat a precipitate retreat. The moollah told them that there was a large number of skeletons in the cave, the remains of 700 men who took refuge there during the invasion of Genghis Khan, with their wives and families, and defended themselves so stoutly, that, after trying in vain the means by which the M'Leods were destroyed in barbarous times, and the opponents of French progress in Algeria in times less remote, the invader built them in with huge natural blocks of stone, and left them to die of hunger.
The entrance is half-way up a hill, and is 50 feet high, with about the same breadth. Not far from the entrance they found a passage between two jagged rocks, possibly the remains of Genghis Khan's fatal wall, so narrow that they had some difficulty in squeezing through; and then, before long, came to a drop of 16 feet, down which they were lowered by ropes made from the cotton turbans of the Shah and his attendants. Here they left two men to haul them up on their return, and bade farewell to the light of day. The narrow path led by the edge of a black abyss, sometimes over a flooring of smooth ice for a few feet, and widened gradually till they reached a damp and dripping hall, of dimensions so vast that the light of their torches did not enable them to form a conception of its size. In this hall they found hundreds of skeletons in a perfectly undisturbed state, one, for instance, still holding the skeletons of two infants in its bony arms, while some of the bodies had been preserved, and lay shrivelled like those at the Great St. Bernard. They were very much startled here by the discovery of the prints of a naked human foot, and by its side the distinct mark of the pointed heel of an Affghan boot,[102] precisely what had so thoroughly frightened the Shah twelve years before. The prints retained all the sharpness of outline which marks a recent impression, and led towards the farther recesses of the cave; but the Englishmen were called away from their investigation by the announcement that if they did not make haste, there would not be oil enough for lighting them to the ice-caves.
Proceeding through several low arches and smaller caves, they reached at length a vast hall, in the centre of which was[103] 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, the walls of which were nearly 2 feet thick; the floor, sides, and roof were smooth and slippery, and their figures were reflected from floor to ceiling and from side to side in endless repetition. The inside of this chilly abode 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.
The cavern in which this marvellous mass of ice stood, branched off into numerous galleries, one of which led the party to a sloping platform of rapidly increasing steepness, where they were startled by the reappearance of the naked foot-prints, passing down the slope. The toes were spread out in a manner which showed that they belonged to some one who had been in the habit of going barefoot, and Captain Burslem took a torch and determined to trace the steps: a large stone, however, gave way under his weight; and this, sliding down at first, and then rolling and bounding on for ever, raised such a tumult of noise and echoes that the natives with one accord cried 'Sheitan! Sheitan!' and fled precipitately, extinguishing all the lights in their fear; so that but for Sturt's torch the whole party must have been lost in the darkness. Shah Pursund Khan at once called a retreat, vowing that it was of no use to attempt to follow the footsteps, as it was well known that the cave extended to Cabul! The guides had now lost their small allowance of pluck, and wandered about despairingly for a long time before they could find their way back to the ice-cave, and thence to the foot of the rock where the two men and the turban-ladders had been left. As soon as they came in sight of this, their comrades above cried out to them that they must make all haste, for Sheitan himself had appeared an hour before, running along the ledge where they now were, and finally vanishing into the gloom beyond; an announcement which of course produced a stampede in the terrified party of natives. Five or six rushed to the spot where the turbans hung, and only an opportune fall of stones from above prevented their destroying the apparatus in their blind hurry to escape. The chief claimed the privilege of being drawn up first, and he and all his followers declared that nothing should ever tempt them to visit again the Cave of Yeermalik.[104]
The Surtshellir, in Iceland.The first account of this lava-cavern is given by Olafsen,[105] who visited it in 1750 and 1753. Ebenezer Henderson[106] explored it in 1815, and Captain Forbes gives some account of it in his recent book on Iceland.[107] It is mentioned in some of the Sagas,[108] and appears to have been a refuge for robbers in the tenth century, and Sturla Sigvatson, with a large band of followers, spent some time here. The Landnama Saga derives the name Surtshellir from a huge giant called Surtur, who made his abode in the cave; but Olafsen believed that the name merely meant black hole, from surtur or svartur, and was due to the darkness of the cave and the colour of the lava: in accordance with this view, it is called Hellerin Sortur, or black hole, in some of the earlier writings. The common people are convinced that it is inhabited by ghosts; and Olafsen and his party were assured that they would be turned back by horrible noises, or else killed outright by the spirits of the cave: at any rate, their informants declared they would no more reach the inner parts of the cavern than they had reached the traditional green valley of Aradal, isolated in the midst of glaciers, with its wild population of descendants of the giants, which they had endeavoured to find some time before.[109]
