The Encyclopedia contains such particulars relative to that amazing chain of mountains as could be gathered from the accounts of the early writers, and especially from the more precise descriptions given by the Academicians who were sent to Peru in 1736, to measure the length of a degree of the meridian under the Equator. But, since that period, Geography has made rapid advances, and Mineralogy, emerging from its obscurity, has risen to the rank of a science. The vast American Continent has been explored in different directions, by adventurous and intelligent travellers. Of these by far the most conspicuous for enterprise, accuracy of observation, and extent of scientific research, is the celebrated Humboldt, whose various discoveries in the regions of the New World have deservedly excited so much interest. The narrative, however, of this accomplished traveller is not yet completed, and we must content ourselves at present with combining the incidental sketches which occur in his other publications. We trust that we shall be enabled to give a fuller and more precise account of the Andes in the article MOUNTAINS.

The Andes are distinguished above all the known mountain-chains, by their immense extent and their prodigious altitude. They run almost parallel to the west coast of the southern Continent of America, at a mean distance of between 100 and 200 miles, rising in some places to the enormous height of 20,000 feet; and stretch from the mouth of the river Atrato, on the isthmus of Darien, in the latitude of 8 degrees north, as far as Cape Pilares, at the outlet of the Straits of Magellan, in the 53rd degree of south latitude,—a range of at least 4200 miles. According to Humboldt, they send out, nearly at right angles to their colossal ridge, three dependent branches, called likewise Cordilleras by the Spaniards.

Of these secondary chains, the first and most northern is that of the coast of Venezuela, which is besides the highest and narrowest. With an irregular altitude, it bends eastwards from the Atrato, forming the Sierra of Abibó, the mountains of Cauca, and the high Savannahs of Folu, till it reaches the stream of Magdalena, in the province of St Martha. It contracts, as it approaches the Gulf of Mexico at Cape Vela; and thence extends to the mountain of Paria, or rather the Galley-Point in the island of Trinidad, where it terminates. This secondary chain attains its greatest known elevation where it rears the snowy summit, or Sierra Nevada, of St Martha and of Merida, the former being nearly 14,000, and the latter above 15,000 feet, in altitude. These insulated mountains, covered so near the equator with eternal snow, yet discharging boiling sulphureous water from their sides, are higher than the Peak of Teneriffe, and can be compared only with Mont-blanc. In their descent, they leave the Paramo or lofty desert of Rosa and of Mucachi; and on the west side of the lake Maracaibo, they form long and very narrow vales, running from south to north, and covered with forests. At Cape Vela, the mountain-chain divides into two parallel ridges, which form three confined valleys, ranging from east to west, and having all the appearance of being the beds of ancient lakes. These ridges, of which the northern is the continuation of the Sierra Nevada of St Martha, and the southern the extension of the snowy summits of Merida, are united again by two arms which seem to have been placed by the hand of nature, as dikes to confine the primeval collections of water. The three valleys thus enclosed are remarkable for their elevation above the sea, rising like steps one above another, the eastmost, or that of the Caraccas, being the highest. This plain was found by Humboldt to be elevated 2660 feet, while the basin of Aragua has only 1350 feet in height, and the Llanos, or reedy plains of Monai, spread within 500 or 600 feet above the level of the shore. The lake of the Caraccas appears to have forced a passage for itself through the quebrada, or cleft of Tipé, while that of Aragua has been gradually dissipated by a slow process of evaporation, leaving some vestiges of its former existence in pools charged with muriate of lime, and in the low islets called Aparecidas. The medium height of the Cordillera of the coast is about 4000 or 5000 feet; but its loftiest summit, next to the Sierra Nevada of Merida, is the Silla (or saddle) of the Caraccas, which was visited by Humboldt, and ascertained from barometrical measurement to have an elevation of 8420 feet. Farther to the eastward, the mountain-chain becomes suddenly depressed, especially its primitive rocks; the beds of gneiss and mica slate, meeting as they advance with accumulations of secondary calcareous substances, which envelope them completely, and rise to a great eleva- The incumbent mass of sandstone, with a calcareous base, extending from Capellnari, forms a detached range of mountains, in which no trace of primitive rock is found.

