Volume I Part 15 (1/2)
That which in sh.e.l.ly 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. (* 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.) 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.* (* 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.) 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. (*Sometimes fire acts like water in carrying off ma.s.ses, and thus the cavities may be caused by an igneous, though more frequently by an aqueous erosion or solution.) It is by connecting in the mind the primitive, secondary, and volcanic rocks, and distinguis.h.i.+ng 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.
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 stalact.i.tes, in proportion as they are narrower, and the circulation of air is less free. By being s.p.a.cious, and accessible to air, the cavern of Caripe is almost dest.i.tute 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 stalact.i.tes, 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 ma.s.ses of stalact.i.te.)
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.* (* 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 sc.r.a.ped, a smell of sulphuretted hydrogen. This marble is coa.r.s.er 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.) 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.
Though we made many enquiries among the inhabitants of Caripe, c.u.manacoa, 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 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.) 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.
Although, in primitive nature, whatever relates to ideas of extent and ma.s.s is of no great importance, yet I may observe, that the cavern of Caripe is one of the most s.p.a.cious known to exist in limestone formations. It is at least 900 metres or 2800 feet in length.* (* 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.) 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 determination of the temperature of grottoes presents a field for interesting observation. The cavern of Caripe, situated nearly in the lat.i.tude of 10 degrees 10 minutes, 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 degrees of the centesimal thermometer; the external atmosphere being at 16.2 degrees. At the entrance of the cavern, the thermometer in the open air was at 17.6 degrees; but when immersed in the water of the little subterranean river, it marked, even to the end of the cavern, 16.8 degrees. 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 lat.i.tudes and heights, but that, according to the position of the several places, it performs also, in the s.p.a.ce 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 degrees, rises in the subterraneous caverns of the island of Madeira, near Funchal, to 16.2 degrees; in Joseph's Well, at Cairo* to 21.2 degrees (* At Funchal (lat.i.tude 32 degrees 37 minutes) the mean temperature of the air is 20.4 degrees, and at Cairo (lat.i.tude 30 degrees 2 minutes), according to Nouet, it is 22.4 degrees.); in the grottoes of the island of Cuba to 22 or 23 degrees.* (* The mean temperature of the air at the Havannah, according to Mr. Ferrer, is 25.6 degrees.) This increase is nearly in proportion to that of the mean temperature of the atmosphere, from lat.i.tude 48 degrees to the tropics.
We have just seen that, in the Cueva del Guacharo, the water of the river is nearly 2 degrees 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 degrees, 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 degrees, 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 degrees, since the air of the cavern, in the month of September, was found to be at 18.7 degrees. As the mean temperature of the atmosphere, in the hottest month, does not exceed 19.5 degrees,* it is probable that a thermometer in the grotto would not rise higher than 19 degrees at any season of the year. (* The mean temperature of the month of September at Caripe is 18.5 degrees; and on the coast of c.u.mana, where we had opportunities of making numerous observations, the mean heat of the warmest months differs only 1.8 degrees from that of the coldest.)
CHAPTER 1.8.
DEPARTURE FROM CARIPE.
MOUNTAIN AND FOREST OF SANTA MARIA.
MISSION OF CATUARO.
PORT OF CARIACO.
The days we pa.s.sed at the Capuchin convent in the mountains of Caripe, glided swiftly away, though our manner of living was simple and uniform. From sunrise to nightfall we traversed the forests and neighbouring mountains, to collect plants. When the winter rains prevented us from undertaking distant excursions, we visited the huts of the Indians, the conuco of the community, or those a.s.semblies in which the alcaldes every evening arrange the labours of the succeeding day. We returned to the monastery only when the sound of the bell called us to the refectory to share the repasts of the missionaries. Sometimes, very early in the morning, we followed them to the church, to attend the doctrina, that is to say, the religious instruction of the Indians. It was rather a difficult task to explain dogmas to the neophytes, especially those who had but a very imperfect knowledge of the Spanish language. On the other hand, the monks are as yet almost totally ignorant of the language of the Chaymas; and the resemblance of sounds confuses the poor Indians and suggests to them the most whimsical ideas. Of this I may cite an example. I saw a missionary labouring earnestly to prove that infierno, h.e.l.l, and invierno, winter, were not one and the same thing; but as different as heat and cold. The Chaymas are acquainted with no other winter than the season of rains; and consequently they imagined the h.e.l.l of the whites to be a place where the wicked are exposed to frequent showers. The missionary harangued to no purpose: it was impossible to efface the first impression produced by the a.n.a.logy between the two consonants. He could not separate in the minds of the neophytes the ideas of rain and h.e.l.l; invierno and infierno.
