An alley of perseas led us to the Hospital of the Aragonese Capuchins. We stopped near a cross of Brazil-wood, erected in the midst of a square, and surrounded with benches, on which the infirm monks seat themselves to tell their rosaries. The convent is backed by an enormous wall of perpendicular rock, covered with thick vegetation. The stone, which is of resplendent whiteness, appears only here and there between the foliage. It is difficult to imagine a more picturesque spot. It recalled forcibly to my remembrance the valleys of Derbyshire, and the cavernous mountains of Muggendorf, in Franconia. Instead of the beeches and maple trees of Europe we here find the statelier forms of the ceiba and the palm-tree, the praga and irasse. Numberless springs gush from the sides of the rocks which encircle the basin of Caripe, and of which the abrupt slopes present, towards the south, profiles of a thousand feet in height. These springs issue, for the most part, from a few narrow crevices. The humidity which they spread around favours the growth of the great trees; and the natives, who love solitary places, form their conucos along the sides of these crevices. Plantains and papaw trees are grouped together with groves of arborescent fern; and this mixture of wild and cultivated plants gives the place a peculiar charm. Springs are distinguished from afar, on the naked flanks of the mountains, by tufted masses of vegetation* which at first sight seem suspended from the rocks, and descending into the valley, they follow the sinuosities of the torrents.*
[* Among the interesting plants of the valley of Caripe, we found for the first time a calidium, the trunk of which was twenty feet high (C. arboreum); the Mikania micrantha, which may probably possess some of the alexipharmic properties of the famous guaco of the Choco; the Bauhinia obtusifolia, a very large tree, called guarapa by the Indians; the Weinnannia glabra; a tree psychotria, the capsules of which, when rubbed between the fingers, emit a very agreeable orange smell; the Dorstenia Houstoni (raiz de resfriado); the Martynia Craniolaria, the white flowers of which are six or seven inches long; a scrophularia, having the aspect of the Verbascum miconi, and the leaves of which, all radical and hairy, are marked with silvery glands.]
We were received with great hospitality by the monks of Caripe. The building has an inner court, surrounded by an arcade, like the convents in Spain. This enclosed place was highly convenient for setting up our instruments and making observations. We found a numerous society in the convent. Young monks, recently arrived from Spain, were just about to settle in the Missions, while old infirm missionaries sought for health in the fresh and salubrious air of the mountains of Caripe. I was lodged in the cell of the superior, which contained a pretty good collection of books. I found there, to my surprise, the Teatro Critico of Feijoo, the Lettres Edifiantes, and the Traite d’Electricite by abbe Nollet. It seemed as if the progress of knowledge advanced even in the forests of America. The youngest of the capuchin monks of the last Mission had brought with him a Spanish translation of Chaptal’s Treatise on Chemistry, and he intended to study this work in the solitude where he was destined to pass the remainder of his days. During our long abode in the Missions of South America we never perceived any sign of intolerance. The monks of Caripe were not ignorant that I was born in the protestant part of Germany. Furnished as I was with orders from the court of Spain, I had no motives to conceal from them this fact; nevertheless, no mark of distrust, no indiscreet question, no attempt at controversy, ever diminished the value of the hospitality they exercised with so much liberality and frankness.
The convent is founded on a spot which was anciently called Areocuar. Its height above the level of the sea is nearly the same as that of the town of Caracas, or of the inhabited part of the Blue Mountains of Jamaica. Thus the mean temperatures of these three points, all situated within the tropics, are nearly the same. The necessity of being well clothed at night, and especially at sunrise, is felt at Caripe. We saw the centigrade thermometer at midnight, between 16 and 17.5°; in the morning, between 19 and 20°. About one o’clock it had risen only to 21, or 22.5°. This temperature is sufficient for the development of the productions of the torrid zone; though, compared with the excessive heat of the plains of Cumana, we might call it the temperature of spring. Water exposed to currents of air in vessels of porous clay, cools at Caripe, during the night, as low as 13°.
Experience has proved that the temperate climate and rarefied air of this spot are singularly favourable to the cultivation of the coffee-tree, which is well known to flourish on heights. The prefect of the capuchins, an active and enlightened man, has introduced into the province this new branch of agricultural industry. Indigo was formerly planted at Caripe, but the small quantity of fecula yielded by this plant, which requires great heat, caused the culture to be abandoned. We found in the conuco of the community many culinary plants, maize, sugar cane, and five thousand coffee-trees, which promised a fine harvest. The friars were in hopes of tripling the number in a few years. We cannot help remarking the uniform efforts for the cultivation of the soil which are manifested in the policy of the monastic hierarchy. Wherever convents have not yet acquired wealth in the New Continent, as formerly in Gaul, in Syria, and in the north of Europe, they exercise a happy influence on the clearing of the ground and the introduction of exotic vegetation. At Caripe, the conuco of the community presents the appearance of an extensive and beautiful garden. The natives are obliged to work in it every morning from six to ten, and the alcaldes and alguazils of Indian race overlook their labours. These men are looked upon as great state functionaries, and they alone have the right of carrying a cane. The selection of them depends on the superior of the convent. The pedantic and silent gravity of the Indian alcaldes, their cold and mysterious air, their love of appearing in form at church and in the assemblies of the people, force a smile from Europeans. We were not yet accustomed to these shades of the Indian character, which we found the same at the Orinoco, in Mexico, and in Peru, among people totally different in their manners and their language. The alcaldes came daily to the convent, less to treat with the monks on the affairs of the Mission, than under the pretence of inquiring after the health of the newly-arrived travellers. As we gave them brandy, their visits became more frequent than the monks desired.