The second branch, which stretches from the Andes across the American Continent, and exhibits a chain of primitive mountains, is named by Humboldt the Cordillera of the cataracts of Orinoco. This very enterprising traveller surveyed it over an extent of upwards of 600 miles, from the Black River to the frontiers of the Great Bara; but the rest of the chain is very little known, running through unexplored wilds and regions almost inaccessible, occupied by fierce and independent tribes of savages. It leaves the great trunk between the 3d and 6th degree of southern latitude, and runs eastwards from the Paramo, or high desert of Tuquillo and St Martin, and the sources of the Guaviari, rearing the lofty summits of Umana and Caravani, and pouring forth the large rivers Meta, Zama, and Ymerida, which form the roudals, or tremendous rapids of Ature and Maypare, the only openings existing at present between the interior of the Continent and the plain of the Amazons. Beyond these cataracts, the chain of mountains again acquires greater elevation and breadth, occupying the vast tract enclosed between the rivers Caura, Cavyon, and Padamo, and stretching southwards to the boundless forests where the Portuguese settlers gather that potent drug, the sarpapilla. Farther eastwards this chain is not traced, no European or civilized Indian having ever explored the sources of the Orinoco; all access in that quarter being prevented by the ferocity of the Guaiacas, a dwarfish but very fair and warlike race, and by the valour of the Guajaribos, a most desperate tribe of cannibals. Beyond these recesses, however, we are made acquainted with the continuation of the chain of the cataracts, by the astonishing journey performed by Don Antonio Santos, who, disguised like a savage, his body naked, and his skin stained of a copper colour, and speaking fluently the several Indian dialects, penetrated from the mouth of the Rio Caronis to the Lake of Parime and the Amazons. The range of mountains sinks lower, and contracts its breadth to 200 miles, where it assumes the name of Serrania de Quineroa and Pacaraima. A few degrees farther eastwards, it spreads out again, and bends south to the Cano Pirara along the Mao, near whose banks appears the Cerro or hill of Ucucuano, consisting entirely of a very shining and yellow mica slate, which has therefore procured from the curiosity of early travellers the magnificent appellation of Dorado, or Golden Mountain. East from the river Esquibo, this Cordillera stretches to meet the granitic or gneiss mountains of Dutch and French Guyana, inhabited by confederated bands of Negroes and Caribs, but giving birth to the commercial streams of Berbice, Surinam, and Marony.

The chain of the cataracts of Orinoco, has only a mean height of about 4000 feet above the level of the sea. The greatest elevation occurs where the mountain of Duida rears its enormous mass from the midst of a luxuriant plain, clothed with the tropical productions of Palms and Ananas, and discharges from its steep sides, about the close of the rainy season, volumes of incessant flames. No one has yet had the resolution or perseverance to climb through the tangling and rampant bushes to its peak, which, measured trigonometrically, gives an altitude of 8465 feet above the sea. The whole mountain-group which forms this Cordillera, is distinguished by the abrupt descent of its south flank; nor is it less remarkable for containing no rock of secondary formation, or exhibiting any vestige of petrifications and organic remains. It contains only granite, gneiss, mica slate, and hornblende, without any casing or admixture of sandstone or calcareous matter.

The third great branch sent out from the trunk of the Andes, is that of the Chiquitos; which province it traverses, making a sort of semicircular sweep between the parallels of 15 and 20 degrees south latitude, and appearing to connect the colossal heights of Peru and Chili, with the mountains of Brazil and Paraguay. It supplies the rivers that feed the Maranon on the one side, and the Plata on the other. The structure and disposition, however, of the Cordillera of the Chiquitos still remain almost unknown.

These grand chains of mountains divide the southern Continent of America, from the latitude of 19 to that of 52 degrees, into three immense plains, which on the west side are shut up by the enormous ridge of the Andes, but are all open on the east, and towards the Atlantic Ocean. The most northern is the valley of the Orinoco, consisting of savannahs or level tracts covered with reedy herbage and scattered Palms. The next is the plain of the Maranon, which is entirely covered with dense impenetrable forests. The third and southmost valley is the Pampas; a dead flat of most prodigious expanse, clothed, like that of the Orinoco, with a coarse rank herbage, and abandoned to the occupation of countless herds of wild cattle.