After pa.s.sing almost the whole day in the open air, we employed our evenings, at the convent, in making notes, drying our plants, and sketching those that appeared to form new genera. Unfortunately the misty atmosphere of a valley, where the surrounding forests fill the air with an enormous quant.i.ty of vapour, was unfavourable to astronomical observations. I spent a part of the nights waiting to take advantage of the moment when some star should be visible between the clouds, near its pa.s.sage over the meridian. I often s.h.i.+vered with cold, though the thermometer only sunk to 16 degrees, which is the temperature of the day in our climates towards the end of September. The instruments remained set up in the court of the convent for several hours, yet I was almost always disappointed in my expectations. Some good observations of Fomalhaut and of Deneb have given 10 degrees 10 minutes 14 seconds as the lat.i.tude of Caripe; which proves that the position indicated in the maps of Caulin is 18 minutes wrong, and in that of Arrowsmith 14 minutes.
Observations of corresponding alt.i.tudes of the sun having given me the true time, within about 2 seconds, I was enabled to determine the magnetic variation with precision, at noon. It was, on the 20th of September, 1799, 3 degrees 15 minutes 30 seconds north-east; consequently 0 degrees 58 minutes 15 seconds less than at c.u.mana.
If we attend to the influence of the horary variations, which in these countries do not in general exceed 8 minutes, we shall find, that at considerable distances the variation changes less rapidly than is usually supposed. The dip of the needle was 42.75 degrees, centesimal division, and the number of oscillations, expressing the intensity of the magnetic forces, rose to 229 in ten minutes.
The vexation of seeing the stars disappear in a misty sky was the only disappointment we felt in the valley of Caripe. The aspect of this spot presents a character at once wild and tranquil, gloomy and attractive. In the solitude of these mountains we are perhaps less struck by the new impressions we receive at every step, than with the marks of resemblance we trace in climates the most remote from each other. The hills by which the convent is backed, are crowned with palm-trees and arborescent ferns. In the evenings, when the sky denotes rain, the air resounds with the monotonous howling of the alouate apes, which resembles the distant sound of wind when it shakes the forest. Yet amid these strange sounds, these wild forms of plants, and these prodigies of a new world, nature everywhere speaks to man in a voice familiar to him. The turf that overspreads the soil: the old moss and fern that cover the roots of the trees; the torrents that gush down the sloping banks of the calcareous rocks; in fine, the harmonious accordance of tints reflected by the waters, the verdure, and the sky; everything recalls to the traveller, sensations which he has already felt.
The beauties of this mountain scenery so much engaged us, that we were very tardy in observing the embarra.s.sment felt by our kind entertainers the monks. They had but a slender provision of wine and wheaten bread; and although in those high regions both are considered as belonging merely to the luxuries of the table, yet we saw with regret, that our hosts abstained from them on our account.
Our portion of bread had already been diminished three-fourths, yet violent rains still obliged us to delay our departure for two days.
How long did this delay appear! It made us dread the sound of the bell that summoned us to the refectory.
We departed at length on the 22nd of September, followed by four mules, laden with our instruments and plants. We had to descend the north-east slope of the calcareous Alps of New Andalusia, which we have called the great chain of the Brigantine and the Cocollar. The mean elevation of this chain scarcely exceeds six or seven hundred toises: in respect to height and geological const.i.tution, we may compare it to the chain of the Jura. Notwithstanding the inconsiderable elevation of the mountains of c.u.mana, the descent is extremely difficult and dangerous in the direction of Cariaco. The Cerro of Santa Maria, which the missionaries ascend in their journey from c.u.mana to their convent at Caripe, is famous for the difficulties it presents to travellers. On comparing these mountains with the Andes of Peru, the Pyrenees, and the Alps, which we successively visited, it has more than once occurred to us, that the less lofty summits are sometimes the most inaccessible.
On leaving the valley of Caripe, we first crossed a ridge of hills north-east of the convent. The road led us along a continual ascent through a vast savannah, as far as the table-land of Guardia de San Augustin. We there halted to wait for the Indian who carried the barometer. We found ourselves to be at 533 toises of absolute elevation, or a little higher than the bottom of the cavern of Guacharo. The savannahs or natural meadows, which yield excellent pasture for the cows of the convent, are totally devoid of trees or shrubs. It is the domain of the monocotyledonous plants; for amidst the gramina only a few Maguey* plants rise here and there (* Agave Americana.); their flowery stalks being more than twenty-six feet high. Having reached the table-land of Guardia, we appeared to be transported to the bed of an old lake, levelled by the long-continued abode of the waters. We seemed to trace the sinuosities of the ancient sh.o.r.e in the tongues of land which jut out from the craggy rock, and even in the distribution of the vegetation. The bottom of the basin is a savannah, while its banks are covered with trees of full growth. This is probably the most elevated valley in the provinces of Venezuela and c.u.mana. One cannot but regret, that a spot favoured by so temperate a climate, and which without doubt would be fit for the culture of corn, is totally uninhabited.