That which confers most celebrity on the valley of Caripe, besides the extraordinary coolness of its climate, is the great Cueva, or Cavern of the Guacharo.* In a country where the people love the marvellous, a cavern which gives birth to a river, and is inhabited by thousands of nocturnal birds, the fat of which is employed in the Missions to dress food, is an everlasting object of conversation and discussion. The cavern, which the natives call “a mine of fat” is not in the valley of Caripe itself, but three short leagues distant from the convent, in the direction of west-south-west. It opens into a lateral valley, which terminates at the Sierra del Guacharo.
[* The province of Guacharucu, which Delgado visited in 1534, in the expedition of Hieronimo de Ortal, appears to have been situated south or south-east of Macarapana. Has its name any connexion with those of the cavern and the bird? or is this last of Spanish origin? (Laet Nova Orbis page 676). Guacharo means in Castilian “one who cries and laments;” now the bird of the cavern of Caripe, and the guacharaca (Phasianus parraka) are very noisy birds.]
We set out for the Sierra on the 18th of September, accompanied by the alcaldes, or Indian magistrates, and the greater part of the monks of the convent. A narrow path led us at first towards the south, across a fine plain, covered with beautiful turf. We then turned westward, along the margin of a small river which issues from the mouth of the cavern. We ascended during three quarters of an hour, sometimes in the water, which was shallow, sometimes between the torrent and a wall of rocks, on a soil extremely slippery and miry. The falling down of the earth, the scattered trunks of trees, over which the mules could scarcely pass, and the creeping plants that covered the ground, rendered this part of the road fatiguing. We were surprised to find here, at scarcely 500 toises above the level of the sea, a cruciferous plant, Raphanus pinnatus. Plants of this family are very rare in the tropics; they have in some sort a northern character, and therefore we never expected to see one on the plain of Caripe at so inconsiderable an elevation. The northern character also appears in the Galium caripense, the Valeriana scandens, and a sanicle not unlike the S. marilandica.
At the foot of the lofty mountain of the Guacharo, we were only four hundred paces from the cavern, without yet perceiving the entrance. The torrent runs in a crevice hollowed out by the waters, and we went on under a cornice, the projection of which prevented us from seeing the sky. The path winds in the direction of the river; and at the last turning we came suddenly before the immense opening of the grotto. The aspect of this spot is majestic, even to the eye of a traveller accustomed to the picturesque scenery of the higher Alps. I had before this seen the caverns of the peak of Derbyshire, where, lying down flat in a boat, we proceeded along a subterranean river, under an arch two feet high. I had visited the beautiful grotto of Treshemienshiz, in the Carpathian mountains, the caverns of the Hartz, and those of Franconia, which are vast cemeteries,* containing bones of tigers, hyenas, and bears, as large as our horses. Nature in every zone follows immutable laws in the distribution of rocks, in the form of mountains, and even in those changes which the exterior crust of our planet has undergone. So great a uniformity led me to believe that the aspect of the cavern of Caripe would differ little from what I had observed in my preceding travels. The reality far exceeded my expectations. If the configuration of the grottoes, the splendour of the stalactites, and all the phenomena of inorganic nature, present striking analogies, the majesty of equinoctial vegetation gives at the same time an individual character to the aperture of the cavern.
[* The mould, which has covered for thousands of years the soil of the caverns of Gaylenreuth and Muggendorf in Franconia, emits even now choke-damps, or gaseous mixtures of hydrogen and nitrogen, which rise to the roof of the caves. This fact is known to the persons who show these caverns to travellers; and when I was director of the mines of the Fichtelberg, I observed it frequently in the summer-time. M. Laugier found in the mould of Muggendorf, besides phosphate of lime, 0.10 of animal matter. I was struck, during my stay at Steeben, with the ammoniacal and fetid smell produced by it, when thrown on a red-hot iron.]
The Cueva del Guacharo is pierced in the vertical profile of a rock. The entrance is towards the south, and forms an arch eighty feet broad and seventy-two high. The rock which surmounts the grotto is covered with trees of gigantic height. The mammee-tree and the genipa,* with large and shining leaves, raise their branches vertically towards the sky; whilst those of the courbaril and the erythrina form, as they extend, a thick canopy of verdure. Plants of the family of pothos, with succulent stems, oxalises, and orchideae of a singular structure,* rise in the driest clefts of the rocks; while creeping plants waving in the winds are interwoven in festoons before the opening of the cavern. We distinguished in these festoons a bignonia of a violet blue, the purple dolichos, and for the first time, that magnificent solandra,* which has an orange-coloured flower and a fleshy tube more than four inches long.
