STAY AT TENERIFE.
JOURNEY FROM SANTA CRUZ TO OROTAVA.
EXCURSION TO THE SUMMIT OF THE PEAK OF TEYDE.
From the time of our departure from Graciosa, the horizon continued
so hazy, that, notwithstanding the considerable height of the
mountains of Canary,* (* Isla de la Gran Canaria.) we did not
discover that island till the evening of the 18th of June. It is
the granary of the archipelago of the Fortunate Islands; and, what
is very remarkable in a region situated beyond the limits of the
tropics, we were assured, that in some districts, there are two
wheat harvests in the year; one in February, and the other in June.
Canary has never been visited by a learned mineralogist; yet this
island is so much the more worthy of observation, as the
physiognomy of its mountains, disposed in parallel chains, appeared
to me to differ entirely from that of the summits of Lancerota and
Teneriffe. Nothing is more interesting to the geologist, than to
observe the relations, on the same point of the globe, between
volcanic countries, and those which are primitive or secondary.
When the Canary Islands shall have been examined, in all the parts
which compose the system of these mountains, we shall find that we
have been too precipitate in considering the whole group as raised
by the action of submarine fires.
On the morning of the 19th, we discovered the point of Naga, but
the peak of Teneriffe was still invisible: the land, obscured by a
thick mist, presented forms that were vague and confused. As we
approached the road of Santa Cruz we observed that the mist, driven
by the winds, drew nearer to us. The sea was strongly agitated, as
it most commonly is in those latitudes. We anchored after several
soundings, for the mist was so thick, that we could scarcely
distinguish objects at a few cables' distance; but at the moment we
began to salute the place, the fog was instantly dispelled. The
peak of Teyde appeared in a break above the clouds, and the first
rays of the sun, which had not yet risen on us, illumined the
summit of the volcano.
We hastened to the prow of the vessel to behold the magnificent
spectacle, and at the same instant we saw four English vessels
lying to, and very near our stern. We had passed without being
perceived, and the same mist which had concealed the peak from our
view, had saved us from the risk of being carried back to Europe.
The Pizarro stood in as close as possible to the fort, to be under
its protection. It was on this shore, that, in the landing
attempted by the English two years before our arrival, in July
1797, admiral Nelson had his arm carried off by a cannon-ball.
The situation of the town of Santa Cruz is very similar to that of
La Guayra, the most frequented port of the province of Caraccas.
The heat is excessive in both places, and from the same causes; but
the aspect of Santa Cruz is more gloomy. On a narrow and sandy
beach, houses of dazzling whiteness, with flat roofs, and windows
without glass, are built close against a wall of black
perpendicular rock, devoid of vegetation. A fine mole, built of
freestone, and the public walk planted with poplars, are the only
objects which break the sameness of the landscape. The view of the
peak, as it presents itself above Santa Cruz, is much less
picturesque than that we enjoy from the port of Orotava. There, a
highly cultured and smiling plain presents a pleasing contrast to
the wild aspect of the volcano. From the groups of palm trees and
bananas which line the coast, to the region of the arbutus, the
laurel, and the pine, the volcanic rock is crowned with luxuriant
vegetation. We easily conceive how the inhabitants, even of the
beautiful climates of Greece and Italy, might fancy they recognised
one of the Fortunate Isles in the western part of Teneriffe. The
eastern side, that of Santa Cruz, on the contrary, is every where
stamped with sterility. The summit of the peak is not more arid
than the promontory of basaltic lava, which stretches towards the
point of Naga, and on which succulent plants, springing up in the
clefts of the rocks, scarcely indicate a preparation of soil. At
the port of Orotava, the top of the Piton subtends an angle in
height of more than eleven degrees and a half; while at the mole of
Santa Cruz* (* The oblique distances from the top of the volcano to
Orotava and to Santa Cruz are nearly 8600 toises and 22,500 toises.)
the angle scarcely exceeds 4 degrees 36 minutes.
Notwithstanding this difference, and though in the latter place the
volcano rises above the horizon scarcely as much as Vesuvius seen
from the mole of Naples, the aspect of the peak is still very
majestic, when those who anchor in the road discern it for the
first time. The Piton alone was visible to us; its cone projected
itself on a sky of the purest blue, whilst dark thick clouds
enveloped the rest of the mountain to the height of 1800 toises.
The pumice-stone, illumined by the first rays of the sun, reflected
a reddish light, like that which tinges the summits of the higher
Alps. This light by degrees becomes dazzlingly white; and, deceived
like most travellers, we thought that the peak was still covered
with snow, and that we should with difficulty reach the edge of the
crater.
We have remarked, in the Cordillera of the Andes, that the conical
mountains, such as Cotopaxi and Tungurahua, are oftener seen free
from clouds, than those of which the tops are broken into bristly
points, like Antisana and Pichincha; but the peak of Teneriffe,
notwithstanding its pyramidical form, is a great part of the year
enveloped in vapours, and is sometimes, during several weeks,
invisible from the road of Santa Cruz. Its position to the west of
an immense continent, and its insulated situation in the midst of
the sea, are no doubt the causes of this phenomenon. Navigators are
well aware that even the smallest islets, and those which are
without mountains, collect and harbour the clouds. The decrement of
heat is also different above the plains of Africa, and above the
surface of the Atlantic; and the strata of air, brought by the
trade winds, cool in proportion as they advance towards the west.
If the air has been extremely dry above the burning sands of the
desert, it is very quickly saturated when it enters into contact
with the surface of the sea, or with the air that lies on that
surface. It is easy to conceive, therefore, why vapours become
visible in the atmospherical strata, which, at a distance from the
continent, have no longer the same temperature as when they began
to be saturated with water. The considerable mass of a mountain,
rising in the midst of the Atlantic, is also an obstacle to the
clouds, which are driven out to sea by the winds.
