Personal Narrative of Travels to the Equinoctial Regions of America, During the Years 1799-1804, Vol.3 — 44 - Chapter 3.32, Part 14

9. SANDSTONE OF THE BERGANTIN.

Between Nueva Barcelona and the Cerro del Bergantin a quartzose sandstone covers the Jura limestone of Cumanacoa.

Is it an arenaceous rock analogous to green sandstone, or does it belong to the sandstone of Cocollar?

In the latter case its presence seems to prove still more clearly that the limestones of Cumanacoa and Caripe are only two parts of the same system, alternating with sandstone, sometimes quartzose, sometimes slaty.

10. GYPSUM OF THE LLANOS OF VENEZUELA.

Deposits of lamellar gypsum, containing numerous strata of marl, are found in patches on the steppes of Caracas and Barcelona; for instance, in the table-land of San Diego, between Ortiz and the Mesa de Paja; and near the mission of Cachipo.

They appeared to me to cover the Jura limestone of Tisnao, which is analogous to that of Caripe, where we find it mixed with masses of fibrous gypsum.

I have not given the name formation either to the sandstone of the Orinoco, of Cocollar, of Bergantin or to the gypsum of the Llanos, because nothing as yet proves the independence of those arenaceous and gypsous soils.

I think it will one day be ascertained that the gypsum of the Llanos covers not only the Jura limestone of the Llanos, but that it is sometimes enclosed in it like the gypsum of the Golfo Triste on the east of the Alpine limestone of Cumanacoa.

The great masses of sulphur found in the layers, almost entirely clayey, of the steppes (at Guayuta, valley of San Bonifacio, Buen Pastor, confluence of the Rio Pao with the Orinoco) may possibly belong to the marl of the gypsum of Ortiz.

These clayey beds are more worthy of attention since the interesting observations of Von Buch and several other celebrated geologists respecting the cavernosity of gypsum, the irregularity of the inclination of its strata and its parallel position with the two declivities of the Hartz and the upheaved chain of the Alps; while the simultaneous presence of sulphur, oligist iron and the sulphurous acid vapours which precede the formation of sulphuric acid, seem to manifest the action of forces placed at a great depth in the interior of the globe.

11. FORMATION OF MURIATIFEROUS CLAY (WITH BITUMEN AND LAMELLAR GYPSUM) OF THE PENINSULA OF

ARAYA.

This soil presents a striking analogy with salzthon or leberstein (muriatiferous clay) which I have found accompanying gem-salt in every zone.

In the salt-pits of Araya (Haraia) it attracted the attention of Peter Martyr d'Anghiera at the beginning of the sixteenth century.

It probably facilitated the rupture of the earth and the formation of the gulf of Cariaco.

This clay is of a smoky colour, impregnated with petroleum, mingled with lamellar and lenticular gypsum and sometimes traversed by small veins of fibrous gypsum.

It incloses angular and less friable masses of dark brown clay with a slaty and sometimes conchoidal fracture.

Muriate of soda is found in particles invisible to the naked eye.

The relations of position or superposition between this soil and the tertiary rocks does not appear sufficiently clear to enable me to pronounce with certainty on this element, the most important of positive geology.

The co-ordinate layers of gem-salt, muriatiferous clay and gypsum present the same difficulties in both hemispheres; these masses, the forms of which are very irregular, everywhere exhibit traces of great commotions.

They are scarcely ever covered by independent formations; and after having been long believed, in Europe, that gem-salt was exclusively peculiar to Alpine and transition limestone, it is now still more generally admitted, either from reasoning founded on analogy or from suppositions on the prolongation of the strata, that the true location of gem-salt is found in variegated sandstone (buntersandstein).

Sometimes gem-salt appears to oscillate between variegated sandstone and muschelkalk.

I made two excursions on the peninsula of Araya.

In the first I was inclined to consider the muriatiferous clay as subordinate to the conglomerate (evidently of tertiary formation) of the Barigon and of the mountain of the castle of Cumana, because a little to the north of that castle I had found shelves of hardened clay containing lamellar gypsum inclosed in the tertiary strata.

I believed that the muriatiferous clay might alternate with the calcareous conglomerate of Barigon; and near the fishermen's huts situated opposite Macanao, conglomerate rocks appeared to me to pierce through the strata of clay.