The cave is in the form of a tunnel a mile or more in length, with innumerable ramifications, in the lava which has flowed from the Bald Yökul. It lies on the edge of the uninhabited waste called the Arnavatns-heidi, in a district described by Captain Forbes as distorted and devilish, a cast-iron sea of lava. The approach is through an open chasm, 20 to 40 feet in depth, and 50 feet broad, leading to the entrance of the cave, where the height is between 30 and 40 feet, and the breadth rather more than 50. Henderson found a large quantity of congealed snow at this entrance, and along pool of water resting on a floor of ice, which turned his party back and forced them to seek another entrance, where again they found snow piled up to a considerable height. Olafsen also mentions collections of snow under the various openings in the lava which forms the roof of the cave. The latter explorer discovered interesting signs of the early inhabitants of the Surtshellir, as, for instance, the common bedstead, built of stones, 2-1/2 feet high, 36 feet long, and 14 feet broad, with a pathway down the middle, forming the only passage to the inner parts of the cave. The spaces enclosed by these stones were strewn with black sand, on which rough wool was probably laid by way of mattress. This could scarcely have been a bedstead in the time of the giants, for a total breadth of 14 feet, deducting for the pathway down the middle, will not give more than 6 feet for the layer of men on either side, unless indeed they lay parallel to the passage, and required a length of 36 feet. He also found an old wall, built with blocks of lava across one part of the cave, as if for defence, and a large circular heap of the bones of sheep and oxen, presumably the remains of many years of feasting. Captain Forbes scoffs at these bones, and suggests errant wild ponies as the depositors thereof.
Olafsen had found in his earlier visit that the way was stopped, far in the recesses of the cave, by a lake of water, which filled the tunnel to a depth of 3 feet or more, lying on ice; but in 1753 there was not more than a foot of water, through which they waded without much difficulty. The air soon became exceedingly cold and thick, and for some hundreds of paces they saw no light of day, till at length they reached a welcome opening in the roof. Beyond this, the air grew colder and more thick, and the walls were found to be sheeted with ice from roof to floor, or covered with broad and connected icicles. The ground also was a mass of ice, but an inch or two of fine brown earth lay upon it, which enabled them to keep their footing. This earth appeared to have been brought down by the water which filtered through the roof. 'The most wonderful thing,' Olafsen remarks, 'that we noticed here, was, that the stalactites of ice were set with regular figures of five and seven sides, joined together, and resembling those seen on the second stomach of ruminating animals. The condensed cold of the air must have imparted these figures to the ice; they were not external (merely?), but in the ice itself, which otherwise was clear and transparent.'
Henderson and his party appear to have had much more wading to do than Olafsen, walking in one instance through a long tract of water up to the knees. In the deeper recesses of the cave, apparently in the part where the earlier explorers had found the reticulated ice, they found the whole floor of the passage covered with thick ice, with so steep a dip that they sat down and slid forward by their own weight--a most undignified proceeding for a grave gentleman on a mission from the Bible Society. On holding their torches close to the floor, they saw down to a depth of 7 or 8 feet, the ice being as clear as crystal. 'The roof and sides of the cave were decorated with most superb icicles, crystallised in every possible form, many of which rivalled in minuteness the finest zeolites; while from the icy floor rose pillars of the same substance, assuming all the curious and phantastic shapes imaginable, mocking the proudest specimens of art, and counterfeiting many well-known objects of animated nature. Many of them were upwards of 4 feet high, generally sharpened at the extremity, and about 2 feet in thickness. A more brilliant scene perhaps never presented itself to the human eye, nor was it easy for us to divest ourselves of the idea that we actually beheld one of the fairy scenes depicted in Eastern fable. The light of the torches rendered it peculiarly enchanting.'
