takes of the character of the Patagonian Pampas. The south shores of Hoste and Navarin islands, which also belong to the Tierra del Fuego group, are hornblende, which is also the chief component part of Cape Horn. Clarence Island is of a more rugged form than King Charles's Land, and tolerably verdant; in the Barbara channel, which separates it from Desolation Island, the fragments of rocks which compose the small islands are thickly strewed, and form the transition to the rough granitic mountains of the western part of Magalhaen's strait. The highest mountains, as we have observed, are in the slate formation, on the western side of King Charles's South Land. (See the articles STRAITS of MAGALHAENS and TIERRA DEL FUEGO; and Captain King's Charts.) Volcanos are said to exist in the Andes of Patagonia; and of these there are mentioned San Clemente in lat. 46°, Medialara in lat. 44° 30', and Minchimavidar in lat. 43°. The most remarkable feature in the physical constitution of the Andes of Chili is the great extent of volcanic action that has existed in past ages and is still in operation. No less than nineteen points of eruption, situated in a continuous line from south to north, that is, in the direction of the range, which have heaped up their ejected matter so as to form lofty mountains, have received distinct names, and there are probably many more of no inconsiderable importance which are still unknown. The most remarkable of the volcanoes of Chili are Villarica in lat 39° 8', Maypu in lat. 34° 10', and Peteroa in lat. 35° 15'. Villarica is always in a state of activity, and may be seen, it is said, at a distance of 150 miles. Our more detailed geological description is, from want of materials, confined to the Andes of Peru and Colombia, and especially the latter.

sandstone, or newer beds of the grauwacke series, and to the lower beds of the new red sandstone, the rothe todte liegende of the Germans. A red sandstone covers an extent of country 25 leagues in length, forming the whole table-land of Tarqui and Cuença in the Andes of Quito, at an elevation of from 8300 to 9600 feet, and it rises in the Paramo de Saar to the height of 12,150 feet, the thickness of the whole mass exceeding 5100 feet. The formation of red sandstone in the province of Quito is generally very argillaceous, some times slaty, and alternates with a conglomerate containing fragments of porphyry, and Humboldt found in it trunks of monocotyledonous trees four feet long and fourteen inches in diameter. It also contains there beds of an opaque limestone, and of a saccharoid limestone, like the marble of Carrara. In the llanos (plains) of Venezuela, these immense steppes, or mountain-plains, uniform like the surface of the sea over an area of 10,000 leagues, which stretch from the Sierra Nevada de Merida to the mouths of the Orinoco, are composed of a series of secondary rocks, the lowest of which is a red sandstone, or conglomerate of rounded fragments of quartz and flinty slate united by an argillaceous cement, sometimes of as vivid a red as cinnabar. This sandstone appears at the surface over the greater part of the llanos, but towards the east it is covered by beds of limestone and gypsum. In New Granada, the slaty fine-grained sandstone occurs to a greater extent than the coarse conglomerate. The latter disappears almost entirely when the formation rises to 5000 feet above the level of the sea; the sandstone of the table-land of Santa Fe de Bogota, at an elevation of 10,780 feet, is composed of small quartzose grains, sometimes so closely united as to give the rock the appearance of a granular quartz; it nowhere displays variegated colours, and animal remains are extremely rare in it. A similar red sandstone occurs in the great table-land of Caxamarca in Peru, at the height of 9350 feet. In the red sandstone of Santa Fe de Bogota, beds of coal are found, and in the great tract of red sandstone, between the lower part of the MICA-SLATE is, next to porphyry, the rock of most fre- river Magdalena and Santa Fe, coal occurs in several places. quent occurrence in the Andes, and more especially north Coal is also found at Huanuco in Peru, at an elevation of of the equator. In the Nevada de Quindiu of New Granada, 14,750 feet, the greatest elevation probably at which coal it attains a thickness of more than 3800 feet; it contains, in has yet been discovered. It occurs there in a compact limesome places, beds of granular limestone, occasionally re- stone, but whether that is a subordinate formation in the sembling the finest Carrara marble; but limestone, subor- red sandstone does not appear. Humboldt observed, between dinate to gneiss and mica-slate, is a much more rare occur- the seventh and eighth degrees of south latitude, a great rence than in the Alps and Pyrenees. Not far from formation, which he has called a secondary quartz rock, as Popayan, it contains beds of quartz and beds of gypsum, it seems to replace the red sandstone on the western declisulphur being found in the quartz, and in one place Hum-vity of the Andes, and is covered immediately by magnesian boldt observed a bed of lamellar graphite. It often passes limestone. It is a granular and compact quartz, stratified, by insensible gradations into clay-slate. without organic remains, and attains a thickness of several thousand feet.

The Stratified Rocks.

GNEISS is found at intervals throughout the greater part of the range, often associated with granite, and often passing into mica-slate. It frequently contains large quantities of garnet.