On entering the streets of Santa Cruz, we felt a suffocating heat,
though the thermometer was not above twenty-five degrees. Those who
have for a long time inhaled the air of the sea suffer every time
they land; not because this air contains more oxygen than the air
on shore, as has been erroneously supposed, but because it is less
charged with those gaseous combinations, which the animal and
vegetable substances, and the mud resulting from their
decomposition, pour into the atmosphere. Miasms that escape
chemical analysis have a powerful effect on our organs, especially
when they have not for a long while been exposed to the same kind
of irritation.
Santa Cruz, the Anaza of the Guanches, is a neat town, with a
population of 8000 souls. I was not struck with the vast number of
monks and secular ecclesiastics, which travellers have thought
themselves bound to find in every country under the Spanish
government; nor shall I stop to enter into the description of the
churches; the library of the Dominicans, which contains scarcely a
few hundred volumes; the mole, where the inhabitants assemble to
inhale the freshness of the evening breeze; or the famed monument
of Carrara marble, thirty feet high, dedicated to Our Lady of
Candelaria, in memory of the miraculous appearance of the Virgin,
in 1392, at Chimisay, near Guimar. The port of Santa Cruz may be
considered as a great caravanserai, on the road to America and the
Indies. Every traveller who writes the narrative of his adventures,
begins by a description of Madeira and Teneriffe; and if in the
natural history of these islands there yet remains an immense field
untrodden, we must admit that the topography of the little towns of
Funchal, Santa Cruz, Laguna, and Orotava, leaves scarcely anything
untold.
The recommendation of the court of Madrid procured for us, in the
Canaries, as in all the other Spanish possessions, the most
satisfactory reception. The captain-general gave us immediate
permission to examine the island. Colonel Armiaga, who commanded a
regiment of infantry, received us into his house with kind
hospitality. We could not cease admiring the banana, the papaw
tree, the Poinciana pulcherrima, and other plants, which we had
hitherto seen only in hot-houses, cultivated in his garden in the
open air. The climate of the Canaries however is not warm enough to
ripen the real Platano Arton, with triangular fruit from seven to
eight inches long, and which, requiring a temperature of 24
centesimal degrees, does not flourish even in the valley of
Caracas. The bananas of Teneriffe are those named by the Spanish
planters Camburis or Guineos, and Dominicos. The Camburi, which
suffers least from cold, is cultivated with success even at Malaga,
where the temperature is only 18 degrees; but the fruit we see
occasionally at Cadiz comes from the Canary Islands by vessels
which make the passage in three or four days. In general, the musa,
known by every people under the torrid zone, though hitherto never
found in a wild state, has as great a variety of fruit as our apple
and pear trees. These varieties, which are confounded by the
greater part of botanists, though they require very different
climates, have become permanent by long cultivation.
We went to herborize in the evening in the direction of the fort of
Passo Alto, along the basaltic rocks that close the promontory of
Naga. We were very little satisfied with our harvest, for the
drought and dust had almost destroyed vegetation. The Cacalia
Kleinia, the Euphorbia canariensis, and several other succulent
plants, which draw their nourishment from the air rather than the
soil on which they grow, reminded us by their appearance, that this
group of islands belongs to Africa, and even to the most arid part
of that continent.
Though the captain of the Pizarro had orders to stop long enough at
Teneriffe to give us time to scale the summit of the peak, if the
snows did not prevent our ascent, we received notice, on account of
the blockade of the English ships, not to expect a longer delay
than four or five days. We consequently hastened our departure for
the port of Orotava, which is situated on the western declivity of
the volcano, where we were sure of finding guides. I could find no
one at Santa Cruz who had mounted the peak, and I was not surprised
at this. The most curious objects become less interesting, in
proportion as they are near to us; and I have known inhabitants of
Schaffhausen, in Switzerland, who had never seen the fall of the
Rhine but at a distance.
On the 20th of June, before sunrise, we began our excursion by
ascending to the Villa de Laguna, estimated to be at the elevation
of 350 toises above the port of Santa Cruz. We could not verify
this estimate of the height, the surf not having permitted us to
return on board during the night, to take our barometers and
dipping-needle. As we foresaw that our expedition to the peak would
be very precipitate, we consoled ourselves with the reflection that
it was well not to expose instruments which were to serve us in
countries less known by Europeans. The road by which we ascended to
Laguna is on the right of a torrent, or baranco, which in the rainy
season forms fine cascades; it is narrow and tortuous. Near the
town we met some white camels, which seemed to be very slightly
laden. The chief employment of these animals is to transport
merchandise from the custom-house to the warehouses of the
merchants. They are generally laden with two chests of Havannah
sugar, which together weigh 900 pounds; but this load may be
augmented to thirteen hundred-weight, or 52 arrobas of Castile.
Camels are not numerous at Teneriffe, whilst they exist by
thousands in the two islands of Lancerota and Forteventura; the
climate and vegetation of these islands, which are situated nearer
Africa, are more analogous to those of that continent. It is very
extraordinary, that this useful animal, which breeds in South
America, should be seldom propagated at Teneriffe. In the fertile
district of Adexe only, where the plantations of the sugar-cane are
most considerable, camels have sometimes been known to breed. These
beasts of burden, as well as horses, were brought into the Canary
Islands in the fifteenth century by the Norman conquerors. The
Guanches were previously unacquainted with them; and this fact
seems to be very well accounted for by the difficulty of
transporting an animal of such bulk in frail canoes, without the
necessity of considering the Guanches as a remnant of the people of
Atlantis, or a different race from that of the western Africans.