Captain Forbes found much ice on the floor, but he did not enjoy the cold and wet, and seems to have ascended by the last opening in the roof, mentioned by Olafsen, before reaching the cavern where the more beautiful parts of the ice-decoration were found by his predecessors. The two engravings of the interior of the cave given in his book are copied from the magnificent lithographs of Paul Gaimard,[110] but much of the effect has been lost in the process of copying.
Mr. Baring Gould mentions this cavern in his book on Iceland, and believes that its interest has been much overrated. He seems to have visited the cave, but makes no allusion to the existence of ice.[111]
Mr. E.T. Holland visited the Surtshellir in the course of his tour in Iceland, in 1861, and an account of his visit is given in the first volume of 'Peaks, Passes, and Glaciers.'[112] After following in Olafsen's steps for some time, the party reached a cave whose floor was composed of very clear ice, apparently of great thickness, for they could not see the lava beneath it. The walking on this smooth ice-floor Mr. Holland describes as being delightful, the whole sloping considerably downwards. 'In five minutes,' he continues, 'we reached the most beautiful fairy grotto imaginable. From the crystal floor of ice rose up group after group of transparent icy pillars, while from the glittering roof most brilliant icy pendants hung down to meet them. Columns and arches of ice were ranged along the crystalline walls ... I never saw a more brilliant scene; and indeed it would be difficult to imagine anything more fairy-like. The pillars were many of them of great size, tapering to a point as they rose. The largest were at least 8 feet high, and 6 feet in circumference at their base. The stalactites were on an equally grand scale. Through this lovely ice-grotto we walked for nearly ten minutes.'
The temperature of the caves, Mr. Holland states in a note, was from 8° to 10° C. (46·4° to 50° F.), that of the air outside being 53·6° F.
The Gypsum Cave of Illetzkaya-Zastchita, in the Steppes of the Kirghis, South of Orenburg.
The district in which this cavern occurs is a small green oasis on the undulating steppe, lying on a vast bed of rock-salt, which extends over an area of two versts in length, and a mile in breadth, with a thickness of more than 100 feet. When the thin cover of red sand and marl is removed, the white salt is exposed, and is found to be so free from all stain, or admixture of other material, excepting sometimes minute filaments of gypsum, that it is pounded at once for use, without any cleansing or recrystallising process.
In the immediate neighbourhood of Illetzkaya-Zastchita there are two or three gypseous hillocks, and a cavern in one of these is used by the inhabitants as a cellar, having been artificially enlarged for that purpose. Sir Roderick Murchison and his colleagues visited this cavern on a hot day in August, with the thermometer at 90° in the shade, in the course of their travels under the patronage of the late Emperor of Russia.[113] They found the hillock to be an irregular cone 150 feet in height; the entrance was by a frail door, on a level with the village street, and fully exposed to the rays of the sun; and yet, when the door was opened, so piercing a current of cold air poured forth, that they were glad to beat a retreat for a while; and on eventually exploring farther, they found the quass and provisions, stored in the cave, half-frozen within three or four paces of the door. The chasm soon opened out into a natural vault from 12 to 15 feet high, 10 or 12 paces long, and 7 or 8 in width, which seemed to have numerous small ramifications into the impending mound of gypsum and marl. The roof of this inner cavern was hung with undripping solid icicles, and the floor was a conglomerate of ice and frozen earth. They were assured that the cold is always greatest within when the external air is hottest and driest, and that the ice gradually disappears as winter approaches, and vanishes when the snow comes. The peasants were unanimous in these statements, and asserted that they could sleep in the cave without sheepskins in the depth of winter.