[* Caruto, Genipa americana. The flower at Caripe, has sometimes five, sometimes six stamens.]
[* A dendrobium, with a gold-coloured flower, spotted with black, three inches long.]
[* Solandra scandens. It is the gousaticha of the Chayma Indians.]
But this luxury of vegetation embellishes not only the external arch, it appears even in the vestibule of the grotto. We saw with astonishment plantain-leaved heliconias eighteen feet high, the praga palm-tree, and arborescent arums, following the course of the river, even to those subterranean places. The vegetation continues in the cave of Caripe as in those deep crevices of the Andes, half-excluded from the light of day, and does not disappear till, penetrating into the interior, we advance thirty or forty paces from the entrance. We measured the way by means of a cord; and we went on about four hundred and thirty feet without being obliged to light our torches. Daylight penetrates far into this region, because the grotto forms but one single channel, keeping the same direction, from south-east to north-west. Where the light began to fail, we heard from afar the hoarse sounds of the nocturnal birds; sounds which the natives think belong exclusively to those subterraneous places.
The guacharo is of the size of our fowls. It has the mouth of the goat-suckers and procnias, and the port of those vultures whose crooked beaks are surrounded with stiff silky hairs. Suppressing, with M. Cuvier, the order of picae, we must refer this extraordinary bird to the passeres, the genera of which are connected with each other by almost imperceptible transitions. It forms a new genus, very different from the goatsucker, in the loudness of its voice, in the vast strength of its beak (containing a double tooth), and in its feet without the membranes which unite the anterior phalanges of the claws. It is the first example of a nocturnal bird among the Passeres dentirostrati. Its habits present analogies both with those of the goatsuckers and of the alpine crow.* The plumage of the guacharo is of a dark bluish grey, mixed with small streaks and specks of black. Large white spots of the form of a heart, and bordered with black, mark the head, wings, and tail. The eyes of the bird, which are dazzled by the light of day, are blue, and smaller than those of the goatsucker. The spread of the wings, which are composed of seventeen or eighteen quill feathers, is three feet and a half. The guacharo quits the cavern at nightfall, especially when the moon shines. It is almost the only frugiferous nocturnal bird yet known; the conformation of its feet sufficiently shows that it does not hunt like our owls. It feeds on very hard fruits, like the nutcracker* and the pyrrhocorax. The latter nestles also in clefts of rocks, and is known by the name of the night-crow. The Indians assured us that the guacharo does not pursue either the lamellicornous insects or those phalaenae which serve as food to the goatsuckers. A comparison of the beaks of the guacharo and the goatsucker serves to denote how much their habits must differ. It would be difficult to form an idea of the horrible noise occasioned by thousands of these birds in the dark part of the cavern. Their shrill and piercing cries strike upon the vaults of the rocks, and are repeated by the subterranean echoes. The Indians showed us the nests of the guacharos by fixing a torch to the end of a long pole. These nests were fifty or sixty feet high above our heads, in holes in the shape of funnels, with which the roof of the grotto is pierced like a sieve. The noise increased as we advanced, and the birds were scared by the light of the torches of copal. When this noise ceased a few minutes around us, we heard at a distance the plaintive cries of the birds roosting in other ramifications of the cavern. It seemed as if different groups answered each other alternately.
[* Corvus Pyrrhocorax.]
[* Corvus caryocatactes, C. glandarius. Our Alpine crow builds its nest near the top of Mount Libanus, in subterranean caverns, nearly like the guacharo. It also has the horribly shrill cry of the latter.]
The Indians enter the Cueva del Guacharo once a year, near midsummer. They go armed with poles, with which they destroy the greater part of the nests. At that season several thousand birds are killed; and the old ones, as if to defend their brood, hover over the heads of the Indians, uttering terrible cries. The young,* which fall to the ground, are opened on the spot. Their peritoneum is found extremely loaded with fat, and a layer of fat reaches from the abdomen to the anus, forming a kind of cushion between the legs of the bird. This quantity of fat in frugivorous animals, not exposed to the light, and exerting very little muscular motion, reminds us of what has been observed in the fattening of geese and oxen. It is well known how greatly darkness and repose favour this process. The nocturnal birds of Europe are lean, because, instead of feeding on fruits, like the guacharo, they live on the scanty produce of their prey. At the period commonly called, at Caripe, the oil harvest,* the Indians build huts with palm-leaves, near the entrance, and even in the porch of the cavern. There, with a fire of brushwood, they melt in pots of clay the fat of the young birds just killed. This fat is known by the name of butter or oil (manteca, or aceite) of the guacharo. It is half liquid, transparent, without smell, and so pure that it may be kept above a year without becoming rancid. At the convent of Caripe no other oil is used in the kitchen of the monks but that of the cavern; and we never observed that it gave the aliments a disagreeable taste or smell.
[* Called Los pollos del Guacharo.]
[* La cosecha de la manteca.]