The hill, on which the town of San Christobal de la Laguna is
built, belongs to the system of basaltic mountains, which,
independent of the system of less ancient volcanic rocks, form a
broad girdle around the peak of Teneriffe. The basalt on which we
walked was darkish brown, compact, half-decomposed, and when
breathed on, emitted a clayey smell. We discovered amphibole,
olivine,* (* Peridot granuliforme. Hauy.) and translucid pyroxenes,
* (* Augite.--Werner.) with a perfectly lamellar fracture, of a
pale olive green, and often crystallized in prisms of six planes.
The first of these substances is extremely rare at Teneriffe; and I
never found it in the lavas of Vesuvius; but those of Etna contain
it in abundance. Notwithstanding the great number of blocks, which
we stopped to break, to the great regret of our guides, we could
discover neither nepheline, leucite,* (* Amphigene.--Hauy.) nor
feldspar. This last, which is so common in the basaltic lavas of
the island of Ischia, does not begin to appear at Teneriffe, till
we approach the volcano. The rock of Laguna is not columnar, but is
divided into ledges, of small thickness, and inclined to the east
at an angle of 30 or 40 degrees. It has nowhere the appearance of a
current of lava flowing from the sides of the peak. If the present
volcano has given birth to these basalts, we must suppose, that,
like the substances which compose the Somma, at the back of
Vesuvius, they are the effect of a submarine effusion, in which the
liquid mass has formed strata. A few arborescent Euphorbias, the
Cacalia Kleinia, and Indian figs (Cactus), which have become wild
in the Canary Islands, as well as in the south of Europe and the
whole continent of Africa, are the only plants we see on these arid
rocks. The feet of our mules were slipping every moment on beds of
stone, which were very steep. We nevertheless recognized the
remains of an ancient pavement. In these colonies we discover at
every step some traces of that activity which characterized the
Spanish nation in the 16th century.
As we approached Laguna, we felt the temperature of the atmosphere
gradually become lower. This sensation was so much the more
agreeable, as we found the air of Santa Cruz very oppressive. As
our organs are more affected by disagreeable impressions, the
change of temperature becomes still more sensible when we return
from Laguna to the port: we seem then to be drawing near the mouth
of a furnace. The same impression is felt, when, on the coast of
Caracas, we descend from the mountain of Avila to the port of La
Guayra. According to the law of the decrement of heat, three
hundred and fifty toises in height produce in this latitude only
three or four degrees difference in temperature. The heat which
overpowers the traveller on his entrance into Santa Cruz, or La
Guayra, must consequently be attributed to the reverberation from
the rocks, against which these towns are built.
The perpetual coolness which prevails at Laguna causes it to be
considered in the Canaries a delightful abode. Situated in a small
plain, surrounded by gardens, protected by a hill which is crowned
by a wood of laurels, myrtle, and arbutus, the capital of Teneriffe
is very beautifully placed. We should be mistaken if, relying on
the account of some travellers, we believed it seated on the border
of a lake. The rain sometimes forms a sheet of water of
considerable extent; and the geologist, who beholds in everything
the past rather than the present state of nature, can have no doubt
but that the whole plain is a great basin dried up. Laguna has
fallen from its opulence, since the lateral eruptions of the
volcano have destroyed the port of Garachico, and since Santa Cruz
has become the central point of the commerce of the island. It
contains only 9000 inhabitants, of whom nearly 400 are monks,
distributed in six convents. The town is surrounded with a great
number of windmills, which indicate the cultivation of wheat in
these high countries. I shall observe on this occasion, that
different kinds of grain were known to the Guanches. They called
wheat at Teneriffe tano, at Lancerota triffa; barley, in the grand
Canary, bore the name of aramotanoque, and at Lancerota it was
called tamosen. The flour of roasted barley (gofio) and goat's-milk
constituted the principal food of the people, on the origin of
which so many systematic fables have been current. These aliments
sufficiently prove that the race of the Guanches belonged to the
nations of the old continent, perhaps to those of Caucasus, and not
like the rest of the Atlantides,* to the inhabitants of the New
World (* Without entering here into any discussion respecting the
existence of the Atlantis, I may cite the opinion of Diodorus
Siculus, according to whom the Atlantides were ignorant of the use
of corn, because they were separated from the rest of mankind
before these gramina were cultivated.); these, before the arrival
of the Europeans, were unacquainted with corn, milk, and cheese.
A great number of chapels, which the Spaniards call ermitas,
encircle the town of Laguna. Shaded by trees of perpetual verdure,
and erected on small eminences, these chapels add to the
picturesque effect of the landscape. The interior of the town is
not equal to its external appearance. The houses are solidly built,
but very antique, and the streets seem deserted. A botanist ought
not to complain of the antiquity of the edifices. The roofs and
walls are covered with Canary house-leek and those elegant
trichomanes, mentioned by every traveller. These plants are
nourished by the abundant mists.
Mr. Anderson, the naturalist in the third voyage of captain Cook,
advises physicians to send their patients to Teneriffe, on account
of the mildness of the temperature and the equal climate of the
Canaries. The ground on these islands rises in an amphitheatre, and
presents simultaneously, as in Peru and Mexico, the temperature of
every climate, from the heat of Africa to the cold of the higher
Alps. Santa Cruz, the port of Orotava, the town of the same name,
and that of Laguna, are four places, the mean temperatures of which
form a descending series. In the south of Europe the change of the
seasons is too sensibly felt to present the same advantages.
Teneriffe, on the contrary, situated as it were on the threshold of
the tropics, though but a few days' sail from Spain, shares in the
charms which nature has lavished on the equinoctial regions.
Vegetation here displays some of her fairest and most majestic
forms in the banana and the palm-tree. He who is alive to the
charms of nature finds in this delicious island remedies still more
potent than the climate. No abode appeared to me more fitted to
dissipate melancholy, and restore peace to the perturbed mind, than
that of Teneriffe or Madeira. These advantages are the effect not
of the beauty of the site and the purity of the air alone: the
moral feeling is no longer harrowed up by the sight of slavery, the
presence of which is so revolting in the West Indies, and in every
other place to which European colonists have conveyed what they
call their civilization and their industry.
