0 : 2040 : 3976 : 2460 : 4794 : 420 : 818 : 27 : 21.6.
20 : 1550 : 3020 : 2360 : 4598 : 810 : 1578 : 24.5 : 19.6.
40 : 0 : 0 : 1540 : 3001 : 1540 : 3001 : 17 : 13.6.
This table presents only the ordinary state of nature, that is to say, the phenomena as they are annually observed. Exceptions founded on particular local circ.u.mstances, exist. Thus it sometimes snows, though seldom, at Naples, at Lisbon, and even at Malaga, consequently as low as the 37th degree of lat.i.tude: and, as we have just observed, snow has been seen to fall at Mexico, the elevation of which is 1173 toises above the level of the ocean. This phenomenon, which had not been seen for several centuries, took place on the day that the Jesuits were expelled, and was attributed by the people to that act of severity. A more striking exception was found in the climate of Valladolid, the capital of the province of Mechoacan. According to my measures, the height of this town, situate in lat.i.tude 19 degrees 42 minutes, is only a thousand toises: and yet, a few years before our arrival in New Spain, the streets were covered with snow for some hours.
Snow had been seen to fall also at Teneriffe, in a place lying above Esperanza de la Laguna, very near the town of that name, in the gardens of which the artocarpus flourishes. This extraordinary fact was confirmed to M. Broussonnet by very aged persons. The Erica arborea, the Myrica Faya, and the Arbutus callicarpa,* (*
This fine arbutus, imported by M. Broussonnet, is very different from the Arbutus laurifolia, with which it has been confounded, but which belongs to North America.) did not suffer from the snow; but it destroyed all the vines in the open air. This observation is interesting to vegetable physiology. In hot countries, the plants are so vigorous, that cold is less injurious to them, provided it be of short duration. I have seen the banana cultivated in the island of Cuba, in places where the thermometer descends to seven centesimal degrees, and sometimes very near freezing point. In Italy and Spain the orange and date-trees do not perish, though the cold during the night may be two degrees below freezing point. In general it is remarked by cultivators, that the trees which grow in a fertile soil are less delicate, and consequently less affected by great changes in the temperature, than those which grow in land that affords but little nutriment.* (* The mulberries, cultivated in the thin and sandy soils of countries bordering on the Baltic Sea, are examples of this feebleness of organization. The late frosts do more injury to them, than to the mulberries of Piedmont.
In Italy a cold of 5 degrees below freezing point does not destroy robust orange trees. According to M. Galesio, these trees, less tender than the lemon and bergamot orange trees, freeze only at ten centesimal degrees below freezing point.)
In order to pa.s.s from the town of Laguna to the port of Orotava and the western coast of Teneriffe, we cross at first a hilly region covered with black and argillaceous earth, in which are found some small crystals of pyroxene. The waters most probably detach these crystals from the neighbouring rocks, as at Frascati, near Rome.
Unfortunately, strata of ferruginous earth conceal the soil from the researches of the geologist. It is only in some ravines, that we find columnar basalts, somewhat curved, and above them very recent breccia, resembling volcanic tufa. The breccia contain fragments of the same basalts which they cover; and it is a.s.serted that marine petrifactions are observed in them. The same phenomenon occurs in the Vicentin, near Montechio Maggiore.
The valley of Tacoronte is the entrance into that charming country, of which travellers of every nation have spoken with rapturous enthusiasm. Under the torrid zone I found sites where nature is more majestic, and richer in the display of organic forms; but after having traversed the banks of the Orinoco, the Cordilleras of Peru, and the most beautiful valleys of Mexico, I own that I have never beheld a prospect more varied, more attractive, more harmonious in the distribution of the ma.s.ses of verdure and of rocks, than the western coast of Teneriffe.
The sea-coast is lined with date and cocoa trees. Groups of the musa, as the country rises, form a pleasing contrast with the dragon-tree, the trunks of which have been justly compared to the tortuous form of the serpent. The declivities are covered with vines, which throw their branches over towering poles. Orange trees loaded with flowers, myrtles, and cypress trees encircle the chapels reared to devotion on the isolated hills. The divisions of landed property are marked by hedges formed of the agave and the cactus. An innumerable quant.i.ty of cryptogamous plants, among which ferns are the most predominant, cover the walls, and are moistened by small springs of limpid water. In winter, when the volcano is buried under ice and snow, this district enjoys perpetual spring.