Of these immense plains, the subsoil resembles the composition of the neighbouring mountains. In the valley of the Orinoco, the primitive rock is generally wrapt in a coat of sandstone with calcareous cement, or covered with calcareous concretions, which betray the vestiges of recent organic remains, but show none of the older impressions, such as the belemnites and ammonites so common in Europe. The woody plain of Maranon is distinguished by the thinness of its soil, and the total absence of any calcareous ingredients, the granite approaching close to the surface, which is in some places left quite bare over an extent of many furlongs. But the Pampas of Buenos Ayres are covered to a great depth with beds of alluvial deposits, in which the powers of vegetation, fomented by the rays of a burning sun, luxuriate in wanton profusion.

The disciple of Werner traces with delight, in the majestic features of the American Continent, the same order and succession of rocks which the sagacity of that illustrious Geologist had discovered in the mountains of Saxony. Granite appears still the oldest material of our globe: To it succeeds the laminated species, or gneiss; then mica slate containing garnets; next primitive slate, with beds of native alum; now slate mixed with hornblende; above this, greenstone, or primitive trap, followed by amygdaloid; and last of the series, porphyry slate. Resting or flanked against those primary rocks, beds of the older limestone begin to appear, followed by a suite of minerals, bearing indications of organic remains—mica slate, hornblende, gypsum, and calcareous sandstone. The only formations which Humboldt did not meet with in his extensive travels, were those of chalk, roestone, gray-wacke, topaz rock, and the compound of serpentine with granular limestone which occurs in Asia Minor. The grand ridge of the Andes is everywhere covered with porphyry, basalt, phonolite, and greenstone; which being often broken into columns, appear at a distance like ruined castles, and produce a very striking effect. Near the bottom of that enormous chain, two different sorts of limestone occur—one with a silicious base, enclosing sometimes cinnabar and coal—and another mostly calcareous, and cementing the secondary rocks. These formations are of enormous thickness and elevation. "Beds of coal are found in the neighbourhood of Santa Fé, 8650 feet above the level of the sea; and even at the height of 14,700 near Huancos in Peru. The plains of Bugota, although elevated 9000 feet, are covered with gypsum, sandstone, shell-limestone, and even in some parts with rock salt. Fossil shells, which, in the old Continent, have not been discovered higher than the summits of the Pyrenees, or 11,700 feet above the sea, were observed in Peru, near Micupampa, at the height of 12,800 feet; and again at that of 14,120, beside Huancavelica, where sandstone also appears. The basalt of Pichincha, near the city of Quito, has an elevation of 15,500 feet; while the top of the Schneekoppe in Silesia is only 4925 feet above the sea: the highest point in Germany where that species of rock occurs. On the other hand, granite, which in Europe crowns the loftiest mountains, is not found in the American Continent above the height of 11,500 feet. It is scarcely known at all in the provinces of Quito and Peru. The frozen summits of Chimborazo, Cayambé, and Antisana, consist entirely of porphyry, which, on the flanks of the Andes, forms a mass of 10,000 or 12,000 feet in depth. The sandstone near Cuenca, has a thickness of 5000 feet; and the stupendous mass of pure quartz, on the west of Caxamarca, measures perpendicularly 9600 feet. It is likewise a remarkable fact, that the porphyry of those mountains very frequently contains hornblende, but never quartz, and seldom mica."

"The central Andes are rich beyond conception in all the metals, lead only excepted. One of the most curious ones in the bowels of those mountains is the paco, a compound of clay, oxyd of iron, and the muriate of silver with native silver. The mines of Mexico and Peru, so long the objects of envy and admiration, far from being yet exhausted, promise, under a liberal and improved system, to become more productive than ever. But nature has blended with those hidden treasures the active elements of destruction. The whole chain of the Andes is subject to the most terrible earthquakes. From Cotopaxi to the South Sea, no fewer than forty volcanos are constantly burning; some of them, especially the lower ones, ejecting lava, and others discharging the muriate of ammonia, scorified basalt, and porphyry, enormous quantities of water, and especially moya, or clay mixed with sulphur and carbonaceous matter. Eternal snow invests their sides, and forms a barrier to the animal and vegetable kingdoms. Near that confine, the torpor of vegetation is marked by dreary wastes." (Edin. Review, Vol. XV. p. 233.)

We may subjoin, that, near Quito, the liquid mud ejected by the volcanos often involves myriads of small dead fish. In some parts, the mountains, like the fabled cave of Eothis, seem at times to let out their imprisoned air, and produce such furious gusts of wind as to sweep everything before them to a vast distance. In other districts, the efforts of the contending elements are betrayed, especially during the rainy season, by a doleful moaning noise, or hollow and portentous groans, enough to cast a darker shade on the gloom of superstition, and to fill the imagination of the remotest settler with secret awe and dread.

