Personal Narrative of Travels to the Equinoctial Regions of America, During the Years 1799-1804, Vol.2 — Chapter 2.17, Part 2

Such are the successions of rocks, which I described on the spot as I progressively found them, from the lake of Tacarigua to the entrance of the steppes.

Few places in Europe display a geological arrangement so well worthy of being studied.

We saw there in succession six formations: namely, mica-slate-gneiss, green transition-slate, black transition-limestone, serpentine and grunstein, amygdaloid (with pyroxene), and phonolite.

I must observe, in the first place, that the substance just described under the name of grunstein, in every respect resembles that which forms layers in the mica-slate of Cabo Blanco, and veins near Caracas.

It differs only by containing neither quartz, garnets, nor pyrites.

The close relations we observed near the Cerro de Chacao, between the grunstein and the serpentine, cannot surprise these geologists who have studied the mountains of Franconia and Silesia.

Near Zobtenberg* (* Between Tampadel and Silsterwiz.

) a serpentine rock alternates also with gabbro.

In the district of Glatz the fissures of the gabbro are filled with a steatite of a greenish white colour, and the rock which was long thought to belong to the grunsteins* is a close mixture of feldspar and diallage.

(* In the mountains of Bareuth, in Franconia, so abundant in grunstein and serpentine, these formations are not connected together.

The serpentine there belongs rather to the schistose hornblende (hornblendschiefer), as in the island of Cuba.

Near Guanaxuato, in Mexico, I saw it alternating with syenite.

These phenomena of serpentine rocks forming layers in eurite (weisstein), in schistose hornblende, in gabbro, and in syenite, are so much the more remarkable, as the great mass of garnetiferous serpentines, which are found in the mountains of gneiss and mica-slate, form little distinct mounts, masses not covered by other formations.

It is not the same in the mixtures of serpentine and granulated limestone.

) The grunsteins of Tucutunemo, which we consider as constituting the same formation as the serpentine rock, contain veins of malachite and copper-pyrites.

These same metalliferous combinations are found also in Franconia, in the grunsteins of the mountains of Steben and Lichtenberg.

With respect to the green slates of Malpaso, which have all the characters of transition-slates, they are identical with those which M. von Buch has so well described, near Schonau, in Silesia.

They contain beds of grunstein, like the slates of the mountains of Steben just mentioned.

* (* On advancing into the adit for draining the Friedrich-Wilhelmstollen mine, which I caused to be begun in 1794, near Steben, and which is yet only 340 toises long, there have successively been found, in the transition-slate subordinate strata of pure and porphyritic grunstein, strata, of Lydian stone and ampelite (alaunschiefer), and strata of fine-grained grunstein.

All these strata characterise the transition-slates.

) The black limestone of the Morros de San Juan is also a transition-limestone.

It forms perhaps a subordinate stratum in the slates of Malpaso.

This situation would be analogous to what is observed in several parts of Switzerland.

* (* For Instance, at the Glyshorn, at the Col de Balme, etc. ) The slaty zone, the centre of which is the ravine of Piedras Azules, appears divided into two formations.

On some points we think we observe one passing into the other.

The grunsteins, which begin again to the south of these slates, appear to me to differ little from those found north of the ravine of Piedras Azules.

I did not see there any pyroxene; but on the very spot I recognized a number of crystals in the amygdaloid, which appears so strongly linked to the grunstein that they alternate several times.

The geologist may consider his task as fulfilled when he has traced with accuracy the positions of the diverse strata; and has pointed out the analogies traceable between these positions and what has been observed in other countries.

But how can he avoid being tempted to go back to the origin of so many different substances, and to inquire how far the dominion of fire has extended in the mountains that bound the great basin of the steppes?

In researches on the position of rocks we have generally to complain of not sufficiently perceiving the connection between the masses, which we believe to be superimposed on one another.

Here the difficulty seems to arise from the too intimate and too numerous relations observed in rocks that are thought not to belong to the same family.

The phonolite (or leucostine compacte of Cordier) is pretty generally regarded by all who have at once examined burning and extinguished volcanoes, as a flow of lithoid lava.

I found no real basalt or dolerite; but the presence of pyroxene in the amygdaloid of Parapara leaves little doubt of the igneous origin of those spheroidal masses, fissured, and full of cavities.

Balls of this amygdaloid are enclosed in the grunstein; and this grunstein alternates on one side with a green slate, on the other with the serpentine of Tucutunemo.