In summer, as the day declines, the breezes from the sea diffuse a delicious freshness. The population of this coast is very considerable; and it appears to be still greater than it is, because the houses and gardens are distant from each other, which adds to the picturesque beauty of the scene. Unhappily the real welfare of the inhabitants does not correspond with the exertions of their industry, or with the advantages which nature has lavished on this spot. The farmers are not land-owners; the fruits of their labour belong to the n.o.bles; and those feudal inst.i.tutions, which, for so long a time, spread misery throughout Europe, still press heavily on the people of the Canary Islands.
From Tegueste and Tacoronte to the village of St. Juan de la Rambla (which is celebrated for its excellent malmsey wine), the rising hills are cultivated like a garden. I might compare them to the environs of Capua and Valentia, if the western part of Teneriffe was not infinitely more beautiful on account of the proximity of the peak, which presents on every side a new point of view. The aspect of this mountain is interesting not merely from its gigantic ma.s.s; it excites the mind, by carrying it back to the mysterious source of its volcanic agency. For thousands of years, no flames or light have been perceived on the summit of the Piton, nevertheless enormous lateral eruptions, the last of which took place in 1798, are proofs of the activity of a fire still far from being extinguished. There is also something that leaves a melancholy impression on beholding a crater in the centre of a fertile and well cultivated country. The history of the globe informs us, that volcanoes destroy what they have been a long series of ages in creating. Islands, which the action of submarine fires has raised above the waters, are by degrees clothed in rich and smiling verdure; but these new lands are often laid waste by the renewed action of the same power which caused them to emerge from the bottom of the ocean. Islets, which are now but heaps of scoriae and volcanic ashes, were once perhaps as fertile as the hills of Tacoronte and Sauzal. Happy the country, where man has no distrust of the soil on which he lives!
Pursuing our course to the port of Orotava, we pa.s.sed the smiling hamlets of Matanza and Victoria. These names are mingled together in all the Spanish colonies, and they form an unpleasing contrast with the peaceful and tranquil feelings which those countries inspire. Matanza signifies slaughter, or carnage; and the word alone recalls the price at which victory has been purchased. In the New World it generally indicates the defeat of the natives: at Teneriffe, the village of Matanza was built in a place* (* The ancient Acantejo.) where the Spaniards were conquered by those same Guanches who soon after were sold as slaves in the markets of Europe.
Before we reached Orotava, we visited a botanic garden at a little distance from the port. We there found M. Le Gros, the French vice-consul, who had often scaled the summit of the Peak, and who served us as an excellent guide. He was accompanying captain Baudin in a voyage to the West Indies, when a dreadful tempest, of which M. Le Dru has given an account in the narrative of his voyage to Porto Rico, forced the vessel to put into Teneriffe. There M. Le Gros was led by the beauty of the spot to settle. It was he who augmented scientific knowledge by the first accurate ideas of the great lateral eruption of the Peak, which has been very improperly called the explosion of the volcano of Chahorra. This eruption took place on the 8th of June, 1798.
The establishment of a botanical garden at Teneriffe is a very happy idea, on account of the influence it is likely to have on the progress of botany, and on the introduction of useful plants into Europe. For the first conception of it we are indebted to the Marquis de Nava. He undertook, at an enormous expense, to level the hill of Durasno, which rises as an amphitheatre, and which was begun to be planted in 1795. The marquis thought that the Canary Islands, from the mildness of their climate and geographical position, were the most suitable place for naturalising the productions of the East and West Indies, and for inuring the plants gradually to the colder temperature of the south of Europe. The plants of Asia, Africa, and South America, may easily be brought to Orotava; and in order to introduce the bark-tree* into Sicily, Portugal, or Grenada, it should be first planted at Durasno, or at Laguna, and the shoots of this tree may afterwards be transported into Europe from the Canaries. (* I speak of the species of bark-tree (cinchona), which at Peru, and in the kingdom of New Granada, flourish on the back of the Cordilleras, at the height of between 1000 and 1500 toises, in places where the thermometer is between nine and ten degrees during the day, and from three to four during the night. The orange bark-tree (Cinchona lancifolia) is much less delicate than the red bark-tree (C. oblongifolia).) In happier times, when maritime wars shall no longer interrupt communication, the garden of Teneriffe may become extremely useful with respect to the great number of plants which are sent from the Indies to Europe; for ere they reach our coasts, they often perish, owing to the length of the pa.s.sage, during which they inhale an air impregnated with salt water. These plants would meet at Orotava with the care and climate necessary for their preservation. At Durasno, the protea, the psidium, the jambos, the chirimoya of Peru,* (* Annona cherimolia. Lamarck.) the sensitive plant, and the heliconia, grow in the open air. We gathered the ripened seeds of several beautiful species of glycine from New Holland, which the governor of c.u.mana, Mr. Emparan, had successfully cultivated, and which grow wild on the coasts of South America.