During a second excursion to Maniquarez and the aluminiferous slates of Chaparuparu, the connexion between tertiary strata and bituminous clay seemed to me somewhat problematical.

I examined more particularly the Penas Negras near the Cerro de la Vela, east-south-east of the ruined castle of Araya.

The limestone of the Penas is compact, bluish grey and almost destitute of petrifactions.

It appeared to me to be much more ancient than the tertiary conglomerate of Barigon, and I saw it covering, in concordant position, a slaty clay, somewhat analogous to muriatiferous clay.

I

was greatly interested in comparing this latter formation with the strata of carburetted marl contained in the Alpine limestone of Cumanacoa.

According to the opinions now most generally received, the rock of the Penas Negras may be considered as representing muschelkalk (limestone of Gottingen); and the saliferous and bituminous clay of Araya, as representing variegated sandstone; but these problems can only be solved when the mines of those countries are worked.

Those geologists who are of opinion that the gem-salt of Italy penetrates into a stratum above the Jura limestone, and even the chalk, may be led to mistake the limestone of the Penas Negras for one of the strata of compact limestone without grains of quartz and petrifactions, which are frequently found amidst the tertiary conglomerate of Barigon and of the Castillo de Cumana; the saliferous clay of Araya would appear to them analogous to the plastic clay of Paris,* (* Tertiary sandstone with lignites, or molassus of Argovia.

) or to the clayey shelves (dief et tourtia) of secondary sandstone with lignites, containing salt-springs, in Belgium and Westphalia.

However difficult it may be to distinguish separately the strata of marl and clay belonging to variegated sandstone, muschelkalk, quadersandstein, Jura limestone, secondary sandstone with lignites (green and iron sand) and the tertiary strata lying above chalk, I believe that the bitumen which everywhere accompanies gem-salt, and most frequently salt-springs, characterizes the muriatiferous clay of the peninsula of Araya and the island of Marguerita, as linked with formations lying below the tertiary strata.

I do not say that they are anterior to that formation, for since the publication of M. von Buch's observations on the Tyrol, we must no longer consider what is below, in space, as necessarily anterior, relatively to the epoch of its formation.

Bitumen and petroleum still issue from the mica-slate; these substances are ejected whenever the soil is shaken by a subterranean force (between Cumana, Cariaco and the Golfo Triste).

Now, in the peninsula of Araya, and in the island of Marguerita, saliferous clay impregnated with bitumen is met with in connexion with this early formation, nearly as gem-salt appears in Calabria in flakes, in basins inclosed in strata of granite and gneiss.

Do these circumstances serve to support that ingenious system, according to which all the co-ordinate formations of gypsum, sulphur, bitumen and gem-salt (constantly anhydrous) result from floods passing across the crevices which have traversed the oxidated crust of our planet, and penetrating to the seat of volcanic action.

The enormous masses of muriate of soda recently thrown up by Vesuvius,* (* The ejected masses in 1822 were so considerable that the inhabitants of some villages round Vesuvius collected them for domestic purposes.

) the small veins of that salt which I have often seen traverse the most recently ejected lavas, and of which the origin (by sublimation) appears similar to that of oligist iron deposited in the same vents,* (* Gay-Lussac on the action of volcanoes in the Annales de Chimie volume 22 page 418. ) the layers of gem-salt and saliferous clay of the trachytic soil in the plains of Peru and around the volcano of the Andes of Quito are well worthy the attention of geologists who would discuss the origin of formations.

In the present sketch I confine myself to the mere enumeration of the phenomena of position, indicating, at the same time, some theoretic views, by which observers in more advantageous circumstances than I was myself may direct their researches.

12. AGGLOMERATE LIMESTONE OF THE BARIGON, OF THE CASTLE OF CUMANA, AND OF THE VICINITY OF PORTO CABELLO.

This is a very complex formation, presenting that mixture and that periodical return of compact limestone, quartzose sandstone and conglomerates (limestone breccia) which in every zone peculiarly characterises the tertiary strata.

It forms the mountain of the castle of San Antonio near the town of Cumana, the south-west extremity of the peninsula of Araya, the Cerro Meapire, south of Caraco and the vicinity of Porto Cabello.