In winter the climate of Laguna is extremely foggy, and the
inhabitants often complain of the cold. A fall of snow, however,
has never been seen; a fact which may seem to indicate that the
mean temperature of this town must be above 18.7 degrees (15
degrees R.), that is to say, higher than that of Naples. I do not
lay this down as an unexceptional conclusion, for in winter the
refrigeration of the clouds does not depend so much on the mean
temperature of the whole year, as on the instantaneous diminution
of heat to which a district is exposed by its local situation. The
mean temperature of the capital of Mexico, for instance, is only
16.8 degrees (13.5 degrees R.), nevertheless, in the space of a
hundred years snow has fallen only once, while in the south of
Europe and in Africa it snows in places where the mean temperature
is above 19 degrees.
The vicinity of the sea renders the climate of Laguna more mild in
winter than might be expected, arising from its elevation above the
level of the ocean. I was astonished to learn that M. Broussonnet
had planted in the midst of this town, in the garden of the Marquis
de Nava, the bread-fruit tree (Artocarpus incisa), and
cinnamon-tree (Laurus Cinnamomum). These valuable productions of
the South Sea and the East Indies are naturalized there as well as
at Orotava. Does not this fact prove that the bread-fruit might
flourish in Calabria, Sicily, and Granada? The culture of the
coffee-tree has not equally succeeded at Laguna, though its fruit
ripens at Teguesta, as well as between the port of Orotava and the
village of St. Juan de la Rambla. It is probable that some local
circumstances, perhaps the nature of the soil and the winds that
prevail in the flowering season, are the cause of this phenomenon.
In other regions, in the neighbourhood of Naples, for instance, the
coffee-tree thrives abundantly, though the mean temperature
scarcely rises above 18 centigrade degrees.
No person has ascertained in the island of Teneriffe, the lowest
height at which snow falls every year. This fact, though easy of
verification by barometrical measurements, has hitherto been
generally neglected under every zone. It is nevertheless highly
interesting both to agriculture in the colonies and meteorology,
and fully as important as the measure of the limit of the perpetual
snows. My observations furnished me with the data, set down in the
following table:--
Column 1: North latitude.
Column 2: Lowest height in toises at which snow falls.
Column 3: Lowest height in metres at which snow falls.
Column 4: Inferior limit in toises of the perpetual snows.
Column 5: Inferior limit in metres of the perpetual snows.
Column 6: Difference in toises of columns 4 and 5.
Column 7: Difference in metres of columns 4 and 5.
Column 8: Mean temperature degrees centigrade.
Column 9: Mean temperature degrees Reaum.
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 circumstances, exist. Thus it sometimes
snows, though seldom, at Naples, at Lisbon, and even at Malaga,
consequently as low as the 37th degree of latitude: 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 latitude 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 pass 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 asserted
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 masses 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 quantity 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 nobles; and those feudal institutions, 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
mass; 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 passed 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 passage, 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 Cumana, 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 passionately 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 passed 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 assured 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 analogies, 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 principal 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 passed 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
assured, that these last were as little productive here as on the
coast of Cumana. 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 documents 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 circumference 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 circumference 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 (Platanus 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
Hypericum 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
mass 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 abutting 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 principal 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 principal
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 quantity 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 pass 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 passed 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 pass 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 masses 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 passed 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 destitute 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 mass, and because its
melting is retarded 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 quantity 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 sextant 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 passed 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 latitude, 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 Cumana, 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 passage 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 mass 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 asserted, 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 unobserved 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 Grenoble 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.
We had yet to scale the steepest part of the mountain, the Piton,
which forms the summit. The slope of this small cone, covered with
volcanic ashes, and fragments of pumice-stone, is so steep, that it
would have been almost impossible to reach the top, had we not
ascended by an old current of lava, the debris of which have
resisted the ravages of time. These debris form a wall of scorious
rock, which stretches into the midst of the loose ashes. We
ascended the Piton by grasping these half-decomposed scoriae, which
often broke in our hands. We employed nearly half an hour to scale
a hill, the perpendicular height of which is scarcely ninety
toises. Vesuvius, three times lower than the peak of Teneriffe, is
terminated by a cone of ashes almost three times higher, but with a
more accessible and easy slope. Of all the volcanoes which I have
visited, that of Jorullo, in Mexico, is the only one that is more
difficult to climb than the Peak, because the whole mountain is
covered with loose ashes.
When the Sugar-loaf (el Piton) is covered with snow, as it is in
the beginning of winter, the steepness of its declivity may be very
dangerous to the traveller. M. Le Gros showed us the place where
captain Baudin was nearly killed when he visited the Peak of
Teneriffe. That officer had the courage to undertake, in company
with the naturalists Advenier, Mauger, and Riedle, an excursion to
the top of the volcano about the end of December, 1797. Having
reached half the height of the cone, he fell, and rolled down as
far as the small plain of Rambleta; happily a heap of lava, covered
with snow, hindered him from rolling farther with accelerated
velocity. I have been told, that in Switzerland a traveller was
suffocated by rolling down the declivity of the Col de Balme, over
the compact turf of the Alps.
When we gained the summit of the Piton, we were surprised to find
scarcely room enough to seat ourselves conveniently. We were
stopped by a small circular wall of porphyritic lava, with a base
of pitchstone, which concealed from us the view of the crater.* (*
Called La Caldera, or the caldron of the peak, a denomination which
recalls to mind the Oules of the Pyrenees.) The west wind blew with
such violence that we could scarcely stand. It was eight in the
morning, and we suffered severely from the cold, though the
thermometer kept a little above freezing point. For a long time we
had been accustomed to a very high temperature, and the dry wind
increased the feeling of cold, because it carried off every moment
the small atmosphere of warm and humid air, which was formed around
us from the effect of cutaneous perspiration.