We arrived very late at the port of Orotava,* (* Puerto de la Cruz.
The only fine port of the Canary Islands is that of St. Sebastian, in the isle of Gomara.) if we may give the name of port to a road in which vessels are obliged to put to sea whenever the winds blow violently from the north-west. It is impossible to speak of Orotava without recalling to the remembrance of the friends of science the name of Don Bernardo Cologan, whose house at all times was open to travellers of every nation.
We could have wished to have sojourned for some time in Don Bernardo"s house, and to have visited with him the charming scenery of St. Juan de la Rambla and of Rialexo de Abaxo.* (* This last-named village stands at the foot of the lofty mountain of Tygayga.) But on a voyage such as we had undertaken, the present is but little enjoyed. Continually haunted by the fear of not executing the designs of the morrow, we live in perpetual uneasiness. Persons who are pa.s.sionately fond of nature and the arts feel the same sensations, when they travel through Switzerland and Italy. Enabled to see but a small portion of the objects which allure them, they are disturbed in their enjoyments by the restraints they impose on themselves at every step.
On the morning of the 21st of June, we were on our way to the summit of the volcano. M. Le Gros, whose attentions were unwearied, M. Lalande, secretary to the French Consulate at Santa Cruz, and the English gardener at Durasno, joined us on this excursion. The day was not very fine, and the summit of the peak, which is generally visible at Orotava from sunrise till ten o"clock, was covered with thick clouds.
We were agreeably surprised by the contrast between the vegetation of this part of Teneriffe, and that of the environs of Santa Cruz.
Under the influence of a cool and humid climate, the ground was covered with beautiful verdure; while on the road from Santa Cruz to Laguna the plants exhibited nothing but capsules emptied of their seeds. Near the port of Santa Cruz, the strength of the vegetation is an obstacle to geological research. We pa.s.sed along the base of two small hills, which rise in the form of bells.
Observations made at Vesuvius and in Auvergne lead us to think that these hills owe their origin to lateral eruptions of the great volcano. The hill called Montanita de la Villa seems indeed to have emitted lavas; and according to the tradition of the Guanches, an eruption took place in 1430. Colonel Franqui a.s.sured Borda, that the place is still to be seen whence the melted matter issued; and that the ashes which covered the ground adjacent, were not yet fertilized. Whenever the rock appeared, we discovered basaltic amygdaloid* (* Basaltartiger Mandelstein. Werner.) covered with hardened clay,* (* Bimstein-Conglomerat. W.) which contains rapilli, or fragments of pumice-stone. This last formation resembles the tufas of Pausilippo, and the strata of puzzolana, which I found in the valley of Quito, at the foot of the volcano of Pichincha. The amygdaloid has very long pores, like the superior strata of the lavas of Vesuvius, arising probably from the action of an elastic fluid forcing its way through the matter in fusion.
Notwithstanding these a.n.a.logies, I must here repeat, that in all the low region of the peak of Teneriffe, on the side of Orotava, I have met with no flow of lava, nor any current, the limits of which are strongly marked. Torrents and inundations change the surface of the globe, and when a great number of currents of lava meet and spread over a plain, as I have seen at Vesuvius, in the Atrio dei Cavalli, they seem to be confounded together, and wear the appearance of real strata.
The villa de Orotava has a pleasant aspect at a distance, from the great abundance of water which runs through the princ.i.p.al streets.
The spring of Agua Mansa, collected in two large reservoirs, turns several mills, and is afterward discharged among the vineyards of the adjacent hills. The climate is still more refreshing at the villa than at the port of La Cruz, from the influence of the breeze, which blows strong after ten in the morning. The water, which has been dissolved in the air at a higher temperature, frequently precipitates itself; and renders the climate very foggy.
The villa is nearly 160 toises (312 metres) above the level of the sea, consequently 200 toises lower than the site on which Laguna is built: it is observed also, that the same kind of plants flower a month later in this latter place.
Orotava, the ancient Taoro of the Guanches, is situated on a very steep declivity. The streets seem deserted; the houses are solidly built, and of a gloomy appearance. We pa.s.sed along a lofty aqueduct, lined with a great number of fine ferns; and visited several gardens, in which the fruit trees of the north of Europe are mingled with orange trees, pomegranate, and date trees. We were a.s.sured, that these last were as little productive here as on the coast of c.u.mana. Although we had been made acquainted, from the narratives of many travellers, with the dragon-tree of the garden of M. Franqui, we were not the less struck with its enormous magnitude. We were told, that the trunk of this tree, which is mentioned in several very ancient doc.u.ments as marking the boundaries of a field, was as gigantic in the fifteenth century as it is at the present time. Its height appeared to us to be about 50 or 60 feet; its circ.u.mference near the roots is 45 feet. We could not measure higher, but Sir George Staunton found that, 10 feet from the ground, the diameter of the trunk is still 12 English feet; which corresponds perfectly with the statement of Borda, who found its mean circ.u.mference 33 feet 8 inches, French measure. The trunk is divided into a great number of branches, which rise in the form of a candelabrum, and are terminated by tufts of leaves, like the yucca which adorns the valley of Mexico. This division gives it a very different appearance from that of the palm-tree.