It contains (1) a compact limestone, generally of a whitish grey, or yellowish white (Cerro del Barigon), some very thin layers of which are entirely destitute of petrifactions, while others are filled with cardites, ostracites, pectens and vestiges of lithophyte polypi: (2) a breccia in which an innumerable number of pelagic shells are found mixed with grains of quartz agglutinated by a cement of carbonate of lime: (3) a calcareous sandstone with very fine rounded grains of quartz (Punta Arenas, west of the village of Maniquarez) and containing masses of brown iron ore: (4) banks of marl and slaty clay, containing no spangles of mica, but enclosing selenite and lamellar gypsum.

These banks of clay appeared to me constantly to form the lower strata.

There also belongs to this tertiary stratum the limestone tufa (fresh-water formation) of the valleys of Aragua near Vittoria, and the fragmentary rock of Cabo Blanco, westward of the port of La Guayra.

I must not designate the latter by the name of nagelfluhe, because that term indicates rounded fragments, while the fragments of Cabo Blanco are generally angular, and composed of gneiss, hyaline quartz and chloritic slate, joined by a limestone cement.

This cement contains magnetic sand,* (* This magnetic sand no doubt owes its origin to chloritous slate, which, in these latitudes, forms the bed of the sea.

) madrepores, and vestiges of bivalve sea shells.

The different fragments of tertiary strata which I found in the littoral Cordillera of Venezuela, on the two slopes of the northern chain, seem to be superposed near Cumana (between Bordones and Punta Delgada); in the Cerro of Meapire; on the [Alpine] limestone of Cumanacoa; between Porto Cabello and the Rio Guayguaza; as well as in the valleys of Aragua; on granite; on the western declivity of the hill formed by Cabo Blanco, on gneiss; and in the peninsula of Araya, on saliferous clay.

But this is perhaps merely the effect of apposition.

* (* An-nicht Auflagerung, according to the precise language of the geologists of my country.

) If we would range the different members of the tertiary series according to the age of their formation we ought, I believe, to regard the breccia of Cabo Blanco with fragments of primitive rocks as the most ancient, and make it be succeeded by the arenaceous limestone of the castle of Cumana, without horned silex, yet somewhat analogous to the coarse limestone of Paris, and the fresh-water soil of Victoria.

The clayey gypsum, mixed with calcareous breccia with madrepores, cardites and oysters, which I found between Carthagena and the Cerro de la Popa, and the equally recent limestones of Guadalope and Barbadoes (limestones filled with seashells resembling those now existing in the Caribbean Sea) prove that the latest deposited strata of the tertiary formation extend far towards the west and north.

These recent formations, so rich in vestiges of organized bodies, furnish a vast field of observation to those who are familiar with the zoological character of rocks.

To examine these vestiges in strata superposed as by steps, one above another, is to study the Fauna of different ages and to compare them together.

The geography of animals marks out limits in space, according to the diversity of climates, which determine the actual state of vegetation on our planet.

The geology of organized bodies, on the contrary, is a fragment of the history of nature, taking the word history in its proper acceptation: it describes the inhabitants of the earth according to succession of time.

We may study genera and species in museums, but the Fauna of different ages, the predominance of certain shells, the numerical relations which characterize the animal kingdom and the vegetation of a place or of a period, should be studied in sight of those formations.

It has long appeared to me that in the tropics as well as in the temperate zone the species of univalve shells are much more numerous than bivalves.

From this superiority in number the organic fossil world furnishes, in every latitude, a further analogy with the intertropical shells that now live at the bottom of the ocean.

In fact, M. Defrance, in a work* full of new and ingenious ideas, not only recognizes this preponderance of the univalves in the number of the species, but also observes that out of 5500 fossil univalve, bivalve and multivalve shells, contained in his rich collections, there are 3066 univalve, 2108 bivalve, and 326 multivalve; the univalve fossils are therefore to the bivalve as three to two.

(* Table of Organized Fossil Bodies, 1824. ) 13. FORMATION OF PYROXENIC AMYGDALOID AND PHONOLITE, BETWEEN ORTIZ AND CERRO DE FLORES.

I place pyroxenic amygdaloid and phonolite (porphyrschiefer) at the end of the formations of Venezuela, not as being the only rocks which I consider as pyrogenous, but as those of which the volcanic origin is probably posterior to the tertiary strata.

This conclusion is not deduced from the observations I made at the southern declivity of the littoral Cordillera, between the Morros of San Juan, Parapara and the Llanos of Calabozo.

