« AnteriorContinuar »
of Franconia, the Hartz and Carpathian mountains; and the uniformity generally observable in all these, led him to expect a scene of a similar character in that which he explored in the New World: but the reality far exceeded his expectations; for, if the structure of the cave resembled those he had elsewhere witnessed, the majesty of equinoctial vegetation gave an individual character and indescribable superiority to the entrance of the Cavern of the Guacharo. The entrance is a vaulted arch, eighty feet broad and seventy-two feet high; the steep rock that surmounts this opening is covered with gigantic trees, mixed with creeping and climbing plants and shrubs, brilliant with blossoms of the richest colours and the most varied forms. These form natural festoons, which hang from the mouth of the cave, and are gently agitated by the passing currents of air. Among them Humboldt enumerates a Dendrobium, an orchideous plant, with golden flowers spotted with black, and three inches long; a Bignonia, with a violet blossom; a purple Dolichos; and a magnificent Solandra, the deep orange flower of which has a fleshy tube four inches long. But this luxuriant vegetation was not alone confined to the exterior. The traveller, on following the banks of a subterranean stream into the grotto, beheld them, with astonishment, adorned for thirty or forty yards with the Praga palm tree, plantain-leaved heliconias, eighteen feet high, and arms that resembled trees in their size! It was not found necessary to light their torches till they had reached the distance of 430 feet, owing to the continuous direction of the cavern, which allows the light of day to penetrate thus far; and when this began to fail, the hoarse cries of the nocturnal birds began to be audible from a distance. The shrill discordant noise made by thousands of these birds, brought from the inmost recesses of the cave, and reverberated from the arched roofs, formed an indescribable clamour. The Indian guides, by fixing torches to the ends of long poles, showed the traveller the nests of the bird, which were constructed in funnel-shaped holes, with which the roof of the grotto was pierced in all directions, and generally at about sixty feet high. Still pursuing the course of the river, the cavern preserved the same width and height to the distance of 1458 feet from the mouth. The traveller, on turning round, was struck with the singularly beautiful appearance which a hill covered with the richest vegetation, immediately fronting the entrance of the grotto, presented. This, brilliantly illumined by the sun's rays, and seen through the vista of the dark cave, formed a striking contrast to the surrounding obscurity; while the large stalactites depending from the roof were relieved against the luminous back-ground of verdure. After surmounting, with some difficulty, an abrupt rise in the ground where the stream forms a small cascade, he found that the cave diminished in height to forty feet, but retained its original direction. Here a blackish mould was found, either brought by the rivulet, or washed down from the roof by the rain-water which penetrates the crevices of the rock; and in this he found seeds growing, which had been brought thus far by the birds, but so altered by the deprivation of light, that the species of plant, thus produced under such unfavourable circumstances, could not even be recognised. It was found impossible to persuade the Indian guides to advance further. The cries of the birds, rendered still more horrible by the contraction of the cave, had such an effect on their minds, that they absolutely refused to proceed; and, to the regret of Humboldt, he was compelled to retrace his steps.
Caverns, especially those which are situated in limestone, commonly present the formations called stalactites, from a Greek word signifying distillation or dropping. The manner of their production admits of a very plain and simple explanation. They proceed from water trickling through the roofs containing carbonate of lime, held in solution by carbonic acid. Upon exposure to the air the carbonic acid is gradually disengaged, and a pellicle of lime is deposited. The process proceeds, drop after drop, and, eventually, descending points hanging from the roof are formed, resembling icicles, which are com
posed of concentric rings of transparent pellicles of lime, presenting a very peculiar appearance, and, from their connection with each other, producing a variety of singular shapes. These descending points are the stalactites properly so called, from which the stalagmites are to be distinguished, which cover the floors of caverns with conical inequalities. These are produced by the evaporation of the larger drops which have fallen to the bottom, and are stalactites rising upwards from the ground. Frequently, in the course of ages, the ascending and descending points have been so increased as to meet together, forming natural columns, a series of which bears a striking resemblance to the pillars and arches of Gothic architecture.