Sir Roderick Murchison and his friends were at first inclined to explain these phenomena by supposing that the chief fissure communicated with some surface of rock-salt, 'the saliferous vapours of which might be so rapidly evaporated or changed in escaping to an intensely hot and dry atmosphere as to produce ice and snow.' But Sir John Herschel, to whom they applied for assistance, rejected the evaporation theory, and suggested that the external summer wave of heat might possibly only reach the cave at Christmas, being delayed six months in its passage through the rock; the cold of winter, in the same manner, arriving at midsummer. To this the explorers objected, that the mound contained many caves, but' only in this particular fissure was any ice found. Dr. Robinson, astronomer at Armagh, endeavoured to explain the matter by referring to De Saussure's explanation of the phenomena of cold caves in Italy and elsewhere; but this, too, was considered unsatisfactory. At length, Professor Wheatstone referred them to the memoir by Professor Pictet, in the Bibliothèque Universelle of Geneva, where that savant improves upon De Saussure's theory, and applies it in its new form to the case of caves containing permanent ice, in tracts whose mean cold is above the freezing point. This they seem to have accepted, adding that the climatological circumstances of Orenburg--a wet spring, caused by the melting of the abundant snows, followed by a summer of intense and dry Asiatic heat--must be particularly favourable for the working out of the theory, and must also act powerfully in producing the refrigerating effects of evaporation.[114]
The traveller Pallas visited Illetzkaya in July 1769, and describes this gypseous hillock.[115] In his time the entrance by the side of the hill was unknown, as also was the existence of ice in the cavern. He saw at the top of the Kraoul-naï-Gora, or Watch-mountain, as it was called, a fissure which had once formed a large cavern, into which the Kirghis were in the habit of throwing furs and other materials as religious offerings. Although the cave had since fallen in, they still kept up a part of the ceremony, marching solemnly round the base of the hill once a year, and bathing in the neighbouring water. In earlier times, a man had descended through the fissure by means of cords, and found the cold within insupportable, having very probably reached the present ice-cave.
Pallas describes many caves in various parts of Russia, but never seems to hint at the existence of ice in them, though he specially mentions their extreme cold. Some of these occurred in gypsum, and some in limestone; and the gypseous caves showed universally a very low temperature, though still far above the freezing-point.[116]: Thus in the dark cavern of Barnoukova,[117] on the Piana, in a rock of gypsum, while the thermometer in the shade stood at 75°•2, the temperatures at various points in the cave were,--at the entrance 59°•36, 25 feet from the entrance 46°•4, and in the coldest part 42°•8. This cold he describes as insupportable. The temperature of the water which had accumulated in the coldest parts of the cave was 48°•8, considerably higher than the surrounding atmosphere; from which Pallas concluded that the cold of gypsum-caves is due to the acid vapours which are generally observed in grottoes of this description. In May 1770, he found snow on the sloping entrance to the cavern of Loeklé, in the neighbourhood of the Oufa; but the air of the interior was not colder than was to be expected in a deep cave.
Sir R. Murchison wrote to Russia for further information with respect to this cave in January 1865, and again in the beginning of April, addressing his second enquiry to the Secretary of the Imperial Academy. In reply, the Secretary says that he is not aware that any thermometric observations have been made in the cavern. He encloses a short statement by M. Helmersen, one of the members of the Academy, to the following effect:--About 50 versts SE. of Miask, in the chain of the Ural, is a copper mine, called Kirobinskoy, which was abandoned more than fifty years ago. On the 7th July, 1826, M. Helmersen found a thick wainscoting of ice on the sides and roof and floor of the horizontal gallery, within 10 feet of the entrance. He was assured that this ice never melts, and that its thickness is greater in summer than in winter. M. Helmersen adds, that to the best of his belief no one has investigated the cavern of Illetzkaya Zastchita since Sir R. Murchison's visit.