The race of the guacharos would have been long ago extinct, had not several circumstances contributed to its preservation. The natives, restrained by their superstitious ideas, seldom have courage to penetrate far into the grotto. It appears also, that birds of the same species dwell in neighbouring caverns, which are too narrow to be accessible to man. Perhaps the great cavern is repeopled by colonies which forsake the small grottoes; for the missionaries assured us that hitherto no sensible diminution of the birds has been observed. Young guacharos have been sent to the port of Cumana, and have lived there several days without taking any nourishment, the seeds offered to them not suiting their taste. When the crops and gizzards of the young birds are opened in the cavern, they are found to contain all sorts of hard and dry fruits, which furnish, under the singular name of guacharo seed (semilla del guacharo), a very celebrated remedy against intermittent fevers. The old birds carry these seeds to their young. They are carefully collected, and sent to the sick at Cariaco, and other places of the low regions, where fevers are generally prevalent.
As we continued to advance into the cavern, we followed the banks of the small river which issues from it, and is from twenty-eight to thirty feet wide. We walked on the banks, as far as the hills formed of calcareous incrustations permitted us. Where the torrent winds among very high masses of stalactites, we were often obliged to descend into its bed, which is only two feet deep. We learned with surprise, that this subterranean rivulet is the origin of the river Caripe, which, at the distance of a few leagues, where it joins the small river of Santa Maria, is navigable for canoes. It flows into the river Areo under the name of Cano do Terezen. We found on the banks of the subterranean rivulet a great quantity of palm-tree wood, the remains of trunks, on which the Indians climb to reach the nests hanging from the roofs of the cavern. The rings, formed by the vestiges of the old footstalks of the leaves, furnish as it were the steps of a ladder perpendicularly placed.
The Grotto of Caripe preserves the same direction, the same breadth, and its primitive height of sixty or seventy feet, to the distance of 472 metres, or 1458 feet, accurately measured. We had great difficulty in persuading the Indians to pass beyond the anterior portion of the grotto, the only part which they annually visit to collect the fat. The whole authority of ‘los padres’ was necessary to induce them to advance as far as the spot where the soil rises abruptly at an inclination of sixty degrees, and where the torrent forms a small subterranean cascade.* The natives connect mystic ideas with this cave, inhabited by nocturnal birds; they believe that the souls of their ancestors sojourn in the deep recesses of the cavern. “Man,” say they, “should avoid places which are enlightened neither by the sun (zis), nor by the moon (nuna).” ‘To go and join the guacharos,’ is with them a phrase signifying to rejoin their fathers, to die. The magicians (piaches) and the poisoners (imorons) perform their nocturnal tricks at the entrance of the cavern, to conjure the chief of the evil spirits (ivorokiamo). Thus in every region of the earth a resemblance may be traced in the early fictions of nations, those especially which relate to two principles governing the world, the abode of souls after death, the happiness of the virtuous and the punishment of the guilty. The most different and most barbarous languages present a certain number of images, which are the same, because they have their source in the nature of our intelligence and our sensations. Darkness is everywhere connected with the idea of death. The Grotto of Caripe is the Tartarus of the Greeks; and the guacharos, which hover over the rivulet, uttering plaintive cries, remind us of the Stygian birds.
[* We find the phenomenon of a subterranean cascade, but on a much larger scale, in England, at Yordas Cave, near Kingsdale in Yorkshire.]
At the point where the river forms the subterranean cascade, a hill covered with vegetation, which is opposite to the opening of the grotto, presents a very picturesque aspect. It is seen at the extremity of a straight passage, 240 toises in length. The stalactites descending from the roof, and resembling columns suspended in the air, are relieved on a back-ground of verdure. The opening of the cavern appeared singularly contracted, when we saw it about the middle of the day, illumined by the vivid light reflected at once from the sky, the plants, and the rocks. The distant light of day formed a strange contrast with the darkness which surrounded us in the vast cavern. We discharged our guns at a venture, wherever the cries of the nocturnal birds and the flapping of their wings, led us to suspect that a great number of nests were crowded together. After several fruitless attempts M. Bonpland succeeded in killing a couple of guacharos, which, dazzled by the light of the torches, seemed to pursue us. This circumstance afforded me the means of making a drawing of this bird, which had previously been unknown to naturalists. We climbed, not without difficulty, the small hill whence the subterranean rivulet descends. We saw that the grotto was perceptibly contracted, retaining only forty feet in height, and that it continued stretching to north-east, without deviating from its primitive direction, which is parallel to that of the great valley of Caripe.