Among organic creations, this tree is undoubtedly, together with the Adansonia or baobab of Senegal, one of the oldest inhabitants of our globe. The baobabs are of still greater dimensions than the dragon-tree of Orotava. There are some which near the root measure 34 feet in diameter, though their total height is only from 50 to 60 feet. But we should observe, that the Adansonia, like the ochroma, and all the plants of the family of bombax, grow much more rapidly* than the dracaena, the vegetation of which is very slow.
(* It is the same with the plane-tree (Plata.n.u.s occidentalis) which M. Michaux measured at Marietta, on the banks of the Ohio, and which, at twenty feet from the ground, was 15.7 feet in diameter.
--"Voyage a l"Ouest des Monts Alleghany" 1804 page 93. The yew, chestnut, oak, plane-tree, deciduous cypress, bombax, mimosa, caesalpina, hymenaea, and dracaena, appear to me to be the plants which, in different climates, present specimens of the most extraordinary growth. An oak, discovered together with some Gallic helmets in 1809, in the turf pits of the department of the Somme, near the village of Yseux, seven leagues from Abbeville, was about the same size as the dragon-tree of Orotava. According to a memoir by M. Traullee, the trunk of this oak was 14 feet in diameter.) That in M. Franqui"s garden still bears every year both flowers and fruit. Its aspect forcibly exemplifies "that eternal youth of nature," which is an inexhaustible source of motion and of life.
The dracaena, which is seen only in cultivated spots in the Canary Islands, at Madeira, and Porto Santo, presents a curious phenomenon with respect to the migration of plants. It has never been found in a wild state on the continent of Africa. The East Indies is its real country. How has this tree been transplanted to Teneriffe, where it is by no means common? Does its existence prove, that, at some very distant period, the Guanches had connexions with other nations originally from Asia?* (* The form of the dragon-tree is exhibited in several species of the genus Dracaena, at the Cape of Good Hope, in China, and in New Zealand. But in New Zealand it is superseded by the form of the yucca; for the Dracaena borealis of Aiton is a Convallaria, of which it has all the appearance. The astringent juice, known in commerce by the name of dragon"s blood, is, according to the inquiries we made on the spot, the produce of several American plants, which do not belong to the same genus and of which some are lianas. At Laguna, toothpicks steeped in the juice of the dragon-tree are made in the nunneries, and are much extolled as highly useful for keeping the gums in a healthy state.)
On leaving Orotava, a narrow and stony pathway led us through a beautiful forest of chestnut trees (el monte de Castanos), to a site covered with brambles, some species of laurels, and arborescent heaths. The trunks of the latter grow to an extraordinary size; and the flowers with which they are loaded form an agreeable contrast, during a great part of the year, to the Hyperic.u.m canariense, which is very abundant at this height. We stopped to take in our provision of water under a solitary fir-tree. This station is known in the country by the name of Pino del Dornajito. Its height, according to the barometrical measurement of M. de Borda, is 522 toises; and it commands a magnificent prospect of the sea, and the whole of the northern part of the island. Near Pino del Dornajito, a little on the right of the pathway, is a copious spring of water, into which we plunged the thermometer, which fell to 15.4 degrees. At a hundred toises distance from this spring is another equally limpid. If we admit that these waters indicate nearly the mean heat of the place whence they issue, we may fix the absolute elevation of the station at 520 toises, supposing the mean temperature of the coast to be 21 degrees, and allowing one degree for the decrement of caloric corresponding under this zone to 93 toises. We should not be surprised if this spring remained a little below the heat of the air, since it probably takes its source in some more elevated part of the peak, and possibly communicates with the small subterranean glaciers of which we shall speak hereafter. The accordance just observed between the barometrical and thermometrical measures is so much more striking, because in mountainous countries, with steep declivities, the springs generally indicate too great a decrement of caloric, for they unite small currents of water, which filtrate at different heights, and their temperature is consequently the mean between the temperature of these currents. The spring of Dornajito has considerable reputation in the country; and at the time I was there, it was the only one known on the road which leads to the summit of the volcano. The formation of springs demands a certain regularity in the direction and inclination of the strata.