From the table-land of Guardia we continued to descend, till we reached the Indian village of Santa Cruz. We pa.s.sed at first along a slope extremely slippery and steep, to which the missionaries had given the name of Baxada del Purgatorio, or Descent of Purgatory.
It is a rock of schistose sandstone, decomposed, covered with clay, the talus of which appears frightfully steep, from the effect of a very common optical illusion. When we look down from the top to the bottom of the hill the road seems inclined more than 60 degrees.
The mules in going down draw their hind legs near to their fore legs, and lowering their cruppers, let themselves slide at a venture. The rider runs no risk, provided he slacken the bridle, thereby leaving the animal quite free in his movements. From this point we perceived towards the left the great pyramid of Guacharo.
The appearance of this calcareous peak is very picturesque, but we soon lost sight of it, on entering the thick forest, known by the name of the Montana de Santa Maria. We descended without intermission for seven hours. It is difficult to conceive a more tremendous descent; it is absolutely a road of steps, a kind of ravine, in which, during the rainy season, impetuous torrents dash from rock to rock. The steps are from two to three feet high, and the beasts of burden, after measuring with their eyes the s.p.a.ce necessary to let their load pa.s.s between the trunks of the trees, leap from one rock to another. Afraid of missing their mark, we saw them stop a few minutes to scan the ground, and bring together their four feet like wild goats. If the animal does not reach the nearest block of stone, he sinks half his depth into the soft ochreous clay, that fills up the interstices of the rock. When the blocks are wanting, enormous roots serve as supports for the feet of men and beasts. Some of these roots are twenty inches thick, and they often branch out from the trunks of the trees much above the level of the soil. The Creoles have sufficient confidence in the address and instinct of the mules, to remain in their saddles during this long and dangerous descent. Fearing fatigue less than they did, and being accustomed to travel slowly for the purpose of gathering plants and examining the nature of the rocks, we preferred going down on foot; and, indeed, the care which our chronometers demanded, left us no liberty of choice.
The forest that covers the steep flank of the mountain of Santa Maria, is one of the thickest I ever saw. The trees are of stupendous height and size. Under their bushy, deep green foliage, there reigns continually a kind of dim daylight, a peculiar sort of obscurity, of which our forests of pines, oaks, and beech-trees, convey no idea. Notwithstanding its elevated temperature, it is difficult to believe that the air can dissolve the quant.i.ty of water exhaled from the surface of the soil, the foliage of the trees, and their trunks: the latter are covered with a drapery of orchideae, peperomia, and other succulent plants. With the aromatic odour of the flowers, the fruit, and even the wood, is mingled that which we perceive in autumn in misty weather. Here, as in the forests of the Orinoco, fixing our eyes on the top of the trees, we discerned streams of vapour, whenever a solar ray penetrated, and traversed the dense atmosphere. Our guides pointed out to us among those majestic trees, the height of which exceeded 120 or 130 feet, the curucay of Terecen. It yields a whitish liquid, and very odoriferous resin, which was formerly employed by the c.u.managoto and Tagiri Indians, to perfume their idols. The young branches have an agreeable taste, though somewhat astringent. Next to the curucay and enormous trunks of hymenaea, (the diameter of which was more than nine or ten feet), the trees which most excited our attention were the dragon's blood (Croton sanguifluum), the purple-brown juice of which flows down a whitish bark; the calahuala fern, different from that of Peru, but almost equally medicinal;* (* The calahuala of Caripe is the Polypodium cra.s.sifolium; that of Peru, the use of which has been so much extended by Messrs. Ruiz and Pavon, comes from the Aspidium coriaceum, Willd. (Tectaria calahuala, Cav.) In commerce the diaph.o.r.etic roots of the Polypodium cra.s.sifolium, and of the Acrostichum huascaro, are mixed with those of the calahuala or Aspidium coriaceum.) and the palm-trees, ira.s.se, macanilla, corozo, and praga.* (* Aiphanes praga.) The last yields a very savoury palm-cabbage, which we had sometimes eaten at the convent of Caripe. These palms with pinnated and th.o.r.n.y leaves formed a pleasing contrast to the fern-trees. One of the latter, the Cyathea speciosa,* grows to the height of more than thirty-five feet, a prodigious size for plants of this family.