In that region local circumstances would possibly lead us to regard the amygdaloids of Ortiz as linked to a system of transition rocks (amphibolic serpentine, diorite, and carburetted slate of Malpasso); but the eruption of the trachytes across rocks posterior to the chalk (in the Euganean Mountains and other parts of Europe) joined to the phenomenon of total absence of fragments of pyroxenic porphyry, trachyte, basalt and phonolite (The fragments of these rocks appear only in tufas or conglomerates which belong essentially to basaltic formations or surround the most recent volcanoes.

Every volcanic formation is enveloped in breccia, which is the effect of the eruption itself.

), in the conglomerates or fragmentary rocks anterior to the recent tertiary strata, renders it probable that the appearance of trap rocks at the surface of the earth is the effect of one of the last revolutions of our planet, even where the eruption has taken place by crevices (veins) which cross gneiss-granite, or the transition rocks not covered by secondary and tertiary formations.

The small volcanic stratum of Ortiz (latitude 9 degrees 28 minutes to 9 degrees 36 minutes) formed the ancient shore of the vast basin of the Llanos of Venezuela: it is composed on the points where I could examine it of only two kinds of rocks, namely, amygdaloid and phonolite.

The greyish blue amygdaloid contains fendilated crystals of pyroxene and mesotype.

It forms balls with concentric layers of which the flattened centre is nearly as hard as basalt.

Neither olivine nor amphibole can be distinguished.

Before it shows itself as a separate stratum, rising in small conic hills, the amygdaloid seems to alternate by layers with the diorite, which we have mentioned above as mixed with carburetted slate and amphibolic serpentine.

These close relations of rocks so different in appearance and so likely to embarrass the observer give great interest to the vicinity of Ortiz.

If the masses of diorite and amygdaloid, which appear to us to be layers, are very large veins, they may be supposed to have been formed and upheaved simultaneously.

We are now acquainted with two formations of amygdaloid; one, the most common, is subordinate to the basalt: the other, much more rare,* (* We find examples of the latter in Norway (Vardekullen, near Skeen), in the mountains of the Thuringerwald; in South Tyrol; at Hefeld in the Hartz, at Bolanos in Mexico etc. ) belongs to the pyroxenic porphyry.

* (* Black porphyries of M. von Buch.

) The amygdaloid of Ortiz approaches, by its oryctognostic characters, to the former of those formations, and we are almost surprised to find it joining, not basalt, but phonolite,* an eminently felspathic rock, in which we find some crystals of amphibole, but pyroxene very rarely, and never any olivine.

(* There are phonolites of basaltic strata (the most anciently known) and phonolites of trachytic strata (Andes of Mexico).

The former are generally above the basalts; and the extraordinary development of felspar in that union, and the want of pyroxene, have always appeared to me very remarkable phenomena.

) The Cerro de Flores is a hill covered with tabulary blocks of greenish grey phonolite, enclosing long crystals (not fendillated) of vitreous felspar, altogether analogous to the phonolite of Mittelgebirge.

It is surrounded by pyroxenic amygdaloid; it would no doubt be seen below, issuing immediately from gneiss-granite, like the phonolite of Biliner Stein, in Bohemia, which contains fragments of gneiss embedded in its mass.

Does there exist in South America another group of rocks, which may be preferably designated by the name of volcanic rocks, and which are as distinct from the chain of the Andes, and advance as far towards the east as the group that bounds the steppes of Calabozo?

Of this I doubt, at least in that part of the continent situated north of the Amazon.

I have often directed attention to the absence of pyroxenic porphyry, trachyte, basalt and lavas (I range these formations according to their relative age) in the whole of America eastward of the Cordilleras.

The existence even of trachyte has not yet been verified in the Sierra Nevada de Merida which links the Andes and the littoral chain of Venezuela.

It would seem as if volcanic fire, after the formation of primitive rocks, could not pierce into eastern America.

Possibly the scarcity of argentiferous veins observed in those countries may be owing to the absence of more recent volcanic phenomena.

M.

Eschwege saw at Brazil some layers (veins?

) of diorite, but neither trachyte, basalt, dolerite, nor amygdaloid; and he was therefore much surprised to see, in the vicinity of Rio Janeiro, an insulated mass of phonolite, exactly similar to that of Bohemia, piercing through gneiss.