On a volcanic soil, porous and splintered rocks absorb the rain waters, and convey them to considerable depths. Hence arises that aridity observed in the greater part of the Canary Islands, notwithstanding the considerable height of their mountains, and the ma.s.s of clouds which navigators behold incessantly overhanging this archipelago.
From Pino del Dornajito to the crater of the volcano we continued to ascend without crossing a single valley; for the small ravines (barancos) do not merit this name. To the eye of the geologist the whole island of Teneriffe is but one mountain, the almost elliptical base of which is prolonged to the north-east, and in which may be distinguished several systems of volcanic rocks formed at different epochs. The Chahorra, or Montana Colorada, and the Urca, considered in the country as insulated volcanoes, are only little hills ab.u.t.ting on the peak, and masking its pyramidal form.
The great volcano, the lateral eruptions of which have given birth to vast promontories, is not however precisely in the centre of the island, and this peculiarity of structure appears the less surprising, if we recollect that, as the learned mineralogist M.
Cordier has observed, it is not perhaps the small crater of the Piton which has been the princ.i.p.al agent in the changes undergone by the island of Teneriffe.
Above the region of arborescent heaths, called Monte Verde, is the region of ferns. Nowhere, in the temperate zone, have I seen such an abundance of the pteris, blechnum, and asplenium; yet none of these plants have the stateliness of the arborescent ferns which, at the height of five or six hundred toises, form the princ.i.p.al ornament of equinoctial America. The root of the Pteris aquilina serves the inhabitants of Palma and Gomera for food; they grind it to powder, and mix with it a quant.i.ty of barley-meal. This composition, when boiled, is called gofio; the use of so homely an aliment is a proof of the extreme poverty of the lower order of people in the Canary Islands.
Monte Verde is intersected by several small and very arid ravines (canadas), and the region of ferns is succeeded by a wood of juniper trees and firs, which has suffered greatly from the violence of hurricanes. In this place, mentioned by some travellers under the name of Caravela,* (* "Philosophical Transactions" volume 29 page 317. Carabela is the name of a vessel with lateen sails.
The pines of the peak formerly were used as masts of vessels.) Mr.
Eden states that in the year 1705 he saw little flames, which, according to the doctrine of the naturalists of his time, he attributes to sulphurous exhalations igniting spontaneously. We continued to ascend, till we came to the rock of La Gayta and to Portillo: traversing this narrow pa.s.s between two basaltic hills, we entered the great plain of Spartium. At the time of the voyage of Laperouse, M. Manneron had taken the levels of the peak, from the port of Orotava to this elevated plain, near 1400 toises above the level of the sea; but the want of water, and the misconduct of the guides, prevented him from taking the levels to the top of the volcano. The results of the operation, (which was two-thirds completed,) unfortunately were not sent to Europe, and the work is still to be recommenced from the sea-coast.
We spent two hours and a half in crossing the Llano del Retama, which appears like an immense sea of sand. Notwithstanding the elevation of this site, the centigrade thermometer rose in the shade toward sunset, to 13.8 degrees, or 3.7 degrees higher than toward noon at Monte Verde. This augmentation of heat could be attributed only to the reverberation from the ground, and the extent of the plain. We suffered much from the suffocating dust of the pumice-stone, in which we were continually enveloped. In the midst of this plain are tufts of the retama, which is the Spartium nubigenum of Aiton. M. de Martiniere, one of the botanists who perished in the expedition of Laperouse, wished to introduce this beautiful shrub into Languedoc, where firewood is very scarce. It grows to the height of nine feet, and is loaded with odoriferous flowers, with which the goat hunters, that we met in our road, had decorated their hats. The goats of the peak, which are of a deep brown colour, are reckoned delicious food; they browse on the spartium, and have run wild in the deserts from time immemorial.
They have been transported to Madeira, where they are preferred to the goats of Europe.
As far as the rock of Gayta, or the entrance of the extensive Llano del Retama, the peak of Teneriffe is covered with beautiful vegetation. There are no traces of recent devastation. We might have imagined ourselves scaling the side of some volcano, the fire of which had been extinguished as remotely as that of Monte Cavo, near Rome; but scarcely had we reached the plain covered with pumice-stone, when the landscape changed its aspect, and at every step we met with large blocks of obsidian thrown out by the volcano. Everything here speaks perfect solitude. A few goats and rabbits only bound across the plain. The barren region of the peak is nine square leagues; and as the lower regions viewed from this point retrograde in the distance, the island appears an immense heap of torrefied matter, hemmed round by a scanty border of vegetation.