Here, then, is a connexion sufficiently close established between the phonolites and the green slates, between the pyroxenic amygdaloids and the serpentines containing copper-ores, between volcanic substances and others that are included under the vague name of transition-traps.

All these masses are destitute of quartz like the real trap-porphyries, or volcanic trachytes.

This phenomenon is the more remarkable, as the grunsteins which are called primitive almost always contain quartz in Europe.

The most general dip of the slates of Piedras Azules, of the grunsteins of Parapara, and of the pyroxenic amygdaloids embedded in strata of grunstein, does not follow the slope of the ground from north to south, but is pretty regular towards the north.

The strata incline towards the chain of the coast, as substances which had not been in fusion might be supposed to do.

Can we admit that so many alternating rocks, imbedded one in the other, have a common origin?

The nature of the phonolites, which are lithoid lavas with a feldspar basis, and the nature of the green slates intermixed with hornblende, oppose this opinion.

In this state of things we may choose between two solutions of the problem in question.

In one of these solutions the phonolite of the Cerro de Flores is to be regarded as the sole volcanic production of the tract; and we are forced to unite the pyroxenic amygdaloids with the rest of the grunsteins, in one single formation, that which is so common in the transition-mountains of Europe, considered hitherto as not volcanic.

In the other solution of the problem, the masses of phonolite, amygdaloid, and grunstein, which are found in the south of the ravine of Piedras Azules, are separated from the grunsteins and serpentine rocks that cover the declivity of the mountains north of the ravine.

In the present state of knowledge I find difficulties almost equally great in adopting either of these suppositions; but I have no doubt that, when the real grunsteins (not the hornblende-grunsteins) contained in the gneiss and mica-slates, shall have been more attentively examined in other places; when the basalts (with pyroxene) forming strata in primitive rocks* (* For instance, at Krobsdorf, in Silesia, a stratum of basalt has been recognized in the mica-slate by two celebrated geologists, MM.

von Buch and Raumer.

(Vom Granite des Riesengebirges, 1813. ) and the diabases and amygdaloids in the transition mountains, shall have been carefully studied; when the texture of the masses shall have been subjected to a kind of mechanical analysis, and the hornblendes better distinguished from the pyroxenes,* (* The grunsteins or diabases of the Fichtelgebirge, in Franconia, which belong to the transition-slate, sometimes contain pyroxenes.

) and the grunsteins from the dolerites; a great number of phenomena which now appear isolated and obscure, will be ranged under general laws.

The phonolite and other rocks of igneous origin at Parapara are so much the more interesting, as they indicate ancient eruptions in a granite zone; as they belong to the shore of the basin of the steppes, as the basalts of Harutsh belong to the shore of the desert of Sahara; and lastly, as they are the only rocks of the kind we observed in the mountains of the Capitania-General of Caracas, which are also destitute of trachytes or trap-porphyry, basalts, and volcanic productions.

* (* From the Rio Negro to the coasts of Cumana and Caracas, to the east of the mountains of Merida, which we did not visit.

) The southern declivity of the western chain is tolerably steep; the steppes, according to my barometrical measurements, being a thousand feet lower than the bottom of the basin of Aragua.

From the extensive table-land of the Villa de Cura we descended towards the banks of the Rio Tucutunemo, which has hollowed for itself, in a serpentine rock, a longitudinal valley running from east to west, at nearly the same level as La Victoria.

A transverse valley, lying generally north and south, led us into the Llanos, by the villages of Parapara and Ortiz.

It grows very narrow in several parts.

Basins, the bottoms of which are perfectly horizontal, communicate together by narrow passes with steep declivities.

They were, no doubt, formerly small lakes, which, owing to the accumulation of the waters, or some more violent catastrophe, have broken down the dykes by which they were separated.

This phenomenon is found in both continents, wherever we examine the longitudinal valleys forming the passages of the Andes, the Alps,* (* For example, the road from the valley of Ursern to the Hospice of St. Gothard, and thence to Airolo.

) or the Pyrenees.

It is probable, that the irruption of the waters towards the Llanos have given, by extraordinary rents, the form of ruins to the Morros of San Juan and of San Sebastian.

The volcanic tract of Parapara and Ortis is now only 30 or 40 toises above the Llanos.

The eruptions consequently took place at the lowest point of the granitic chain.