In this part of the cavern, the rivulet deposits a blackish mould, very like the matter which, in the grotto of Muggendorf, in Franconia, is called “the earth of sacrifice.”* We could not discover whether this fine and spongy mould falls through the cracks which communicate with the surface of the ground above, or is washed down by the rain-water penetrating into the cavern. It was a mixture of silex, alumina, and vegetable detritus. We walked in thick mud to a spot where we beheld with astonishment the progress of subterranean vegetation. The seeds which the birds carry into the grotto to feed their young, spring up wherever they fix in the mould which covers the calcareous incrustations. Blanched stalks, with some half-formed leaves, had risen to the height of two feet. It was impossible to ascertain the species of these plants, their form, colour, and aspect having been changed by the absence of light. These traces of organization amidst darkness forcibly excited the curiosity of the natives, who examined them with silent meditation inspired by a place they seemed to dread. They evidently regarded these subterranean plants, pale and deformed, as phantoms banished from the face of the earth. To me the scene recalled one of the happiest periods of my early youth, a long abode in the mines of Freyberg, where I made experiments on the effects of blanching (etiolement), which are very different, according as the air is pure or overcharged with hydrogen or azote.
[* Opfer-erde of the cavern of Hohle Berg (or Hole Mountain — a mountain pierced entirely through.)]
The missionaries, with all their authority, could not prevail on the Indians to penetrate farther into the cavern. As the roof became lower the cries of the guacharos were more and more shrill. We were obliged to yield to the pusillanimity of our guides, and trace back our steps. The appearance of the cavern was however very uniform. We found that a bishop of St. Thomas of Guiana had gone farther than ourselves. He had measured nearly 2500 feet from the mouth to the spot where he stopped, but the cavern extended still farther. The remembrance of this fact was preserved in the convent of Caripe, without the exact period being noted. The bishop had provided himself with great torches of white Castile wax. We had torches composed only of the bark of trees and native resin. The thick smoke which issued from these torches, in a narrow subterranean passage, hurts the eyes and obstructs the respiration.
On turning back to go out of the cavern, we followed the course of the torrent. Before our eyes became dazzled with the light of day we saw on the outside of the grotto the water of the river sparkling amid the foliage of the trees which shaded it. It was like a picture placed in the distance, the mouth of the cavern serving as a frame. Having at length reached the entrance, we seated ourselves on the bank of the rivulet, to rest after our fatigues. We were glad to be beyond the hoarse cries of the birds, and to leave a place where darkness does not offer even the charm of silence and tranquillity. We could scarcely persuade ourselves that the name of the Grotto of Caripe had hitherto been unknown in Europe;* for the guacharos alone might have sufficed to render it celebrated. These nocturnal birds have been no where yet discovered, except in the mountains of Caripe and Cumanacoa. The missionaries had prepared a repast at the entry of the cavern. Leaves of the banana and the vijao,* which have a silky lustre, served us as a table-cloth, according to the custom of the country. Nothing was wanting to our enjoyment, not even remembrances, which are so rare in those countries, where generations disappear without leaving a trace of their existence.
[* It is surprising that Father Gili, author of the Saggio di Storia Americana, does not mention it, though he had in his possession a manuscript written in 1780 at the convent of Caripe. I gave the first information respecting the Cueva del Guacharo in 1800, in my letters to Messrs. Delambre and Delametherie, published in the Journal de Physique.]
[* Heliconia bihai, Linn. The Creoles have changed the b of the Haitian word bihao into v, and the h into j, agreeably to the Castilian pronunciation.]
Before we quit the subterranean rivulet and the nocturnal birds, let us cast a last glance at the cavern of the Guacharo, and the whole of the physical phenomena it presents. When we have step by step pursued a long series of observations modified by the localities of a place, we love to stop and raise our views to general considerations. Do the great cavities, which are exclusively called caverns, owe their origin to the same causes as those which have produced the lodes of veins and of metalliferous strata, or the extraordinary phenomenon of the porosity of rocks? Do grottoes belong to every formation, or to that period only when organized beings began to people the surface of the globe? These geological questions can be solved only so far as they are directed by the actual state of things, that is, of facts susceptible of being verified by observation.
Considering rocks according to the succession of eras, we find that primitive formations exhibit very few caverns. The great cavities which are observed in the oldest granite, and which are called fours (ovens) in Switzerland and in the south of France, when they are lined with rock crystals, arise most frequently from the union of several contemporaneous veins of quartz,* of feldspar, or of fine-grained granite. The gneiss presents, though more seldom, the same phenomenon; and near Wunsiedel,* at the Fichtelgebirge, I had an opportunity of examining crystal fours of two or three feet diameter, in a part of the rock not traversed by veins. We are ignorant of the extent of the cavities which subterranean fires and volcanic agitations may have produced in the bowels of the earth in those primitive rocks, which, containing considerable quantities of amphibole, mica, garnet, magnetic iron-stone, and red schorl (titanite), appear to be anterior to granite. We find some fragments of these rocks among the matters ejected by volcanoes. The cavities can be considered only as partial and local phenomena; and their existence is scarcely any contradiction to the notions we have acquired from the experiments of Maskelyne and Cavendish on the mean density of the earth.
[* Gleichzeitige Trummer. To these stone veins which appear to be of the same age as the rock, belong the veins of talc and asbestos in serpentine, and those of quartz traversing schist (Thonschiefer). Jameson on Contemporaneous Veins, in the Mem. of the Wernerian Soc.]
[* In Franconia, south-east of Luchsburg.]