A person who, for the first time, climbs the mountains of Switzerland, is astonished to witness, in the space perhaps of a few hours, so rapid a change of climate, and such a wide range of vegetable productions. He may begin his ascent from the midst of warm vineyards, and pass through a succession of Chestnuts, Oaks, and Beeches, till he gains the elevation of the hardy Pines and stunted Birches, or treeds on Alpine pastures, extending to the border of perpetual snow. But within the tropics everything is formed on a grander scale. The boundary of permanent congelation is 7500 feet higher at the equator than at the mean latitude of 45 degrees. Under a burning sun, Ananas and Plantains grow profusely near the shore; Oranges and Limes occur a little higher; then succeed fields of maize and luxuriant wheat; and the traveler has actually reached the high plain of Mexico, or the still loftier vale of Quito, before he finds a climate analogous to that of Bordeaux or of Geneva. Now only commences the series of plants which inhabit the central parts of Europe.

But the very magnitude of the Andes appears to have the effect of diminishing the impressions of awe and wonder, which the sight of them so powerfully excites. The country on which they rest, is heaved to such a vast altitude above the sea, that the relative elevation of their summits becomes diminished in comparison with that of the surrounding amphitheatre. The majestic forms of Chimborazo, Cotopaxi, and Antisana, though 6000 feet higher than Montblanc, and clothed, like it, with eternal snow, seem to a traveller scarcely more sublime from the plains of Riobamba and Quito, than this celebrated mountain when viewed from the vale of Chamouni. It requires some time for his imagination to expand itself to the new scale of grandeur.

The central Andes, with all their magnificence, want a feature which, in the higher latitudes, contributes so much to the beauty and sublimity of the Alpine scenery. They have no vestige whatever of Glaciers, those icy belts dropping from the limits of congelation, and spreading in concrete sheets, or hanging in disjointed columns fantastically thrown, which occur alike in the heart of Switzerland and on the northern shores of Norway and Lapland. This defect is evidently owing to the almost uniform temperature which prevails near the equator. In those torrid regions, the days are constantly of the same length, and the sun shines through the whole year with very nearly equal force. The limit of perpetual congelation is hence marked on the sides of the mountains of Quito with singular precision. The temperature decreases regularly in proportion as one ascends them, till at a certain altitude it comes to the point of freezing, where the permanent field of snow begins to appear, defined with an almost unvarying border. But in the higher latitudes, the sun remains, during the summer, so long above the horizon, and shines with such augmented force, that the heat of the atmosphere, and consequently of the surface of the ground, suffers a wide alteration in the different seasons. To the general investure of snow, is therefore annexed every winter, a zone of considerable breadth, which again softens and partly melts away during the continuance of the summer months. This alternate thawing and freezing, occasions the production of glaciers, by converting successively the lower detached masses of snow in the precipitous flanks of the mountains, into a collection of broken and intermingled pillars of translucent ice.

For the same reason the Andes, though torn by flaming volcanos, and convulsed by frequent and terrible earthquakes, are exempt from those avalanches and boulders which, in Switzerland and other mountainous parts of Europe, often bury the helpless traveller in a torrent of snow, and batter down whole villages by the sudden discharge of a shower of rocks. Under the equator, the variation of temperature throughout the year is so small, as not to disturb the solidity of the vast collections of snow. But on the flanks of the Alps or Pyrenees, as the heat of the summer increases, portions of the upper field of snow become loosened, and, sliding down, put other masses likewise in motion, till spreading wider, and gaining accelerated force, the whole tide precipitates itself to the plain, sweeping all before it. Such is the accident of an avalanche; but the occurrence of an embolism, though less frequent, is more tremendous. When the alternation of frost and thaw detaches a mass of rock, it rolls down the side of the mountain with irresistible fury, shivering into fragments and tearing everything opposed to it, overwhelming men, cattle, and houses, in one common heap of ruins.