In the Mesa de Paja, in the ninth degree of latitude, we entered the basin of the Llanos.

The sun was almost at its zenith; the earth, wherever it appeared sterile and destitute of vegetation, was at the temperature of 48 or 50 degrees.

* (* A thermometer, placed in the sand, rose to 38. 4 and 40 degrees Reaumur.

) Not a breath of air was felt at the height at which we were on our mules; yet, in the midst of this apparent calm, whirls of dust incessantly arose, driven on by those small currents of air which glide only over the surface of the ground, and are occasioned by the difference of temperature between the naked sand and the spots covered with grass.

These sand-winds augment the suffocating heat of the air.

Every grain of quartz, hotter than the surrounding air, radiates heat in every direction; and it is difficult to observe the temperature of the atmosphere, owing to these particles of sand striking against the bulb of the thermometer.

All around us the plains seemed to ascend to the sky, and the vast and profound solitude appeared like an ocean covered with sea-weed.

According to the unequal mass of vapours diffused through the atmosphere, and the variable decrement in the temperature of the different strata of air, the horizon in some parts was clear and distinct; in other parts it appeared undulating, sinuous, and as if striped.

The earth there was confounded with the sky.

Through the dry mist and strata of vapour the trunks of palm-trees were seen from afar, stripped of their foliage and their verdant summits, and looking like the masts of a ship descried upon the horizon.

There is something awful, as well as sad and gloomy, in the uniform aspect of these steppes.

Everything seems motionless; scarcely does a small cloud, passing across the zenith, and denoting the approach of the rainy season, cast its shadow on the earth.

I know not whether the first aspect of the Llanos excite less astonishment than that of the chain of the Andes.

Mountainous countries, whatever may be the absolute elevation of the highest summits, have an analogous physiognomy; but we accustom ourselves with difficulty to the view of the Llanos of Venezuela and Casanare, to that of the Pampas of Buenos Ayres and of Chaco, which recal to mind incessantly, and during journeys of twenty or thirty days, the smooth surface of the ocean.

I

had seen the plains or llanos of La Mancha in Spain, and the heaths (ericeta) that extend from the extremity of Jutland, through Luneburg and Westphalia, to Belgium.

These last are really steppes, and, during several ages, only small portions of them have yielded to cultivation;

but the plains of the west and north of Europe present only a feeble image of the immense llanos of South America.

It is in the south-east of our continent, in Hungary, between the Danube and the Theiss; in Russia, between the Borysthenes, the Don, and the Volga, that we find those vast pastures, which seem to have been levelled by a long abode of the waters, and which meet the horizon on every side.

The plains of Hungary, where I traversed them on the frontiers of Germany, between Presburg and Oedenburg, strike the imagination of the traveller by the constant mirage; but their greatest extent is more to the east, between Czegled, Debreczin, and Tittel.

There they present the appearance of a vast ocean of verdure, having only two outlets, one near Gran and Waitzen, the other between Belgrade and Widdin.

The different quarters of the world have been supposed to be characterized by the remark, that Europe has its heaths, Asia its steppes, Africa its deserts, and America its savannahs; but by this distinction, contrasts are established that are not founded either on the nature of things, or the genius of languages.

The existence of a heath always supposes an association of plants of the family of ericae; the steppes of Asia are not everywhere covered with saline plants; the savannahs of Venezuela furnish not only the gramina, but with them small herbaceous mimosas, legumina, and other dicotyledonous plants.

The plains of Songaria, those which extend between the Don and the Volga, and the puszta of Hungary, are real savannahs, pasturages abounding in grasses;* (* These vast steppes of Hungary are elevated only thirty or forty toises above the level of the sea, which is more than eighty leagues distant from them.

See Wahlenberg's Flora Carpathianica.

Baron Podmanitzky, an Hungarian nobleman, highly distinguished for his knowledge of the physical sciences, caused the level of these plains to be taken, to facilitate the formation of a canal then projected between the Danube and the Theiss.

He found the line of division, or the convexity of the ground, which slopes on each side towards the beds of the two rivers, to be only thirteen toises above the height of the Danube.

The widely extended pastures, which reach in every direction to the horizon, are called in the country, Puszta, and, over a distance of many leagues, are without any human habitation.

Plains of this kind, intermingled with marshes and sandy tracts, are found on the western side of the Theiss, between Czegled, Csaba, Komloss, and Szarwass; and on the eastern side, between Debreczin, Karczag, and Szoboszlo.