I am inclined to believe that America, on the east of the Andes, would have burning volcanoes if, near the shore of Venezuela, Guiana and Brazil, the series of primitive rocks were broken by trachytes, for these, by their fendillation and open crevices, seem to establish that permanent communication between the surface of the soil and the interior of the globe, which is the indispensable condition of the existence of a volcano.

If we direct our course from the coast of Paria by the gneiss-granite of the Silla of Caracas, the red sandstone of Barquisimeto and Tocuyo, the slaty mountains of the Sierra Nevada de Merida, and the eastern Cordillera of Cundinamarca to Popayan and Pasto, taking the direction of west-south-west, we find in the vicinity of those towns the first volcanic vents of the Andes still burning, those which are the most northerly of all South America; and it may be remarked that those craters are found where the Cordilleras begin to present trachytes, at a distance of eighteen or twenty-five leagues from the present coast of the Pacific Ocean.

* (* I believe the first hypotheses respecting the relation between the burning of volcanoes and the proximity of the sea are contained in Aetna Dialogus, a very eloquent though little-known work by Cardinal Bembo.

) Permanent communications, or at least communications frequently renewed, between the atmosphere and the interior of the globe, have been preserved only along that immense crevice on which the Cordilleras have been upheaved; but subterranean volcanic forces are not less active in eastern America, shaking the soil of the littoral Cordillera of Venezuela and of the Parime group.

In describing the phenomena which accompanied the great earthquake of Caracas,* on the 26th March, 1812, I mentioned the detonations heard at different periods in the mountains (altogether granitic) of the Orinoco.

(* I stated in another place the influence of that great catastrophe on the counter-revolution which the royalist party succeeded in bringing about at that time in Venezuela.

It is impossible to conceive anything more curious than the negociation opened on the 5th of April, by the republican government, established at Valencia in the valleys of Aragua, with Archbishop Prat (Don Narciso Coll y Prat), to engage him to publish a pastoral letter calculated to tranquilize the people respecting the wrath of the deity.

The Archbishop was permitted to say that this wrath was merited on account of the disorder of morals; but he was enjoined to declare positively that politics and systematic opinions on the new social order had nothing in common with it.

Archbishop Prat lost his liberty after this singular correspondence.

) The elastic forces which agitate the ground, the still-burning volcanoes, the hot sulphurous springs, sometimes containing fluoric acid, the presence of asphaltum and naphtha in primitive strata, all point to the interior of our planet, the high temperature of which is perceived even in mines of little depth, and which, from the times of Heraclitus of Ephesus, and Anaxagoras of Clazomenae, to the Plutonic theory of modern days, has been considered as the seat of all great disturbances of the globe.

The sketch I have just traced contains all the formations known in that part of Europe which has served as the type of positive geology.

It is the fruit of sixteen months' labour, often interrupted by other occupations.

Formations of quartzose porphyry, pyroxenic porphyry and trachyte, of grauwacke, muschelkalk and quadersandstein, which are frequent towards the west, have not yet been seen in Venezuela; but it may be also observed that in the system of secondary rocks of the old continent muschelkalk and quadersandstein are not always clearly developed, and are often, by the frequency of their marls, confounded with the lower layers of Jura limestone.

The muschelkalk is almost a lias with encrinites; and quadersandstein (for there are doubtless many above the lias or limestone with gryphites) seems to me to represent the arenaceous layers of the lower shelves of Jura limestone.

I have thought it right to give at some length this geologic description of South America, not only on account of the novel interest which the study of the formations in the equinoctial regions is calculated to excite, but also on account of the honourable efforts which have recently been made in Europe to verify and extend the working of the mines in the Cordilleras of Columbia, Mexico, Chile and Buenos Ayres.

Vast sums of money have been invested for the attainment of this useful end.

In proportion as public confidence has enlarged and consolidated those enterprises, from which both continents may derive solid advantage, it becomes the duty of persons who have acquired a local knowledge of these countries to publish information calculated to create a just appreciation of the relative wealth and position of the mines in different parts of Spanish America.

The success of a company for the working of mines, and that of works undertaken by the order of free governments, is far from depending solely on the improvement of the machines employed for draining off the water, and extracting the mineral, on the regular and economical distribution of the subterraneous works, or the improvements in preparation, amalgamation, and melting: success depends also on a thorough knowledge of the different superposed strata.