The brink of the crater of the peak bears no resemblance to those
of most of the other volcanoes which I have visited: for instance,
the craters of Vesuvius, Jorullo, and Pichincha. In these the Piton
preserves its conic figure to the very summit: the whole of their
declivity is inclined the same number of degrees, and uniformly
covered with a layer of pumice-stone very minutely divided; when we
reach the top of these volcanoes, nothing obstructs the view of the
bottom of the crater. The peaks of Teneriffe and Cotopaxi, on the
contrary, are of very different construction. At their summit a
circular wall surrounds the crater; which wall, at a distance, has
the appearance of a small cylinder placed on a truncated cone. On
Cotopaxi this peculiar construction is visible to the naked eye at
more than 2000 toises distance; and no person has ever reached the
crater of that volcano. On the peak of Teneriffe, the wall, which
surrounds the crater like a parapet, is so high, that it would be
impossible to reach the Caldera, if, on the eastern side, there was
not a breach, which seems to have been the effect of a flowing of
very old lava. We descended through this breach toward the bottom
of the funnel, the figure of which is elliptic. Its greater axis
has a direction from north-west to south-east, nearly north 35
degrees west. The greatest breadth of the mouth appeared to us to
be 300 feet, the smallest 200 feet, which numbers agree very nearly
with the measurement of MM. Verguin, Varela, and Borda.
It is easy to conceive, that the size of a crater does not depend
solely on the height and mass of the mountain, of which it forms
the principal air-vent. This opening is indeed seldom in direct
ratio with the intensity of the volcanic fire, or with the activity
of the volcano. At Vesuvius, which is but a hill compared with the
Peak of Teneriffe, the diameter of the crater is five times
greater. When we reflect, that very lofty volcanoes throw out less
matter from their summits than from lateral openings, we should be
led to think, that the lower the volcanoes, their force and
activity being the same, the more considerable ought to be their
craters. In fact, there are immense volcanoes in the Andes, which
have but very small openings; and we might establish as a
geological principle, that the most colossal mountains have craters
of little extent at the summits, if the Cordilleras did not present
many instances to the contrary.* (* The great volcanoes of Cotopaxi
and Rucupichincha have craters, the diameters of which, according
to my measurements, exceed 400 and 700 toises.) I shall have
occasion, in the progress of this work, to cite a number of facts,
which will throw some light on what may be called the external
structure of volcanoes. This structure is as varied as the volcanic
phenomena themselves; and in order to raise ourselves to geological
conceptions worthy of the greatness of nature, we must set aside
the idea that all volcanoes are formed after the model of Vesuvius,
Stromboli, and Etna.
The external edges of the Caldera are almost perpendicular. Their
appearance is somewhat like the Somma, seen from the Atrio dei
Cavalli. We descended to the bottom of the crater on a train of
broken lava, from the eastern breach of the enclosure. The heat was
perceptible only in a few crevices, which gave vent to aqueous
vapours with a peculiar buzzing noise. Some of these funnels or
crevices are on the outside of the enclosure, on the external brink
of the parapet that surrounds the crater. We plunged the
thermometer into them, and saw it rise rapidly to 68 and 75
degrees. It no doubt indicated a higher temperature, but we could
not observe the instrument till we had drawn it up, lest we should
burn our hands. M. Cordier found several crevices, the heat of
which was that of boiling water. It might be thought that these
vapours, which are emitted in gusts, contain muriatic or sulphurous
acid; but when condensed, they have no particular taste; and
experiments, which have been made with re-agents, prove that the
chimneys of the peak exhale only pure water. This phenomenon,
analogous to that which I observed in the crater of Jorullo,
deserves the more attention, as muriatic acid abounds in the
greater part of volcanoes, and as M. Vauquelin has discovered it
even in the porphyritic lavas of Sarcouy in Auvergne.
I sketched on the spot a view of the interior edge of the crater,
as it presented itself in the descent by the eastern break. Nothing
is more striking than the manner in which these strata of lava are
piled on one another, exhibiting the sinuosities of the calcareous
rock of the higher Alps. These enormous ledges, sometimes
horizontal, sometimes inclined and undulating, are indicative of
the ancient fluidity of the whole mass, and of the combination of
several deranging causes, which have determined the direction of
each flow. The top of the circular wall exhibits those curious
ramifications which we find in coke. The northern edge is most
elevated. Towards the south-west the enclosure is considerably sunk
and an enormous mass of scorious lava seems glued to the extremity
of the brink. On the west the rock is perforated; and a large
opening gives a view of the horizon of the sea. The force of the
elastic vapours perhaps formed this natural aperture, at the time
of some inundation of lava thrown out from the crater.
The inside of this funnel indicates a volcano, which for thousands
of years has vomited no fire but from its sides. This conclusion is
not founded on the absence of great openings, which might be
expected in the bottom of the Caldera. Those whose experience is
founded on personal observation, know that several volcanoes, in
the intervals of an eruption, appear filled up, and almost
extinguished; but that in these same mountains, the crater of the
volcano exhibits layers of scoriae, rough, sonorous, and shining.
We observe hillocks and intumescences caused by the action of the
elastic vapours, cones of broken scoriae and ashes which cover the
funnels. None of these phenomena characterise the crater of the
peak of Teneriffe; its bottom is not in the state which ensues at
the close of an eruption. From the lapse of time, and the action of
the vapours, the inside walls are detached, and have covered the
basin with great blocks of lithoid lavas.
The bottom of the Caldera is reached without danger. In a volcano,
the activity of which is principally directed towards the summit,
such as Vesuvius, the depth of the crater varies before and after
each eruption; but at the peak of Teneriffe the depth appears to
have remained unchanged for a long time. Eden, in 1715, estimated
it at 115 feet; Cordier, in 1803, at 110 feet. Judging by mere
inspection, I should have thought the funnel of still less depth.