In the primitive mountains open to our researches, real grottoes, those which have some extent, belong only to calcareous formations, such as the carbonate or sulphate of lime. The solubility of these substances appears to have favoured the action of the subterranean waters for ages. The primitive limestone presents spacious caverns as well as transition limestone,* and that which is exclusively called secondary. If these caverns be less frequent in the first, it is because this stone forms in general only layers subordinate to the mica-slate,* and not a particular system of mountains, into which the waters may filter, and circulate to great distances. The erosions occasioned by this element depend not only on its quantity, but also on the length of time during which it remains, the velocity it acquires by its fall, and the degree of solubility of the rock. I have observed in general, that the waters act more easily on the carbonates and the sulphates of lime of secondary mountains than on the transition limestones, which have a considerable mixture of silex and carbon. On examining the internal structure of the stalactites which line the walls of caverns, we find in them all the characters of a chemical precipitate.
[* In the primitive limestone are found the Kuetzel-loch, near Kaufungen in Silesia, and probably several caverns in the islands of the Archipelago. In the transition limestone we remark the caverns of Elbingerode, of Rubeland, and of Scharzfeld, in the Hartz; those of the Salzfluhe in the Grisons; and, according to Mr. Greenough, that of Torbay in Devonshire.]
[* Sometimes to gneiss, as at the Simplon, between Dovredo and Crevola.]
As we approach those periods in which organic life develops itself in a greater number of forms, the phenomenon of grottoes becomes more frequent. There exist several under the name of baumen,* not in the ancient sandstone to which the great coal formation belongs, but in the Alpine limestone, and in the Jura limestone, which is often only the superior part of the Alpine formation. The Jura limestone* so abounds with caverns in both continents, that several geologists of the school of Freyberg have given it the name of cavern-limestone (hohlenkalkstein). It is this rock which so often interrupts the course of rivers, by engulfing them into its bosom. In this also is formed the famous Cueva del Guacharo, and the other grottoes of the valley of Caripe. The muriatiferous gypsum,* whether it be found in layers in the Jura or Alpine limestone, or whether it separate these two formations, or lie between the Alpine limestone and argillaceous sandstone, also presents, on account of its great solubility, enormous cavities, sometimes communicating with each other at several leagues distance. After the limestone and gypseous formations, there would remain to be examined, among the secondary rocks, a third formation, that of the argillaceous sandstone, newer than the brine-spring formations; but this rock, composed of small grains of quartz cemented by clay, seldom contains caverns; and when it does, they are not extensive. Progressively narrowing towards their extremity, their walls are covered with a brown ochre.
[* In the dialect of the German Swiss, Balmen. The Baumen of the Sentis, of the Mole, and of the Beatenberg, on the borders of the lake of Thun, belong to the Alpine limestone.]
[* I may mention only the grottoes of Boudry, Motiers–Travers, and Valorbe, in the Jura; the grotto of Balme near Geneva; the caverns between Muggendorf and Gaylenreuth in Franconia; Sowia Jama, Ogrodzimiec, and Wlodowice, in Poland.]
[* Gypsum of Bottendorf, schlottengyps.]
We have just seen, that the form of grottoes depends partly on the nature of the rocks in which they are found; but this form, modified by exterior agents, often varies even in the same formation. The configuration of caverns, like the outline of mountains, the sinuosity of valleys, and so many other phenomena, present at first sight only irregularity and confusion. The appearance of order is resumed, when we can extend our observations over a vast space of ground, which has undergone violent, but periodical and uniform revolutions. From what I have seen in the mountains of Europe, and in the Cordilleras of America, caverns may be divided, according to their interior structure, into three classes. Some have the form of large clefts or crevices, like veins not filled with ore; such as the cavern of Rosenmuller, in Franconia, Elden-hole, in the peak of Derbyshire, and the Sumideros of Chamacasapa in Mexico. Other caverns are open to the light at both ends. These are rocks really pierced; natural galleries, which run through a solitary mountain: such are the Hohleberg of Muggendorf, and the famous cavern called Dantoe by the Ottomite Indians, and the Bridge of the Mother of God, by the Mexican Spaniards. It is difficult to decide respecting the origin of these channels, which sometimes serve as beds for subterranean rivers. Are these pierced rocks hollowed out by the impulse of a current? or should we rather admit that one of the openings of the cavern is owing to a falling down of the earth subsequent to its original formation; to a change in the external form of the mountain, for instance, to a new valley opened on its flank? A third form of caverns, and the most common of the whole, exhibits a succession of cavities, placed nearly on the same level, running in the same direction, and communicating with each other by passages of greater or less breadth.
To these differences of general form are added other circumstances not less remarkable. It often happens, that grottoes of little space have extremely wide openings; whilst we have to creep under very low vaults, in order to penetrate into the deepest and most spacious caverns. The passages which unite partial grottoes, are generally horizontal. I have seen some, however, which resemble funnels or wells, and which may be attributed to the escape of some elastic fluid through a mass before being hardened. When rivers issue from grottoes, they form only a single, horizontal, continuous channel, the dilatations of which are almost imperceptible; as in the Cueva del Guacharo we have just described, and the cavern of San Felipe, near Tehuilotepec in the western Cordilleras of Mexico. The sudden disappearance* of the river, which took its rise from this last cavern, has impoverished a district in which farmers and miners equally require water for refreshing the soil and for working hydraulic machinery.