The Ice-Cavern of the Peak of Teneriffe.[118]This cave is at a height of 11,040 feet above the sea, and is therefore not far below the snow-line of the latitudes of the Canary Isles. The entrance is by a hole 3 or 4 feet square, in the roof of the cave, which may be about 20 feet from the floor. The peasants who convey snow and ice from the cave to the lower regions, enter by means of knotted ropes; but Professor Smyth had caused his ship's carpenter to prepare a stout ladder, by which photographic instruments and a lady were taken down.
On alighting on a heap of stones at the bottom, the party found themselves surrounded by a sloping wall of snow, 3 feet high, and 7 or 8 feet broad, the basin in which they stood being formed in the snow by the vertical rays of the sun, and by the dropping of water from the edges of the hole.[119] Beyond this ring-fence, large surfaces of water stretched away into the farther recesses of the cave, resting on a layer of ice, which appeared to be generally about 2 feet thick. At one of the deeper ends of the cave, water dropped continually from the crevices of the roof; a fact which Professor Smyth attributed to the slow advance of the summer wave of heat through the superincumbent rock, which was only now reaching the inner recesses of the loose lava, and liquefying the results of the past winter. There would seem to be immense infiltration of meteoric water on the Peak; for, notwithstanding the great depth of rain which falls annually in a liquid or congealed form, the sides of the mountain are not scored with the lines of water-torrents.
Though occurring in lava, this cavern is quite different from lava-tunnels, such as the Surtshellir, which are recognised formations, produced by the cooling of the terminal surface-crust of the stream of lava, and the subsequent bursting forth of the molten stream within. This, on the contrary, proved to be a smooth dome-shaped cave, running off into three contracting lobes or tunnels which might be respectively 70, 50, and 40 feet long, and were all filled to a certain depth with water: in the smoothness of the interior surfaces, Professor Smyth believed that he detected the action of highly elastic gases on a plastic material.
The astronomer takes exception to the term 'underground glacier' [120] which had been applied to this cavern. He represents that the mountain is abundantly covered each winter with snow, in the neighbourhood of the ice-cave, which is nearly within the snow-line, and the stores of snow thus accumulated in the cave have no great difficulty in resisting the effects of summer heat, since all radiation is cut off by the roof of rocks. The importance of this protection may be understood from the fact that in the middle of July the thermometer at this altitude gave 130° in the sun, but fell to 47° when relieved from the heat due to radiation. At the time of this observation, there were still patches of snow lying on the mountain-side, exposed to the full power of direct radiation; and, therefore, there is not anything very surprising in the permanence of snow under such favourable circumstances as are developed in the cave. Mr. Airy, a few summers ago, found the rooms of the Casa Inglese, on Mount Etna, half filled with snow, which had drifted in by an open door, and had been preserved from solar radiation by the thick roof.[121]
Humboldt remarks, that the mean temperature of the region in which the Cueva del Hielo (ice-cave) occurs, is not below 3° C. (37·4° F.), but so much snow and ice are stored up in the winter that the utmost efforts of the summer heat cannot melt it all. He adds, that the existence of permanent snow in holes or caves must depend more upon the amount of winter snow, and the freedom from hot winds, than on the absolute elevation of the locality.
The natives of Teneriffe are men of faith. They have large belief in the existence and intercommunication of numerous vast caverns in the Peak, one of which, on the north coast, is said to communicate with the ice-cavern, notwithstanding 8 miles of horizontal distance, and 11,000 feet of vertical depth. The truth of this particular article of their creed has been recently tested by several worthy and reverend hidalgos, who drove a dog into the entrance of the cavern on the sea-coast, in the belief that he would eventually come to light again in the ice-cave: he was accordingly found lying there some days after, greatly fatigued and emaciated, having in the interval accomplished the 11,000 feet of subterranean climbing. How he could enter, from below, a water-logged cave, does not appear to have been explained.
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]