Its present state is that of a solfatara; and it is rather an
object of curious investigation, than of imposing aspect. The
majesty of the site consists in its elevation above the level of
the sea, in the profound solitude of these lofty regions, and in
the immense space over which the eye ranges from the summit of the
mountain.
The wall of compact lava, forming the enclosure of the Caldera, is
snow-white at its surface. The same colour prevails in the inside
of the Solfatara of Puzzuoli. When we break these lavas, which
might be taken at some distance for calcareous stone, we find in
them a blackish brown nucleus. Porphyry, with basis of pitch-stone,
is whitened externally by the slow action of the vapours of
sulphurous acid gas. These vapours rise in abundance; and what is
rather remarkable, through crevices which seem to have no
communication with the apertures that emit aqueous vapours. We may
be convinced of the presence of the sulphurous acid, by examining
the fine crystals of sulphur, which are everywhere found in the
crevices of the lava. This acid, combined with the water with which
the soil is impregnated, is transformed into sulphuric acid by
contact with the oxygen of the atmosphere. In general, the humidity
in the crater of the peak is more to be feared than the heat; and
they who seat themselves for a while on the ground find their
clothes corroded. The porphyritic lavas are affected by the action
of the sulphuric acid: the alumine, magnesia, soda, and metallic
oxides gradually disappear; and often nothing remains but the
silex, which unites in mammillary plates, like opal. These
siliceous concretions,* (* Opalartiger kieselsinter. The siliceous
gurh of the volcanoes of the Isle of France contains, according to
Klaproth, 0.72 silex, and 0.21 water; and thus comes near to opal,
which Karsten considers as a hydrated silex.) which M. Cordier
first made known, are similar to those found in the isle of Ischia,
in the extinguished volcanoes of Santa Fiora, and in the Solfatara
of Puzzuoli. It is not easy to form an idea of the origin of these
incrustations. The aqueous vapours, discharged through great
spiracles, do not contain alkali in solution, like the waters of
the Geyser, in Iceland. Perhaps the soda contained in the lavas of
the peak acts an important part in the formation of these deposits
of silex. There may exist in the crater small crevices, the vapours
of which are not of the same nature as those on which travellers,
whose attention has been directed simultaneously to a great number
of objects, have made experiments.
Seated on the northern brink of the crater, I dug a hole of some
inches in depth; and the thermometer placed in this hole rose
rapidly to 42 degrees. Hence we may conclude what must be the heat
in this solfatara at the depth of thirty or forty fathoms. The
sulphur reduced into vapour is condensed into fine crystals, which
however are not equal in size to those M. Dolomieu brought from
Sicily. They are semi-diaphanous octahedrons, very brilliant on the
surface, and of a conchoidal fracture. These masses, which will one
day perhaps be objects of commerce, are constantly bedewed with
sulphurous acid. I had the imprudence to wrap up a few, in order to
preserve them, but I soon discovered that the acid had consumed not
only the paper which contained them, but a part also of my
mineralogical journal. The heat of the vapours, which issue from
the crevices of the caldera, is not sufficiently great to combine
the sulphur while in a state of minute division, with the oxygen of
the atmospheric air; and after the experiment I have just cited on
the temperature of the soil, we may presume that the sulphurous
acid is formed at a certain depth,* in cavities to which the
external air has free access. (* An observer, in general very
accurate, M. Breislack, asserts that the muriatic acid always
predominates in the vapours of Vesuvius. This assertion is contrary
to what M. Gay-Lussac and myself observed, before the great
eruption of 1805, and while the lava was issuing from the crater.
The smell of the sulphurous acid, so easy to distinguish, was
perceptible at a great distance; and when the volcano threw out
scoriae, the smell was mingled with that of petroleum.)
The vapours of heated water, which act on the fragments of lava
scattered about on the caldera, reduce certain parts of it to a
state of paste. On examining, after I had reached America, those
earthy and friable masses, I found crystals of sulphate of alumine.
MM. Davy and Gay-Lussac have already made the ingenious remark,
that two bodies highly inflammable, the metals of soda and potash,
have probably an important part in the action of a volcano; now the
potash necessary to the formation of alum is found not only in
feldspar, mica, pumice-stone, and augite, but also in obsidian.
This last substance is very common at Teneriffe, where it forms the
basis of the tephrinic lava. These analogies between the peak of
Teneriffe and the Solfatara of Puzzuoli, might no doubt be shown to
be more numerous, if the former were more accessible, and had been
frequently visited by naturalists.
An expedition to the summit of the volcano of Teneriffe is
interesting, not solely on account of the great number of phenomena
which are the objects of scientific research; it has still greater
attractions from the picturesque beauties which it lays open to
those who are feelingly alive to the majesty of nature. It is a
difficult task to describe the sensations, which are the more
forcible, inasmuch as they have something undefined, produced by
the immensity of the space as well as by the vastness, the novelty,
and the multitude of the objects, amidst which we find ourselves
transported. When a traveller attempts to describe the loftiest
summits of the globe, the cataracts of the great rivers, the
tortuous valleys of the Andes, he incurs the danger of fatiguing
his readers by the monotonous expression of his admiration. It
appears to me more conformable to the plan I have proposed to
myself in this narrative, to indicate the peculiar character that
distinguishes each zone: we exhibit with more clearness the
physiognomy of the landscape, in proportion as we endeavour to
sketch its individual features, to compare them with each other,
and to discover by this kind of analysis the sources of the
enjoyments, furnished by the great picture of nature.