[* In the night of the 16th April, 1802.]
Considering the variety of structure exhibited by grottoes in both hemispheres, we cannot but refer their formation to causes totally different. When we speak of the origin of caverns we must choose between two systems of natural philosophy: one of these systems attributes every thing to instantaneous and violent commotions (for example, to the elastic force of vapours, and to the heavings occasioned by volcanoes); while the other rests on the operation of small powers, which produce effects almost insensibly by progressive action. Those who love to indulge in geological hypotheses must not, however, forget the horizontality so often remarked amidst gypseous and calcareous mountains, in the position of grottoes communicating with each other by passages. This almost perfect horizontality, this gentle and uniform slope, appears to be the result of a long abode of the waters, which enlarge by erosion clefts already existing, and carry off the softer parts the more easily, as clay or muriate of soda is found mixed with the gypsum and fetid limestone. These effects are the same, whether the caverns form one long and continued range, or several of these ranges lie one over another, as happens almost exclusively in gypseous mountains.
That which in shelly or Neptunean rocks is caused by the action of the waters, appears sometimes to be in the volcanic rocks the effect of gaseous emanations* acting in the direction where they find the least resistance. When melted matter moves on a very gentle slope, the great axis of the cavity formed by the elastic fluids is nearly horizontal, or parallel to the plane on which the movement of transition takes place. A similar disengagement of vapours, joined to the elastic force of the gases, which penetrate strata softened and raised up, appears sometimes to have given great extent to the caverns found in trachytes or trappean porphyries. These porphyritic caverns, in the Cordilleras of Quito and Peru, bear the Indian name of Machays.* They are in general of little depth. They are lined with sulphur, and differ by the enormous size of their openings from those observed in volcanic tufas* in Italy, at Teneriffe, and in the Andes. It is by connecting in the mind the primitive, secondary, and volcanic rocks, and distinguishing between the oxidated crust of the globe, and the interior nucleus, composed perhaps of metallic and inflammable substances, that we may account for the existence of grottoes everywhere. They act in the economy of nature as vast reservoirs of water and of elastic fluids.
[* At Vesuvius, the Duke de la Torre showed me, in 1805, in currents of recent lava, cavities extending in the direction of the current, six or seven feet long and three feet high. These little volcanic caverns were lined with specular iron, which cannot be called oligiste iron, since M. Gay–Lussac’s last experiments on the oxides of iron.]
[* Machay is a word of the Quichua language, commonly called by the Spaniards the Incas’ language. Callancamachay means a cavern as large as a house, a cavern that serves as a tambo or caravansarai.]
[*Sometimes fire acts like water in carrying off masses, and thus the cavities may be caused by an igneous, though more frequently by an aqueous erosion or solution.]
The gypseous caverns glitter with crystallized selenites. Vitreous crystallized plates of brown and yellow stand out on a striated ground composed of layers of alabaster and fetid limestone. The calcareous grottoes have a more uniform tint. They are more beautiful, and richer in stalactites, in proportion as they are narrower, and the circulation of air is less free. By being spacious, and accessible to air, the cavern of Caripe is almost destitute of those incrustations, the imitative forms of which are in other countries objects of popular curiosity. I also sought in vain for subterranean plants, those cryptogamia of the family of the Usneaceae, which we sometimes find fixed on the stalactites, like ivy on walls, when we penetrate for the first time into a lateral grotto.*
[* Lichen tophicola was discovered when the beautiful cavern of Rosenmuller in Franconia was first opened. The cavity containing the lichen was found closed on all sides by enormous masses of stalactite.]
The caverns in mountains of gypsum often contain mephitic emanations and deleterious gases. It is not the sulphate of lime that acts on the atmospheric air, but the clay slightly mixed with carbon, and the fetid limestone, so often mingled with the gypsum. We cannot yet decide, whether the swinestone acts as a hydrosulphuret, or by means of a bituminous principle.* Its property of absorbing oxygen gas is known to all the miners of Thuringia. It is the same as the action of the carburetted clay of the gypseous grottoes, and of the great chambers (sinkwerke) dug in mines of fossil salt which are worked by the introduction of fresh water. The caverns of calcareous mountains are not exposed to those decompositions of the atmospheric air, unless they contain bones of quadrupeds, or the mould mixed with animal gluten and phosphate of lime, from which arise inflammable and fetid gases.
[* That description of fetid limestone called by the German mineralogists stinkstein is always of a blackish brown colour. It is only by decomposition that it becomes white, after having acted on the surrounding air. The stinkstein which is of secondary formation, must not be confounded with a very white primitive granular limestone of the island of Thasos, which emits, when scraped, a smell of sulphuretted hydrogen. This marble is coarser grained than Carrara (Marmor lunense). It was frequently employed by the Grecian sculptors, and I often picked up fragments of it at the Villa Adriani, near Rome.]