The amount of this deposition which we find in caverns capable of producing it, is, in fact, enormous, and gives us an impressive idea of their extraordinary antiquity. The grotto of Antiparos-one of the islands of the Grecian Archipelago-is particularly celebrated on account of the size and diversity of form of these deposits. It extends nearly a thousand feet beneath the surface, in primitive limestone, and is accessible by a narrow entrance which is often very steeply inclined, but divided by level landing-places. After a series of descents, the traveller arrives at the Great Hall, as it is called, the sides and roof of which are covered with immense incrustations of calcareous matter. The purity of the surrounding stone, and the thickness of the roof in which the unfiltered water can deposit all impure admixtures, give to its stalactites a beautiful whiteness. Tall pillars stand in many places free, near each other, and single groups of stalagmites form figures so strongly resembling plants, that Tournefort endeavoured to prove from them a vegetable nature in stone. The remark of that intelligent traveller is an amusing example of over confidence: "Once again I repeat it, it is impossible this should be done by the droppings of water, as is pretended by those who go about to explain the formation of congelations in grottoes. It is much more probable that these other congelations we speak of, and which hang downwards or rise out different ways, were produced by our principle, namely, vegetation." The sight of the whole is described, by those who have visited this cavern, as highly imposing. In the middle of the Great Hall there is a remarkably large and fine stalagmite, more than twenty feet in diameter, and twenty-four feet high, termed the Altar, from the circumstance of the Marquis de Nointel, the ambassador from Louis XIV. to the Sultan, having caused high mass to be celebrated here in the year 1673. The ceremony was attended by five hundred persons; the place was illuminated by a hundred large wax torches; and four hundred lamps burned in the grotto, day and night, for the three days of the Christmas festival. This cavern was known to the ancient Greeks, but seems to have been completely lost sight of till the seventeenth century. Some of the caves of France and Germany have a high reputation for the number and beauty of their deposits; but the finest examples are found in the Cave of Adelsberg, to which reference has been made. The stalagmites here have formed two bridges over the subterranean river, which are situated almost a mile apart from each other, the inner one of which hangs suspended from eighty to a hundred fathoms over the abyss. An American visitor graphically describes some of the principal objects: "We advanced with ease," he states, "through the windings of the cavern, which at times was so low as to oblige us to stoop, and at times so high that the roof was lost in the gloom. But every where the most wonderful varieties of stalactites and crystals met our admiring view. At one time we saw the guides lighting up some distant gallery far above our heads, which had all the appearance of verandahs adorned with Gothic tracery. At another, we came into what seemed the long-drawn aisles of a Gothic cathedral, brilliantly illuminated. The whimsical variety of forms surpasses all the powers of description. Here was a butcher's shop, which seemed to be hung with joints of meat; and there, a throne with a magnificent canopy. There was the appearance of a statue with a
bearded head, so perfect that you could have thought it the work of a sculptor; and further on, toward the end of our walk, the figure of a warrior with a helmet and coat of mail, and his arms crossed, of the illusion of which, with all my efforts, I could not possibly divest my mind. Two stalactites, descending close to each other, are called, in a German inscription over them, with sentimentality truly German, the union of two hearts.' The resemblance is certainly very striking. After passing The Hearts,' we came to the Ball Room.' It is customary for the inhabitants of Adelsberg, and the surrounding country, to come on Whit-Monday to this grotto, which is brilliantly illuminated; and the part called the ball room is actually employed for that purpose by the peasantry. A gallery, very appositely formed by nature, serves the musicians for an orchestra; and wooden chandeliers are suspended from the vaulted roof. It is impossible for me to describe minutely all the wonderful varieties; the 'Fountains' seeming, as they fall, to be frozen into stone; the 'Graves,' with weeping willows waving over them; the 'Picture,' the 'Cannon,' the Confessional,' the 'Pulpit,' the 'Sausage-maker's Shop,' and the Prisons.' I must not omit mentioning one part, which, though less grand than many others, is extremely curious. The stalactites have here formed themselves like folds of linen, and are so thin as to be transparent. Some are like shirt-ruffles, having a hem, and looking as if they were embroidered; and there is one, called the 'Curtain,' which hangs exactly in natural folds like a white and pendent sheet. Every where you hear the dripping as of a continual shower, showing that the mighty work is still going on, though the several stages of its progress are imperceptible. Our attention was so excited, that we had walked two hours without feeling the least fatigue, or being sensible of the passage of time. We had gone beyond the point where most travellers had stopped, and had been rewarded for it by seeing stalactites of undiminished whiteness, and crystals glittering, as the light shone upon them, like unnumbered diamonds."