The practice of the science of mining is closely linked with the progress of geology;

and it would be easy to prove that many millions of piastres have been rashly expended in South America from complete ignorance of the nature of the formations, and the position of the rocks, in directing the preliminary researches.

At the present time it is not precious metals solely which should fix the attention of new mining companies; the multiplication of steam-engines renders it indispensable, wherever wood is not abundant or easy of transport, to seek at the same time to discover coal and lignites.

In this point of view the precise knowledge of the red sandstone, coal-sandstone, quadersandstein and molassus (tertiary formation of lignites), often covered with basalt and dolerite, is of great practical importance.

It is difficult for a European miner, recently arrived, to judge of a country presenting so novel an aspect, and when the same formations cover an immense extent.

I hope that the present work, as well as my Political Essay on New Spain, and my work on the Position of Rocks in the Two Hemispheres, will contribute to diminish those obstacles.

They may be said to contain the earliest geologic information respecting places whose subterraneous wealth attracts the attention of commercial nations; and they will assist in the classification of the more precise notions which later researches may add to my labours.

The republic of Colombia, in its present limits, furnishes a vast field for the enterprising spirit of the miner.

Gold, platinum, silver, mercury, copper, gem-salt, sulphur and alum may become objects of important workings.

The production of gold alone amounted, before the outbreak of the political dissensions, on the average, to 4700 kilogrammes (20,500 marks of Castile) per annum.

This is nearly half the quantity furnished by all Spanish America, a quantity which has an influence the more powerful on the variable proportions between the value of gold and silver, as the extraction of the former metal has diminished at Brazil, for forty years past, with surprising rapidity.

The quint (a tax which the government raises on gold-washings) which in the Capitania of Minas Geraes was, in 1756, 1761 and 1767, from 118, 102 and 85 arobas of gold (of 14 3/5 kilogrammes), has fallen, during 1800, 1813 and 1818, to 30, 20 and 9 arobas; an arob of gold having, at Rio Janeiro, the value of 15,000 cruzados.

According to these estimates the produce of gold in Brazil, making deductions for fraudulent exportation, was, in the middle of the eighteenth century, the years of the greatest prosperity of the gold-washings, 6600 kilogrammes, and in our days, from 1817 to 1820, 600 kilogrammes less.

In the province of San Paulo the extraction of gold has entirely ceased; in the province of Goyaz, it was 803 kilogrammes in 1793 and in 1819 scarcely 75. In the province of Mato Grosso it is almost nothing; and M. Eschwege is of opinion that the whole produce of gold in Brazil does not amount at present to more than 600,000 cruzados (scarcely 440 kilogrammes).

I dwell on these particulars because, in confounding the different periods of the riches and poverty of the gold-washings of Brazil, it is still affirmed in works treating of the commerce of the precious metals, that a quantity of gold equivalent to four millions of piastres (5800 kilogrammes of gold*) flows into Europe annually from Portuguese America.

(* This error is twofold: it is probable that Brazilian gold, paying the quint, has not, during the last forty years, risen to 5500 kilogrammes.

I heretofore shared this error in common with writers on political economy, in admitting that the quint in 1810 was still (instead of 26 arrobas or 379 kilogrammes) 51,200 Portuguese ounces, or 1433 kilogrammes; which supposed a product of 7165 kilogrammes.

The very correct information afforded by two Portuguese manuscripts on the gold-washings of Minas Geraes, Minas Novas and Goyaz, in the Bullion Report for the House of Commons, 1810, acc.

page 29, goes as far only as 1794, when the quinto do ouro of Brazil was 53 arrobas, which indicates a produce of more than 3900 kilogrammes paying the quint.

In Mr. Tooke's important work, On High and Low Prices part 2 page 2) this produce is still estimated (mean year 1810 to 1821) at 1,736,000 piastres; while, according to official documents in my possession, the average of the quint of those ten years amounted only to 15 arrobas, or a product quint of 1095 kilogrammes, or 755,000 piastres.

Mr. John Allen reminded the Committee of the Bullion Report, in his Critical Notes on the table of M.

Brongniart, that the decrease of the produce of the gold-washings of Brazil had been extremely rapid since 1794; and the notions given by M. Auguste de Saint Hilaire indicate the same desertion of the gold-mines of Brazil.