From the region of the Spartium nubigenum we pa.s.sed through narrow defiles, and small ravines hollowed at a very remote time by the torrents, first arriving at a more elevated plain (el Monton de Trigo), then at the place where we intended to pa.s.s the night. This station, which is more than 1530 toises above the coast, bears the name of the English Halt (Estancia de los Ingleses* (* This denomination was in use as early as the beginning of the last century. Mr. Eden, who corrupts all Spanish words, as do most travellers in our own times, calls it the Stancha: it is the Station des Rochers of M. Borda, as is proved by the barometrical heights there observed. These heights were in 1803, according to M.
Cordier, 19 inches 9.5 lines; and in 1776, according to Messrs.
Borda and Varela, 19 inches 9.8 lines; the barometer at Orotava keeping within nearly a line at the same height.)), no doubt because most of the travellers, who formerly visited the peak, were Englishmen. Two inclined rocks form a kind of cavern, which affords a shelter from the winds. This point, which is higher than the summit of the Canigou, can be reached on the backs of mules; and here has ended the expedition of numbers of travellers, who on leaving Orotava hoped to have ascended to the brink of the crater.
Though in the midst of summer, and under an African sky, we suffered from cold during the night. The thermometer descended as low as to five degrees. Our guides made a large fire with the dry branches of retama. Having neither tents nor cloaks, we lay down on some ma.s.ses of rock, and were singularly incommoded by the flame and smoke, which the wind drove towards us. We had attempted to form a kind of screen with cloths tied together, but our enclosure took fire, which we did not perceive till the greater part had been consumed by the flames. We had never pa.s.sed a night on a point so elevated, and we then little imagined that we should, one day, on the ridge of the Cordilleras, inhabit towns higher than the summit of the volcano we were to scale on the morrow. As the temperature diminished, the peak became covered with thick clouds. The approach of night interrupts the play of the ascending current, which, during the day, rises from the plains towards the high regions of the atmosphere; and the air, in cooling, loses its capacity of suspending water. A strong northerly wind chased the clouds; the moon at intervals, shooting through the vapours, exposed its disk on a firmament of the darkest blue; and the view of the volcano threw a majestic character over the nocturnal scenery. Sometimes the peak was entirely hidden from our eyes by the fog, at other times it broke upon us in terrific proximity; and, like an enormous pyramid, threw its shadow over the clouds rolling beneath our feet.
About three in the morning, by the sombrous light of a few fir torches, we started on our journey to the summit of the Piton. We scaled the volcano on the north-east side, where the declivities are extremely steep; and after two hours" toil, we reached a small plain, which, on account of its elevated position, bears the name of Alta Vista. This is the station of the neveros, those natives, whose occupation it is to collect ice and snow, which they sell in the neighbouring towns. Their mules, better practised in climbing mountains than those hired by travellers, reach Alta Vista, and the neveros are obliged to transport the snow to that place on their backs. Above this point commences the Malpays, a term by which is designated here, as well as in Mexico, Peru, and every other country subject to volcanoes, a ground dest.i.tute of vegetable mould, and covered with fragments of lava.
We turned to the right to examine the cavern of ice, which is at the elevation of 1728 toises, consequently below the limit of the perpetual snows in this zone. Probably the cold which prevails in this cavern, is owing to the same causes which perpetuate the ice in the crevices of Mount Jura and the Apennines, and on which the opinions of naturalists are still much divided. This natural ice-house of the peak has, nevertheless, none of those perpendicular openings, which give emission to the warm air, while the cold air remains undisturbed at the bottom. It would seem that the ice is preserved in it on account of its ma.s.s, and because its melting is r.e.t.a.r.ded by the cold, which is the consequence of quick evaporation. This small subterraneous glacier is situated in a region, the mean temperature of which is probably not under three degrees; and it is not, like the true glaciers of the Alps, fed by the snow waters that flow from the summits of the mountains. During winter the cavern is filled with ice and snow; and as the rays of the sun do not penetrate beyond the mouth, the heats of summer are not sufficient to empty the reservoir. The existence of a natural ice-house depends, consequently, rather on the quant.i.ty of snow which enters it in winter, and the small influence of the warm winds in summer, than on the absolute elevation of the cavity, and the mean temperature of the layer of air in which it is situated.
The air contained in the interior of a mountain is not easily displaced, as is exemplified by Monte Testaccio at Rome, the temperature of which is so different from that of the surrounding atmosphere. On Chimborazo enormous heaps of ice are found covered with sand, and, in the same manner as at the peak, far below the inferior limit of the perpetual snows.