But the Andes are distinguished from the chains of the European mountains, by frightful quebradas or perpendicular rents, which form very narrow vales of immense depth, whose terrific walls, fringed below with luxuriant trees and shrubs, seem to lift their naked and barren heads to the distant skies. The noted crevices of Chota and Cutaco are nearly a mile deep, the former measuring 4950, and the latter 4300 feet, in a vertical descent. The task of crossing such tremendous gullies, is often a work of infinite toil and extreme danger. In those mountainous countries, travellers are accustomed to perform their journeys sitting in chairs fastened to the backs of men, called cargueros or carriers. These porters are Mulattos, and sometimes Whites, of great bodily strength and action, who will climb along the face of precipices, bearing loads of twelve and fourteen, or even eighteen stone. These cargueros lead a vagabond life, exposed to incredible fatigue, but recommended to them by its irregular course. Often those wretched men toil over mountains for the space of eight or nine hours every day, till, like beasts of burthen, they have their backs chafed, and made quite raw with the load. In this deplorable condition, they are not unfrequently abandoned by unfeeling travellers, and left alone to sicken, pine, or die in the forests. Yet their earnings would appear inadequate to such violent and overpowering exertions, since they receive scarcely three guineas for performing the journey from Ibague to Carthagena, which requires fifteen, and perhaps twenty-five or thirty days.

The Icononzo, remarkable for its natural bridges, is a small quebrada or cleft of the mountains, through which flows the river of the Summa Paz, descending from the highest upland desert. The rocks consist of two different kinds of sandstone, the one extremely compact, and the other of a slaty texture, divided into their horizontal strata. The rent was probably caused by an earthquake, which the harder portion of the stony mass had resisted, and now connects the upper part of the chasm. This natural arch is 50 feet long, 40 broad, and 8 feet thick at the middle. Its height is about 300 feet above the surface of the torrent, which has a medium depth of twenty feet. About 60 feet below the natural bridge, another smaller arch occurs, composed of three slanting blocks of stone wedged together, which had probably fallen from the roof at the same instant of time, and struck against the sides of the crevice in their descent.

The natural bridge of Icononzo has perhaps no counter-part in the old world; but the writer of this article had the pleasure of seeing, in early life, a similar phenomenon, scarcely inferior to it, in the United States of America. We allude to the famous arch, described by Mr. Jefferson, which crosses the Cedar Creek in Rockbridge county, about an hundred miles beyond the Blue Ridge, in the higher district of Virginia. The divided rock is a pure limestone, leaving a chasm about 90 feet wide, of which the walls are 250 feet high, sprinkled with verdant bushes, and enamelled with gay flowers, among which the aquilegia is conspicuous. This bridge, viewed from a little distance below, has all the appearance of a Gothic arch; and is of such solidity, that loaded waggons used formerly to pass along it, till a more convenient line of road was formed.

In some places, the natives of Peru connect the clefts of their mountains by pendulous bridges thrown fearlessly across, and suspended from both sides of a gap. They are formed of ropes made of the tough fibres of the agave, hanging in a gentle parallel curve, and covered with reeds or canes, with occasionally a narrow border of basket-work. The intrepid Indian, regardless of the horrors of the untamed abyss which yawns from below, commits himself to his frail and floating arch, and swiftly glides along its bending curvature, till he gains the opposite bank.

The Andes likewise give rise to waterfalls of immense height and amazing force. The cataract of Tequendama, considered in all its circumstances, exceeds any other in the known world. The basin which feeds its streams is the vast plain of Bogota, 7465 feet above the level of the sea, encircled completely with lofty mountains, except where the water, aided probably by the concussion of an earthquake, has cut for itself a narrow passage. The river Fumcha, swelled by numerous feeders, gradually contracts its channel to the breadth of about 40 feet, and then gathering augmented force, dashes at two bounds from a perpendicular height of near 600 feet, into a dark gulf. Owing to the excessive rapidity and depth of its current, it must discharge a prodigious volume of water, which quite stuns the ear by the roar of its crash; while it raises enormous clouds of thick spray and vapour, that continually bedew, and perhaps quicken the vegetation of the adjacent grounds. Everything conspires to exalt the beauty and grandeur of the scenery. "Independent of the height and mass of the column of water," says Humboldt, "the figure of the landscape, and the aspect of the rocks, it is the luxuriant form of the trees and herbaceous plants, their distribution into thickets, the contrast of those craggy precipices, and the freshness of vegetation, which stamp a peculiar character on these great scenes of nature." The transition from a temperate to a warm climate is rapid and surprising. The plain of Bogota bears rich crops of wheat, then succeed Oaks and Elms, intermingled with Aralias, Bogonias, and the Yellow-bark trees; but, immediately below the cataract, a few Palms appear, as if it were to mark the advance to a sultry soil.