Stalactical depositions vary in colour according to the nature of the surrounding rocks, and Humboldt remarks in general that the formations occur more beautifully and completely in proportion as the caves are narrow and enclosed, since the deposition of crystals is less disturbed by the circulation of the surrounding air. On this account those of the wide open cavern of Caripe, which he explored, were far inferior to the stalactites of Adelsberg. In our own country the spot most remarkable for these formations is the Blue John mine, another of the celebrated places of the Peak, near its great cavern. This is a natural cavity, worked as a mine for the sake of obtaining the elegant fluor spar which gives its name to the site, and which is here found in small detached pieces in the limestone rock. Rude steps, leading downwards about sixty yards, conduct to a series of caverns and passages encrusted with depositions of lime, which have assumed a variety of interesting forms. In our illustrated instance, stalactites, of a delicate pearly yellow colour, of fine texture, and fantastically varied one from the other, have grown downwards until they rested upon some shelf of a lower stratum, probably of earthy matter. Arriving at such a plane, the waters in future spread more widely around, forming a deposit, and connecting the former stems with an inferior tablet of similar composition. The earthy or mineral stratum having been by some chance removed, the fairy columns attached to their kindred floor now remain suspended in middle space. These are graphically termed "the Organ." It is much to be regretted that a Continental reproach against us, that of an Englishman's eyes being in his fingers, here receives an illustration of its truth. Some unprincipled and vagabond sight-seers have wantonly mutilated this rarity, and deprived it of its earlier proportions, for which cause the relics are now upbraidingly exhibited in a rude wooden cage. Here, as at Antiparos, the principal subterranean apartment is termed the "Hall," a wide and lofty cavity, such as imagination conceives
would be a fitting home for the romantic outlaws pictured by Salvator Rosa, or described in the pages of Schiller. In this spot, not a long time ago, a popular
nobleman, who prosecuted adventurous researches in the most dangerous recesses of the mine, feasted a multitude of his friends, and made the wet rock resound to the toasts and sentiments imported from a more fashionable atmosphere. In a certain direction from this grand focus the visiter is led to a narrower and more irregular space, presenting a towering cupola, the grandeur of whose shivered sides can only be exhibited by drawing upwards, with cord and pulley, a round of lighted candles supplied by the conductor: these illuminate successively the varied and peculiar stages of the internal surface. The perpetual waters which trickle down have left a residuum of lime, which has been moulded, by accident, and by industrious and gentle operation, into a thousand free tresses and waving bands. The whole is fashioned by Nature with less of the abrupt form which characterises the congelation of fountain streams by cold, and presents a grotesque enamel of exquisite polish and gracefulness, giving to the artificial plain or coloured lights, uplifted within the conical abyss, beautiful reflections from its unrivalled crystallised surfaces. Frequently, while attention is riveted to the precinct of gloom and awful solitude, a chaunt of voices is heard from the summit of the dome, accessible by hidden performers from other avenues of the mine. The fleeting and distant expression of sound, with the mournful intervals of the strain, seems like a song of captive spirits, obedient to the rigid discipline of some invincible gnome.