It was near the Ice-Cavern (Cueva del Hielo), that, in the voyage of Laperouse, Messrs. Lamanon and Monges made their experiments on the temperature of boiling water. These naturalists found it 88.7 degrees, the barometer at nineteen inches one line. In the kingdom of New Grenada, at the chapel of Guadaloupe, near Santa-Fe de Bogota, I have seen water boil at 89.9 degrees, under a pressure of 19 inches 1.9 lines, At Tambores, in the province of Popayan, Senor Caldas found the heat of boiling water 89.5 degrees, the barometer being at 18 inches 11.6 lines. These results might lead us to suspect, that, in the experiment of M. Lamanon, the water had not reached the maximum of its temperature.
Day was beginning to dawn when we left the ice-cavern. We observed, during the twilight, a phenomenon which is not unusual on high mountains, but which the position of the volcano we were scaling rendered very striking. A layer of white and fleecy clouds concealed from us the sight of the ocean, and the lower region of the island. This layer did not appear above 800 toises high; the clouds were so uniformly spread, and kept so perfect a level, that they wore the appearance of a vast plain covered with snow. The colossal pyramid of the peak, the volcanic summits of Lancerota, of Forteventura, and the isle of Palma, were like rocks amidst this vast sea of vapours, and their black tints were in fine contrast with the whiteness of the clouds.
While we were climbing over the broken lavas of the Malpays, we perceived a very curious optical phenomenon, which lasted eight minutes. We thought we saw on the east side small rockets thrown into the air. Luminous points, about seven or eight degrees above the horizon, appeared first to move in a vertical direction; but their motion was gradually changed into a horizontal oscillation.
Our fellow-travellers, our guides even, were astonished at this phenomenon, without our having made any remark on it to them. We thought, at first sight, that these luminous points, which floated in the air, indicated some new eruption of the great volcano of Lancerota; for we recollected that Bouguer and La Condamine, in scaling the volcano of Pichincha, were witnesses of the eruption of Cotopaxi. But the illusion soon ceased, and we found that the luminous points were the images of several stars magnified by the vapours. These images remained motionless at intervals, they then seemed to rise perpendicularly, descended sideways, and returned to the point whence they had departed. This motion lasted one or two seconds. Though we had no exact means of measuring the extent of the lateral shifting, we did not the less distinctly observe the path of the luminous point. It did not appear double from an effect of mirage, and left no trace of light behind. Bringing, with the telescope of a small s.e.xtant by Troughton, the stars into contact with the lofty summit of a mountain in Lancerota, I observed that the oscillation was constantly directed towards the same point, that is to say, towards that part of the horizon where the disk of the sun was to appear; and that, making allowance for the motion of the star in its declination, the image returned always to the same place. These appearances of lateral refraction ceased long before daylight rendered the stars quite invisible. I have faithfully related what we saw during the twilight, without undertaking to explain this extraordinary phenomenon, of which I published an account in Baron Zach"s Astronomical Journal, twelve years ago. The motion of the vesicular vapours, caused by the rising of the sun; the mingling of several layers of air, the temperature and density of which were very different, no doubt contributed to produce an apparent movement of the stars in the horizontal direction. We see something similar in the strong undulations of the solar disk, when it cuts the horizon; but these undulations seldom exceed twenty seconds, while the lateral motion of the stars, observed at the peak, at more than 1800 toises, was easily distinguished by the naked eye, and seemed to exceed all that we have thought it possible to consider hitherto as the effect of the refraction of the light of the stars. On the top of the Andes, at Antisana, I observed the sun-rise, and pa.s.sed the whole night at the height of 2100 toises, without noting any appearance resembling this phenomenon.
I was anxious to make an exact observation of the instant of sun-rising at an elevation so considerable as that we had reached on the peak of Teneriffe. No traveller, furnished with instruments, had as yet taken such an observation. I had a telescope and a chronometer, which I knew to be exceedingly correct. In the part where the sun was to appear the horizon was free from vapour. We perceived the upper limb at 4 hours 48 minutes 55 seconds apparent time, and what is very remarkable, the first luminous point of the disk appeared immediately in contact with the limit of the horizon, consequently we saw the true horizon; that is to say, a part of the sea farther distant than 43 leagues. It is proved by calculation that, under the same parallel in the plain, the rising would have begun at 5 hours 1 minute 50.4 seconds, or 11 minutes 51.3 seconds later than at the height of the peak. The difference observed was 12 minutes 55 seconds, which arose no doubt from the uncertainty of the refraction for a zenith distance, of which observations are wanting.