Travellers have learned by experience, that views from the summits
of very lofty mountains are neither so beautiful, picturesque, nor
so varied, as those from heights which do not exceed that of
Vesuvius, Righi, and the Puy-de-Dome. Colossal mountains, such as
Chimborazo, Antisana, or Mount Rosa, compose so large a mass, that
the plains covered with rich vegetation are seen only in the
immensity of distance, and a blue and vapoury tint is uniformly
spread over the landscape. The peak of Teneriffe, from its slender
form and local position, unites the advantages of less lofty
summits with those peculiar to very great heights. We not only
discern from its top a vast expanse of sea, but we perceive also
the forests of Teneriffe, and the inhabited parts of the coasts, in
a proximity calculated to produce the most beautiful contrasts of
form and colour. We might say, that the volcano overwhelms with its
mass the little island which serves as its base, and it shoots up
from the bosom of the waters to a height three times loftier than
the region where the clouds float in summer. If its crater, half
extinguished for ages past, shot forth flakes of fire like that of
Stromboli in the Aeolian Islands, the peak of Teneriffe, like a
lighthouse, would serve to guide the mariner in a circuit of more
than 260 leagues.
When we were seated on the external edge of the crater, we turned
our eyes towards the north-west, where the coasts are studded with
villages and hamlets. At our feet, masses of vapour, constantly
drifted by the winds, afforded us the most variable spectacle. A
uniform stratum of clouds, similar to that already described, and
which separated us from the lower regions of the island, had been
pierced in several places by the effect of the small currents of
air, which the earth, heated by the sun, began to send towards us.
The port of Orotava, its vessels at anchor, the gardens and the
vineyards encircling the town, shewed themselves through an opening
which seemed to enlarge every instant. From the summit of these
solitary regions our eyes wandered over an inhabited world; we
enjoyed the striking contrast between the bare sides of the peak,
its steep declivities covered with scoriae, its elevated plains
destitute of vegetation, and the smiling aspect of the cultured
country beneath. We beheld the plants divided by zones, as the
temperature of the atmosphere diminished with the elevation of the
site. Below the Piton, lichens begin to cover the scorious and
lustrous lava: a violet,* (* Viola cheiranthifolia.) akin to the
Viola decumbens, rises on the slope of the volcano at 1740 toises
of height; it takes the lead not only of the other herbaceous
plants, but even of the gramina, which, in the Alps and on the
ridge of the Cordilleras, form close neighbourhood with the plants
of the family of the cryptogamia. Tufts of retama, loaded with
flowers, adorn the valleys hollowed out by the torrents, and
encumbered with the effects of the lateral eruptions. Below the
retama, lies the region of ferns, bordered by the tract of the
arborescent heaths. Forests of laurel, rhamnus, and arbutus, divide
the ericas from the rising grounds planted with vines and fruit
trees. A rich carpet of verdure extends from the plain of spartium,
and the zone of the alpine plants even to the groups of the date
tree and the musa, at the feet of which the ocean appears to roll.
I here pass slightly over the principal features of this botanical
chart, as I shall enter hereafter into some farther details
respecting the geography of the plants of the island of Teneriffe.*
(* See below.)
The seeming proximity, in which, from the summit of the peak, we
behold the hamlets, the vineyards, and the gardens on the coast, is
increased by the prodigious transparency of the atmosphere.
Notwithstanding the great distance, we could distinguish not only
the houses, the sails of the vessels, and the trunks of the trees,
but we could discern the vivid colouring of the vegetation of the
plains. These phenomena are owing not only to the height of the
site, but to the peculiar modifications of the air in warm
climates. In every zone, an object placed on a level with the sea,
and viewed in a horizontal direction, appears less luminous, than
when seen from the top of a mountain, where vapours arrive after
passing through strata of air of decreasing density. Differences
equally striking are produced by the influence of climate. The
surface of a lake or large river is less resplendent, when we see
it at an equal distance, from the top of the higher Alps of
Switzerland, than when we view it from the summit of the
Cordilleras of Peru or of Mexico. In proportion as the air is pure
and serene, the solution of the vapours becomes more complete, and
the light loses less in its passage. When from the shores of the
Pacific we ascend the elevated plain of Quito, or that of Antisana,
we are struck for some days by the nearness at which we imagine we
see objects which are actually seven or eight leagues distant. The
peak of Teyde has not the advantage of being situated in the
equinoctial region; but the dryness of the columns of air which
rise perpetually above the neighbouring plains of Africa, and which
the eastern winds convey with rapidity, gives to the atmosphere of
the Canary Islands a transparency which not only surpasses that of
the air of Naples and Sicily, but perhaps exceeds the purity of the
sky of Quito and Peru. This transparency may be regarded as one of
the chief causes of the beauty of landscape scenery in the torrid
zone; it heightens the splendour of the vegetable colouring, and
contributes to the magical effect of its harmonies and contrasts.
If the mass of light, which circulates about objects, fatigues the
external senses during a part of the day, the inhabitant of the
southern climates has his compensation in moral enjoyment. A lucid
clearness in the conceptions, and a serenity of mind, correspond
with the transparency of the surrounding atmosphere. We feel these
impressions without going beyond the boundaries of Europe. I appeal
to travellers who have visited countries rendered famous by the
great creations of the imagination and of art,--the favoured climes
of Italy and Greece.