The area of these plains of the interior basin of Hungary has been estimated, by a pretty accurate calculation, to be between two thousand five hundred and three thousand square leagues (twenty to a degree).

Between Czegled, Szolnok, and Ketskemet, the plain resembles a sea of sand.

) while the savannahs to the east and west of the Rocky Mountains and of New Mexico produce chenopodiums containing carbonate and muriate of soda.

Asia has real deserts destitute of vegetation, in Arabia, in Gobi, and in Persia.

Since we have become better acquainted with the deserts in the interior of Africa, so long and so vaguely confounded together under the name of desert of Sahara (Zahra); it has been observed, that in this continent, towards the east, savannahs and pastures are found, as in Arabia, situated in the midst of naked and barren tracts.

It is these deserts, covered with gravel and destitute of plants, which are almost entirely wanting in the New World.

I saw them only in that part of Peru, between Amotape and Coquimbo, on the shores of the Pacific.

These are called by the Spaniards, not llanos, but the desiertos of Sechura and Atacamez.

This solitary tract is not broad, but it is four hundred and forty leagues long.

The rock pierces everywhere through the quicksands.

No drop of rain ever falls on it; and, like the desert of Sahara, north of Timbuctoo, the Peruvian desert affords, near Huaura, a rich mine of native salt.

Everywhere else, in the New World, there are plains desert because not inhabited, but no real deserts.

* (* We are almost tempted, however, to give the name of desert to that vast and sandy table-land of Brazil, the Campos dos Parecis, which gives birth to the rivers Tapajos, Paraguay, and Madeira, and which reaches the summit of the highest mountains.

Almost destitute of vegetation, it reminds us of Gobi, in Mongolia.

) The same phenomena are repeated in the most distant regions; and, instead of designating those vast treeless plains in accordance with the nature of the plants they produce, it seems natural to class them into deserts, steppes, or savannahs; into bare lands without any appearance of vegetation, and lands covered with gramina or small plants of the dicotyledonous tribe.

The savannahs of America, especially those of the temperate zone, have in many works been designated by the French term prairies; but this appears to me little applicable to pastures which are often very dry, though covered with grass of four or five feet in height.

The Llanos and the Pampas of South America are really steppes.

They are covered with beautiful verdure in the rainy season, but in the time of great drought they assume the aspect of a desert.

The grass is then reduced to powder;

the earth cracks; the alligators and the great serpents remain buried in the dried mud, till awakened from their long lethargy by the first showers of spring.

These phenomena are observed on barren tracts of fifty or sixty leagues in length, wherever the savannahs are not traversed by rivers; for on the borders of rivulets, and around little pools of stagnant water, the traveller finds at certain distances, even during the period of the great droughts, thickets of mauritia, a palm, the leaves of which spread out like a fan, and preserve a brilliant verdure.

The steppes of Asia are all beyond the tropics, and form very elevated table-lands.

America also has savannahs of considerable extent on the backs of the mountains of Mexico, Peru, and Quito; but its most extensive steppes, the Llanos of Cumana, Caracas, and Meta, are little raised above the level of the ocean, and all belong to the equinoctial zone.

These circumstances give them a peculiar character.

They have not, like the steppes of southern Asia, and the deserts of Persia, those lakes without issue, those small systems of rivers which lose themselves either in the sands, or by subterranean filtrations.

The Llanos of America incline to the east and south; and their running waters are branches of the Orinoco.

The course of these rivers once led me to believe, that the plains formed table-lands, raised at least from one hundred to one hundred and fifty toises above the level of the ocean.

I supposed that the deserts of interior Africa were also at a considerable height; and that they rose one above another as in tiers, from the coast to the interior of the continent.

No barometer has yet been carried into the Sahara.

With respect to the Llanos of America, I found by barometric heights observed at Calabozo, at the Villa del Pao, and at the mouth of the Meta, that their height is only forty or fifty toises above the level of the sea.

The fall of the rivers is extremely gentle, often nearly imperceptible; and therefore the least wind, or the swelling of the Orinoco, causes a reflux in those rivers that flow into it.

The Indians believe themselves to be descending during a whole day, when navigating from the mouths of these rivers to their sources.

The descending waters are separated from those that flow back by a great body of stagnant water, in which, the equilibrium being disturbed, whirlpools are formed very dangerous for boats.