We were surprised at the extreme slowness with which the lower limb of the sun seemed to detach itself from the horizon. This limb was not visible till 4 hours 56 minutes 56 seconds. The disc of the sun, much flattened, was well defined; during the ascent there was neither double image nor lengthening of the lower limb. The duration of the sun"s rising being triple that which we might have expected in this lat.i.tude, we must suppose that a fog-bank, very uniformly extended, concealed the true horizon, and followed the sun in its ascent. Notwithstanding the libration of the stars,*
which we had observed towards the east, we could not attribute the slowness of the rising to an extraordinary refraction of the rays occasioned by the horizon of the sea; for it is precisely at the rising of the sun, as Le Gentil daily observed at Pondicherry, and as I have several times remarked at c.u.mana, that the horizon sinks, on account of the elevation of temperature in the stratum of the air which lies immediately over the surface of the ocean. (* A celebrated astronomer, Baron Zach, has compared this phenomenon of an apparent libration of the stars to that described in the Georgics (lib. 50 v. 365). But this pa.s.sage relates only to the falling stars, which the ancients, (like the mariners of modern times) considered as a prognostic of wind.)
The road, which we were obliged to clear for ourselves across the Malpays, was extremely fatiguing. The ascent is steep, and the blocks of lava rolled from beneath our feet. I can compare this part of the road only to the Moraine of the Alps or that ma.s.s of pebbly stones which we find at the lower extremity of the glaciers.
At the peak the lava, broken into sharp pieces, leaves hollows, in which we risked falling up to our waists. Unfortunately the listlessness of our guides contributed to increase the difficulty of this ascent. Unlike the guides of the valley of Chamouni, or the nimble-footed Guanches, who could, it is a.s.serted, seize the rabbit or wild goat in its course, our Canarian guides were models of the phlegmatic. They had wished to persuade us on the preceding evening not to go beyond the station of the rocks. Every ten minutes they sat down to rest themselves, and when un.o.bserved they threw away the specimens of obsidian and pumice-stone, which we had carefully collected. We discovered at length that none of them had ever visited the summit of the volcano.
After three hours" walking, we reached, at the extremity of the Malpays, a small plain, called La Rambleta, from the centre of which the Piton, or Sugar-loaf, takes its rise. On the side toward Orotava the mountain resembles those pyramids with steps that are seen at Fayoum and in Mexico; for the elevated plains of Retama and Rambleta form two tiers, the first of which is four times higher than the second. If we suppose the total height of the Peak to be 1904 toises, the Rambleta is 1820 toises above the level of the sea. Here are found those spiracles, which are called by the natives the Nostrils of the Peak (Narices del Pico). Watery and heated vapours issue at intervals from several crevices in the ground, and the thermometer rose to 43.2 degrees. M. Labillardiere had found the temperature of these vapours, eight years before us, 53.7 degrees; a difference which does not perhaps prove so much a diminution of activity in the volcano, as a local change in the heating of its internal surface. The vapours have no smell, and seem to be pure water. A short time before the great eruption of Mount Vesuvius, in 1805, M. Gay-Lussac and myself had observed that water, under the form of vapour, in the interior of the crater, did not redden paper which had been dipped in syrup of violets. I cannot, however, admit the bold hypothesis, according to which the Nostrils of the Peak are to be considered as the vents of an immense apparatus of distillation, the lower part of which is situated below the level of the sea. Since the time when volcanoes have been carefully studied, and the love of the marvellous has been less apparent in works on geology, well founded doubts have been raised respecting these direct and constant communications between the waters of the sea and the focus of the volcanic fire.*
(* This question has been examined with much sagacity by M.
Brieslak, in his "Introduzzione alla Geologia," tome 2 pages 302, 323, 347. Cotopaxi and Popocatepetl, which I saw ejecting smoke and ashes, in 1804, are farther from both the Pacific and the Gulf of the Antilles, than Gren.o.ble is from the Mediterranean, and Orleans from the Atlantic. We must not consider the fact as merely accidental, that we have not yet discovered an active volcano more than 40 leagues distant from the ocean; but I consider the hypothesis, that the waters of the sea are absorbed, distilled, and decomposed by volcanoes, as very doubtful.) We may find a very simple explanation of a phenomenon, that has in it nothing very surprising. The peak is covered with snow during part of the year; we ourselves found it still so in the plain of Rambleta. Messrs.
O"Donnel and Armstrong discovered in 1806 a very abundant spring in the Malpays, a hundred toises above the cavern of ice, which is perhaps fed partly by this snow. Everything consequently leads us to presume that the peak of Teneriffe, like the volcanoes of the Andes, and those of the island of Manilla, contains within itself great cavities, which are filled with atmospherical water, owing merely to filtration. The aqueous vapours exhaled by the Narices and crevices of the crater, are only those same waters heated by the interior surfaces down which they flow.