A lively idea of the character and grand features of the Andes may be conceived from the account which the celebrated Humboldt has given of his journey across that majestic chain. Our readers will be glad to peruse it in the author's own words:

"The mountain of Quindiu, in the latitude of 4° 36', is considered as the most difficult passage in the Cordilleras of the Andes. It is a thick uninhabited forest, which, in the finest season, cannot be traversed in less than ten or twelve days. Not even a hut is to be seen, nor can any means of subsistence be found. Travellers, at all times of the year, furnish themselves with a month's provision, since it often happens, that, by the melting of the snows, and the sudden swell of the torrents, they find themselves so circumstanced, that they can descend neither on the side of Carthago, nor that of Ibague. The highest point of the road, the Garito del Paramo, is 11,500 feet above the level of the sea. As the foot of the mountain, towards the banks of the Cauca, is only 3150 feet, the climate there is generally mild and temperate. The pathway, which forms the passage of the Cordilleras, is only 12 or 15 inches in breadth, and has the appearance, in several places, of a gallery dug, and left open to the sky. In this part of the Andes, as almost in every other, the rock is covered with a thick stratum of clay. The streamlets which flow down the mountains have hollowed out gullies about 20 feet deep. Along these crevices, which are full of mud, the traveller is forced to grope his passage; the darkness of which is increased by the thick vegetation that covers the opening above. The oxen, which are the beasts of burden commonly used in this country, can scarcely force their way through these galleries, some of which are more than a mile in length; and if, perchance, the traveller meets them in one of these passages, he finds no means of avoiding them, but by turning back, and climbing the earthen wall which borders the crevice, and keeping himself suspended, by laying hold of the roots which penetrate to this depth from the surface of the ground."

"We traversed the mountain of Quindiu in the month of October 1801, on foot, followed by twelve oxen, which carried our collections and instruments, amidst a deluge of rain, to which we were exposed during the last three or four days, in our descent on the western side of the Cordilleras. The road passes through a country full of bogs, and covered with Bamboos. Our shoes were so torn by the prickles which shoot out from the roots of these gigantic graminia, that we were forced, like all other travellers who dislike being carried on men's backs, to go barefooted. This circumstance, the continual humidity, the length of the passage, the muscular force required to tread in a thick and muddy clay, the necessity of fording deep torrents of icy water, render this journey extremely fatiguing; but however painful, it is accompanied by none of those dangers with which the credulity of the people alarm travellers. The road is narrow, but the places where it skirts the precipices are very rare."

"When travellers reach Ibague, and prepare to cross the forests of Quindiu, they pluck in the neighbouring mountains, several hundred leaves of the Vijao, a plant of the family of the Bananans, which forms a genus approaching to the Thalia, and which must not be confounded with the Heliconia Bibei. These leaves, which are membranous and silky, like those of the Musa, are of an oval form, two feet long and 16 inches broad. Their lower surface is a silvery white, and covered with a farinaceous substance which falls off in scales. This peculiar varnish enables them to resist the rain during a long time. In gathering these leaves, an incision is made in the middle rib, which is the continuation of the foot-stalk; and this serves as a hook to suspend them, when the moveable roof is formed. On taking it down, they are spread out, and carefully rolled up in a cylindrical bundle. It requires about a hundred weight of leaves to cover a hut large enough to hold six or eight persons. When the travellers reach a spot in the midst of the forests where the ground is dry, and where they propose to pass the night, the cargueros lop a few branches from the trees, with which they make a tent. In a few minutes, this slight timber work is divided into squares, by the stalks of some climbing plant, or the threads of the agave placed in parallel lines, 12 or 13 inches from each other. The Vijao leaves meanwhile have been unrolled, and are now spread over the above work, so as to cover it like the tiles of a house. These huts, thus hastily built, are cool and commodious. If, during the night, the traveller feels the rain, he points out the spot where it enters, and a leaf is sufficient to obviate the inconvenience. We passed several days in the valley of Boquila, under one of those leafy tents, which was perfectly dry, amidst violent and incessant rains." For farther information relative to the structure of the Andes, see the various sketches given by Humboldt, and particularly an abstract of his Geological Observations inserted in the Journal de Physique, Vol. LIII. for 1801.