Those who were miners have become cultivators.

The value of an arroba of gold is 15,000 Brazilian cruzados (each cruzado being 50 sous).

According to M. Franzini the Portuguese onca is equal to 0. 028 of a kilogramme, and 8 oncas make 1 mark; 2 marks make 1 arratel, and 32 arratels 1 arroba.

) If, in commercial value, gold in grains prevails, in the republic of Columbia, over the value of other metals, the latter are not on that account less worthy to fix the attention of government and of individuals.

The argentiferous mines of Santa Anna, Manta, Santo Christo de las Laxas, Pamplona, Sapo and La Vega de Sapia afford great hope.

The facility of the communications between the coast of Columbia and that of Europe imparts the same interest to the copper-mines of Venezuela and New Grenada.

Metals are a merchandize purchased at the price of labour and an advance of capital; thus forming in the countries where they are produced a portion of commercial wealth; while their extraction gives an impetus to industry in the most barren and mountainous districts.

INDEX.

Acephali.

Action: electric, similarity of, in the electric eel and the voltaic battery.

volcanic, centre of.

connexion of.

Acosta, travels of.

Adansonia, or baobab of, Senegal.

Acuvajos, country of the.

Aerolites.

Africa: travels in.

deserts of.

Aguas Calientes: ravine of.

river of.

Agriculture: tropical.

early practice of.

influence of on individuals.

mean temperature required for the success of.

geology applied to.

in the island of Cuba.

zone of, in Spanish America.

Aguatire, the.

Ajuntas.

Alcaldes, or Indian magistrates.

Alegranza, island of.

Algodonal: crocodiles of.

Aloe, see Maguey.

Alligators.

Almond-trees.

Alphabet, application of the, in Indian languages.

Alta Vista: plain of.

natural ice-house of.

Gracia.

Alum: European.

mines.

Amalivaca.

Amasonia, arborea.

Amazon river: falls of the.

valley of the.

navigation of.

tributary streams of.

bridges over the.

course of the.

basin of the.

plains of the.

stones.

locality of.

Amazons, traditions of the.

Amygdaloide.

America: discovery of.

rapidity of vegetation in.

Savannahs of.

geological structure of.

early colonists of.

traditons of.

ancient name of.

supposed identity of, with Asia.

east of the Andes.

English.

population of.

Portuguese.

population of.

South.

plants of.

forests of.

missions of.

natives of.

waters of.

pampas of.

geography of.

geognostic description of.

configuration of.

mountains of.

extent of.

plains of Ibib, boundaries of.

America, Spanish: inhabitants of.

civil wars of.

state of society in.

productions of.

boundaries of.

frontier posts of.

population of.

extent of.

republics of.

commerce of.

agriculture of.

political position of.

Amerigo, Vespucci.

Andalusia, New: coasts of.

mountains of.

capital of.

inhabitants of.

earthquakes in.

extent of.

Andes: ascent of the.

branches of the.

structure of.

elevation of.

etymology of the name.

importance of the.

of Chili.

Angostura: commerce of.

geology of.

bark.

Anil, see Indigo.

Animals: effects of heat and cold upon.

organization of.

contemplations on the nature of.

hemispherical distribution of.

geography of.

domestic.

wild, herds of.

Animals, painted representations of, by native Indians.

Anthropophagy.

Antidotes, to poisons.

Antiles, the.

Antimano.

Ants: of the torrid zone.

use of by the natives as food.

Apes, different species of.

Apparatus, electrical.

Apples, American.

Apure river: voyage on the.

channel of.

navigation of.

junction of, with the Orinoco.

fetid waters of.

rise of the.

Apurito, island of.

Aquio, river.

Aradores.

Aragua: cotton plantations of.

boundaries of.

forests of.

plains of.

indigo grounds of.

cacao plantations of.

geology of.

vultures of.

Araguatos.

Araya: salt works of.

Peninsula of.

castle of.

pearls of.

inhabitants of.

scarcity of rain in.

geology of.

Archipelago: of St. Bernard.

of Chonos.

of Rosario.

Arenas.

Areverians, tribe of.

Areo, river.

Aroa: copper mines of.

river of.

Arowaks, tribe of the.

Arrua, the.

Artabrum, promontory of.

Arvi, the.

Asia, steppes of.