Though we made many enquiries among the inhabitants of Caripe, Cumanacoa, and Cariaco, we did not learn that they had ever discovered in the cavern of Guacharo either the remains of carnivorous animals, or those bony breccias of herbivorous animals, which are found in the caverns of Germany and Hungary, and in the clefts of the calcareous rocks of Gibraltar. The fossil bones of the megatherium, of the elephant, and of the mastodon, which travellers have brought from South America, have all been found in the light soil of the valleys and table-lands. Excepting the megalonyx,* a kind of sloth of the size of an ox, described by Mr. Jefferson, I know not a single instance of the skeleton of an animal buried in a cavern of the New World. The extreme scarcity of this geological phenomenon will appear the less surprising to us, if we recollect, that in France, England, and Italy, there are also a great number of grottoes in which we have never met with any vestige of fossil bones.
[* The megalonyx was found in the caverns of Green Briar, in Virginia, at the distance of 1500 leagues from the megatherium, which resembles it very much, and is of the size of the rhinoceros.]
Although, in primitive nature, whatever relates to ideas of extent and mass is of no great importance, yet I may observe, that the cavern of Caripe is one of the most spacious known to exist in limestone formations. It is at least 900 metres or 2800 feet in length.* Owing to the different degrees of solubility in rocks, it is generally not in calcareous mountains, but in gypseous formations, that we find the most extensive succession of grottoes. In Saxony there are some in gypsum several leagues in length; for instance, that of Wimelburg, which communicates with the cavern of Cresfield.
[* The famous Baumannshohle in the Hartz, according to Messrs. Gilbert and Ilsen, is only 578 feet in length; the cavern of Scharzfeld 350; that of Gaylenreuth 304; that of Antiparos 300. But according to Saussure, the Grotto of Balme is 1300 feet.]
The determination of the temperature of grottoes presents a field for interesting observation. The cavern of Caripe, situated nearly in the latitude of 10° 10′, consequently in the centre of the torrid zone, is elevated 506 toises above the level of the sea in the gulf of Cariaco. We found that, in every part of it, in the month of September, the temperature of the internal air was between 18.4 and 18.9° of the centesimal thermometer; the external atmosphere being at 16.2°. At the entrance of the cavern, the thermometer in the open air was at 17.6°; but when immersed in the water of the little subterranean river, it marked, even to the end of the cavern, 16.8°. These experiments are very interesting, if we reflect on the tendency to equilibrium of heat, in the waters, the air, and the earth. When I left Europe, men of science were regretting that they had not sufficient data on what is called the temperature of the interior of the globe; and it is but very recently that efforts have been made, and with some success, to solve the grand problem of subterranean meteorology. The stony strata that form the crust of our planet, are alone accessible to our examination; and we now know that the mean temperature of these strata varies not only with latitudes and heights, but that, according to the position of the several places, it performs also, in the space of a year, regular oscillations round the mean heat of the neighbouring atmosphere. The time is gone by when men were surprised to find, in other zones, the heat of grottoes and wells differing from that observed in the caves of the observatory at Paris. The same instrument which in those caves marks 12°, rises in the subterraneous caverns of the island of Madeira, near Funchal, to 16.2°; in Joseph’s Well, at Cairo* to 21.2°; in the grottoes of the island of Cuba to 22 or 23°.* This increase is nearly in proportion to that of the mean temperature of the atmosphere, from latitude 48° to the tropics.
[* At Funchal (latitude 32° 37′) the mean temperature of the air is 20.4°, and at Cairo (latitude 30° 2′), according to Nouet, it is 22.4°.]
[* The mean temperature of the air at the Havannah, according to Mr. Ferrer, is 25.6°.]
We have just seen that, in the Cueva del Guacharo, the water of the river is nearly 2° colder than the ambient air of the cavern. The water, whether in filtering through the rocks, or in running over stony beds, doubtless imbibes the temperature of these beds. The air contained in the grotto, on the contrary, is not in repose; it communicates with the external atmosphere. Though under the torrid zone, the changes of the external temperature are exceedingly trifling, currents are formed, which modify periodically the internal air. It is consequently the temperature of the waters, that of 16.8°, which we might look upon as the temperature of the earth in those mountains, if we were sure that the waters do not descend rapidly from more elevated neighbouring mountains.
It follows from these observations, that when we cannot obtain results perfectly exact, we find at least under each zone certain numbers which indicate the maximum and minimum. At Caripe, in the equinoctial zone, at an elevation of 500 toises, the mean temperature of the globe is not below 16.8°, which was the degree indicated by the water of the subterranean river. We can even prove that this temperature of the globe is not above 19°, since the air of the cavern, in the month of September, was found to be at 18.7°. As the mean temperature of the atmosphere, in the hottest month, does not exceed 19.5°,* it is probable that a thermometer in the grotto would not rise higher than 19° at any season of the year.
[* The mean temperature of the month of September at Caripe is 18.5°; and on the coast of Cumana, where we had opportunities of making numerous observations, the mean heat of the warmest months differs only 1.8° from that of the coldest.]
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