The chief characteristic of the savannahs or steppes of South America is the absolute want of hills and inequalities--the perfect level of every part of the soil.

Accordingly the Spanish conquerors, who first penetrated from Coro to the banks of the Apure, did not call them deserts or savannahs, or meadows, but plains (llanos).

Often within a distance of thirty square leagues there is not an eminence of a foot high.

This resemblance to the surface of the sea strikes the imagination most powerfully where the plains are altogether destitute of palm-trees; and where the mountains of the shore and of the Orinoco are so distant that they cannot be seen, as in the Mesa de Pavones.

A

person would be tempted there to take the altitude of the sun with a quadrant, if the horizon of the land were not constantly misty on account of the variable effects of refraction.

This equality of surface is still more perfect in the meridian of Calabozo, than towards the east, between Cari, La Villa del Pao, and Nueva Barcelona;

but it extends without interruption from the mouths of the Orinoco to La Villa de Araure and to Ospinos, on a parallel of a hundred and eighty leagues in length; and from San Carlos to the savannahs of Caqueat, on a meridian of two hundred leagues.

It particularly characterises the New Continent, as it does the low steppes of Asia, between the Borysthenes and the Volga, between the Irtish and the Obi.

The deserts of central Africa, of Arabia, Syria, and Persia, Gobi, and Casna, present, on the contrary, many inequalities, ranges of hills, ravines without water, and rocks which pierce the sands.

The Llanos, however, notwithstanding the apparent uniformity of their surface, present two kinds of inequalities, which cannot escape the observation of the traveller.

The first is known by the name of banks (bancos); they are in reality shoals in the basin of the steppes, fractured strata of sandstone, or compact limestone, standing four or five feet higher than the rest of the plain.

These banks are sometimes three or four leagues in length; they are entirely smooth, with a horizontal surface; their existence is perceived only by examining their margins.

The second species of inequality can be recognised only by geodesical or barometric levellings, or by the course of rivers.

It is called a mesa or table, and is composed of small flats, or rather convex eminences, that rise insensibly to the height of a few toises.

Such are, towards the east, in the province of Cumana, on the north of the Villa de la Merced and Candelaria, the Mesas of Amana, of Guanipa, and of Jonoro, the direction of which is south-west and north-east;

and which, in spite of their inconsiderable elevation, divide the waters between the Orinoco and the northern coast of Terra Firma.

The convexity of the savannah alone occasions this partition: we there find the dividing of the waters (divortia aquarum* (* "C. Manlium prope jugis [Tauri] ad divortia aquarum castra posuisse."

Livy lib.

38 c.

75. )), as in Poland, where, far from the Carpathian mountains, the plain itself divides the waters between the Baltic and the Black Sea.

Geographers, who suppose the existence of a chain of mountains wherever there is a line of division, have not failed to mark one in the maps, at the sources of the Rio Neveri, the Unare, the Guarapiche, and the Pao.

Thus the priests of Mongol race, according to ancient and superstitious custom, erect oboes, or little mounds of stone, on every point where the rivers flow in an opposite direction.

The uniform landscape of the Llanos; the extremely small number of their inhabitants; the fatigue of travelling beneath a burning sky, and an atmosphere darkened by dust; the view of that horizon, which seems for ever to fly before us; those lonely trunks of palm-trees, which have all the same aspect, and which we despair of reaching, because they are confounded with other trunks that rise by degrees on the visual horizon; all these causes combine to make the steppes appear far more extensive than they are in reality.

The planters who inhabit the southern declivity of the chain of the coast see the steppes extend towards the south, as far as the eye can reach, like an ocean of verdure.

They know that from the Delta of the Orinoco to the province of Varinas, and thence, by traversing the banks of the Meta, the Guaviare, and the Caguan, they can advance three hundred and eighty leagues* (* This is the distance from Timbuctoo to the northern coast of Africa.

) into the plains, first from east to west, and then from north-east to south-east beyond the Equator, to the foot of the Andes of Pasto.

They know by the accounts of travellers the Pampas of Buenos Ayres, which are also Llanos covered with fine grass, destitute of trees, and filled with oxen and horses become wild.

They suppose that, according to the greater part of our maps of America, this continent has only one chain of mountains, that of the Andes, which stretches from south to north; and they form a vague idea of the contiguity of all the plains from the Orinoco and the Apure to the Rio de la Plata and the Straits of Magellan.