We prolonged in vain our stay on the summit of the Peak, awaiting
the moment when we might enjoy the view of the whole of the
archipelago of the Fortunate Islands:* we, however, descried Palma,
Gomera, and the Great Canary, at our feet. (* Of all the small
islands of the Canaries, the Rock of the East is the only one which
cannot be seen, even in fine weather, from the top of the Peak. Its
distance is 3 degrees 5 minutes, while that of the Salvage is only
2 degrees 1 minute. The island of Madeira, distant 4 degrees 29
minutes, would be visible, if its mountains were more than 3000
toises high.) The mountains of Lancerota, free from vapours at
sunrise, were soon enveloped in thick clouds. Supposing only an
ordinary refraction, the eye takes in, in calm weather, from the
summit of the volcano, a surface of the globe of 5700 square
leagues, equal to a fourth of the superficies of Spain. The
question has often been agitated, whether it be possible to
perceive the coast of Africa from the top of this colossal pyramid;
but the nearest parts of that coast are still farther from
Teneriffe than 2 degrees 49 minutes, or 56 leagues. The visual ray
of the horizon from the Peak being 1 degree 57 minutes, cape
Bojador can be seen only on the supposition of its height being 200
toises above the level of the ocean. We are ignorant of the height
of the Black Mountains near cape Bojador, as well as of that peak,
called by navigators the Penon Grande, farther to the south of this
promontory. If the summit of the volcano of Teneriffe were more
accessible, we should observe without doubt, in certain states of
the wind, the effects of an extraordinary refraction. On perusing
what Spanish and Portuguese authors relate respecting the existence
of the fabulous isle of San Borondon, or Antilia, we find that it
is particularly the humid wind from west-south-west, which produces
in these latitudes the phenomena of the mirage. We shall not
however admit with M. Vieyra, "that the play of the terrestrial
refractions may render visible to the inhabitants of the Canaries
the islands of Cape Verd, and even the Apalachian mountains of
America."* (* The American fruits, frequently thrown by the sea on
the coasts of the islands of Ferro and Gomera, were formerly
supposed to emanate from the plants of the island of San Borondon.
This island, said to be governed by an archbishop and six bishops,
and which Father Feijoa believed to be the image of the island of
Ferro, reflected on a fog-bank, was ceded in the 16th century, by
the King of Portugal, to Lewis Perdigon, at the time the latter was
preparing to take possession of it by conquest.)
The cold we felt on the top of the Peak, was very considerable for
the season. The centigrade thermometer, at a distance from the
ground, and from the apertures that emitted the hot vapours, fell
in the shade to 2.7 degrees. The wind was west, and consequently
opposite to that which brings to Teneriffe, during a great part of
the year, the warm air that floats above the burning desert of
Africa. As the temperature of the atmosphere, observed at the port
of Orotava by M. Savagi, was 22.8 degrees, the decrement of caloric
was one degree every 94 toises. This result perfectly corresponds
with those obtained by Lamanon and Saussure on the summits of the
Peak and Etna, though in very different seasons. The tall slender
form of these mountains facilitates the means of comparing the
temperature of two strata of the atmosphere, which are nearly in
the same perpendicular plane; and in this point of view the
observations made in an excursion to the volcano of Teneriffe
resemble those of an ascent in a balloon. We must nevertheless
remark, that the ocean, on account of its transparency and
evaporation, reflects less caloric than the plains, into the upper
regions of the air; and also that summits which are surrounded by
the sea are colder in summer, than mountains which rise from a
continent; but this circumstance has very little influence on the
decrement of atmospherical heat; the temperature of the low regions
being equally diminished by the proximity of the ocean.
It is not the same with respect to the influence exercised by the
direction of the wind, and the rapidity of the ascending current;
the latter sometimes increases in an astonishing manner the
temperature of the loftiest mountains. I have seen the thermometer
rise, on the slope of the volcano of Antisana, in the kingdom of
Quito, to 19 degrees, when we were 2837 toises high. M.
Labillardiere has seen it, on the edge of the crater of the peak of
Teneriffe, at 18.7 degrees, though he had used every possible
precaution to avoid the effect of accidental causes.
On the summit of the Peak, we beheld with admiration the azure
colour of the sky. Its intensity at the zenith appeared to
correspond to 41 degrees of the cyanometer. We know, by Saussure's
experiment, that this intensity increases with the rarity of the
air, and that the same instrument marked at the same period 39
degrees at the priory of Chamouni, and 40 degrees at the top of
Mont Blanc. This last mountain is 540 toises higher than the
volcano of Teneriffe; and if, notwithstanding this difference, the
sky is observed there to be of a less deep blue, we must attribute
this phenomenon to the dryness of the African air, and the
proximity of the torrid zone.
We collected on the brink of the crater, some air which we meant to
analyse on our voyage to America. The phial remained so well
corked, that on opening it ten days after, the water rushed in with
impetuosity. Several experiments, made by means of nitrous gas in
the narrow tube of Fontana's eudiometer, seemed to prove that the
air of the crater contained 0.09 degrees less oxygen than the air
of the sea; but I have little confidence in this result obtained by
means which we now consider as very inexact. The crater of the Peak
has so little depth, and the air is renewed with so much facility,
that it is scarcely probable the quantity of azote is greater there
than on the coasts. We know also, from the experiments of MM.
Gay-Lussac and Theodore de Saussure, that in the highest as well as
in the lowest regions of the atmosphere, the air equally contains
0.21 of oxygen.* (* During the stay of M. Gay-Lussac and myself at
the hospice of Mont Cenis, in March 1805, we collected air in the
midst of a cloud loaded with electricity. This air, analysed in
Volta's eudiometer, contained no hydrogen, and its purity did not
differ 0.002 of oxygen from the air of Paris, which we had carried
with us in phials hermetically sealed.)
We saw on the summit of the Peak no trace of psora, lecidea, or
other cryptogamous plants; no insect fluttered in the air. We found
however a few hymenoptera adhering to masses of sulphur moistened
with sulphurous acid, and lining the mouths of the funnels. These
are bees, which appear to have been attracted by the flowers of the
Spartium nubigenum, and which oblique currents of air had carried
up to these high regions, like the butterflies found by M. Ramond
at the top of Mont Perdu. The butterflies perished from cold, while
the bees on the Peak were scorched on imprudently approaching the
crevices where they came in search of warmth.