The temperature of caverns exhibits great diversities, dependent upon their extent and form, and that of the same cavern will greatly vary at different seasons. In those which are dry and deep, covered with a thick stony roof, and withdrawn from the influence of the alteration of the external air, by having only a limited opening, the temperature can vary but little, and will continue through the whole year at nearly the same degree of warmth which is peculiar to their geographical situation. Before the warmer air of summer has so penetrated the roof that the temperature of the cavern can be somewhat
raised, the cooler air of the autumn and of the winter begins to penetrate; but before this lower temperature can establish itself, it is again overtaken by the warmth of the following spring and summer. The consequence of all this is a temperature subject to little alteration, but lower than the mean temperature of the surrounding atmosphere. The ancient Romans, hence, according to Seneca, were accustomed to erect their country seats in the vicinity of those natural cavities which abound about the capital, for the purpose of enjoying their refreshing chilliness in the summer season. It was in one of these volcanic caverns that Tiberius was nearly destroyed while at supper; for, during the banquet, the roof suddenly gave way, and buried several of his attendants beneath its ruins, when Sejanus threw himself upon the emperor to preserve him from the falling
Many caverns, however, vary greatly in their temperature, and exhibit the appa rently strange anomaly of being cold when the external air is warm, and warm when it is cold, in some instances carrying this contrast to the extreme, so as to be coated with ice amid the heat of summer, and affording a comfortable warmth amid the cold of winter. In the neighbourhood of Szelitze, a village of Hungary, there is a cave in the transition limestone of the Carpathians which displays this phenomenon. The country in the vicinity abounds with woods, and the air is sharp and cold. The entrance of the cavern, which fronts the north, is eighteen fathoms high, and eight broad; consequently, wide enough to receive a large supply of external air, which here generally blows with great violence; but the subterranean passages, which consist entirely of solid rock, winding round, stretch away farther to the north than has been yet discovered. In the midst of winter the air in this cavern is warm; but in summer, when the heat of the sun without is scarcely supportable, the cold within is not only very piercing, but so intense that the roof is covered with icicles of great size, which, spreading into ramifications, form very grotesque figures. When the snow melts, in spring, the inside of the cave, where its surface roof is exposed to the sun, emits a pellucid water, which immediately congeals as it drops, and thus forms the above icicles, and the very water that drops from them on the sandy ground freezes in an instant. It is even observed that the greater the heat is without, the more intense is the cold within, so that in the dog days all parts of this cavern are covered with ice, which the inhabitants use for cooling their liquors. The quantity of ice is so great that a narrator estimates that it would require six hundred waggons to remove it in a week. In autumn, when the nights grow cold and the heat of the day begins to abate, the ice in the cavern begins to dissolve, so that by winter no more ice is seen. The cavern then becomes perfectly dry, and has a mild warmth. At that season it is the haunt of swarms of flies, gnats, bats, owls, and even of hares and foxes that resort hither, as to their winter retreat, and remain till the return of spring. An instance almost as singular occurs at Besançon, in a grotto which extends 364 feet into the rock, the mouth of which, like that of Szelitze, is towards the north, and covered with vegetation. During the whole summer this cavern contains masses of ice, which melt away in October and November.
This apparently anomalous phenomenon is supposed to be capable of being explained by the relation which subsists between the moisture in these caverns and the external air. When it is hot and dry outside, as in summer, evaporation takes place, and by this means a considerable degree of warmth is withdrawn from the enclosed air, the vapours making their escape through the openings, and through fissures in the roofs. The greater the exterior temperature the more vigorously the evaporation is carried on, producing a degree of cold in the interior which may sink beneath the freezing point, just as in the greatest heat we can most readily freeze water if we surrround it with ether. It is upon this principle that travellers, in some regions, are accustomed to cool their drinks, which they bury in