CLAY-SLATE Occupies a space of small extent in the Andes. North of the equator, it is found immediately under secondary formations in the table-land of Santa Fe de Bogota, and south of the equator it serves as a basis to the porphyry in the Andes of Quito. It is found immediately beneath a secondary limestone at the height of 12,800 feet in the ridge of the Andes of Peru, and rests on granite on the western declivity of the same part of the range: but Humboldt is of opinion that the chief mass of the slate-rocks of South America belongs to the transition series of the Wernerian school, rather than to primary strata.

QUARTZ ROCK. South of Chimborazo, near Hecatacumba, in the Andes of Quito, there occur enormous masses of quartz rock mixed with mica. The primitive quartz observed in the mountains of Europe cannot be compared in thickness nor extent to that of South America: on the western declivity of the Andes of Peru, it attains the enormous thickness of 6000 feet, and there and elsewhere it covers many leagues. It contains gold, mercury, and specular iron in many places, and in the celebrated sulphur mountain of Tiscan, in latitude 2° 13' S., the sulphur is contained in a bed of quartz 1300 feet thick, subordinate to mica-slate, at an elevation of 8000 feet. Gold and sulphur are also found in a quartz rock in the Andes of Peru near Caxamarca, and the celebrated quicksilver mines of Guancavelica in Peru are also in the same rock.

RED SANDSTONE. A red sandstone occurs to a vast extent in the Andes of Peru, and over a great part of Colombia, not only in the Andes, but in the country east of that range, and to the shores of the Atlantic. It is often a coarse conglomerate, and passes through all gradations of structure to that of a fine-grained sandstone. From Humboldt's description of its occurrence at different places, it appears to belong to different ages, to the old red

No. 66.-SUPPLEMENT.

The red sandstone of New Granada is covered by lamellar gypsum and by fetid limestone. In the basin of the Cauca and the plateau of Santa Fe, the former being 5750 feet lower than the other, the three formations of sandstone with coal, gypsum, and compact limestone succeed each other very regularly, and at Zipaquira, in the table-land of Santa Fe, rock-salt associated with this same gypsum and limestone has been worked for ages. The saliferous deposit is not less than 830 feet thick, and is covered by great masses of granular gypsum, the red sandstone appearing beneath the saliferous clay. Deposits of rock-salt and brine-springs are of frequent occurrence in traversing the eastern cordillera of New Granada from S.W. to N.E. for a distance of more than 50 leagues. Rock-salt is also found in the Peruvian provinces of Chachapoyas, on the eastern declivity of the Andes, and, what is remarkable, contains there masses of galena or sulphuret. of lead. At Huara, on the coast of Peru, between Lima and Santa, rock-salt is worked like marble in a quarry, and at the same place rocks of porphyry pierce through beds of the purest rock-salt. The red sandstone of the llanos of Venezuela is covered by a whitishgrey compact limestone, and above the limestone there occurs gypsum alternating with beds of marl. This limestone, according to Humboldt, is an equivalent of the zechstein of the Germans, the magnesian limestone of English geologists. It is met with in various parts of the Andes of Peru, at elevations from 9000 to 14,000 feet, and it contain beds of bituminous marl slate, with impressions of fish, (as at Mansfeld, in Germany,) near Pasco, in the Andes of Peru, at the height of 12,800 feet. In the mine Santa Barbara, near Guancavelica, an immense bed of sandstone, containing a deposit of mercury, is met with in this same limestone. It does not appear, from the observations of Humboldt,

that any of the secondary strata later than the magnesian | kinds of porphyries, or even their chief localities, would be limestone occur in any part of the Andes, or the adjoining both tedious and unprofitable; it is enough to say, that they country, which was visited by him, and he expressly says occur throughout the whole range of the Andes, at all elethat he never met with either oolite or chalk. The only vations, and that the highest summits are frequently comtertiary formation he speaks of is one in the table-land of posed of them. Santa Fe de Bogota, which appears to have been a lacustrine deposit, and in which he found enormous bones of the extinct species called the mastodon. That the whole series of the secondary strata above the magnesian limestone should be wanting, and that there should be a total absence of all tertiary marine beds in one-half of the continent of South America is very extraordinary, and scarcely probable. But notwithstanding this imperfect state of our knowledge respecting that vast country, an eminent French geologist, M. Elie de Beaumont, in his eagerness to generalize a favourite theory, a theory intended to show a connexion between the elevation of mountain-chains and the extinction of species of organic remains in the successive sedimentary deposits, has, of late, not hesitated to declare his belief, that the whole line of the Andes must have been upheaved by a single and instantaneous convulsion; that that convulsion was the last which has taken place in the solid covering of the earth, and that, by the agitation which it produced in the ocean, it was the immediate cause of the general deluge. So great a departure from the rules by which philosophical inquiries ought to be guided is a remarkable proof how dangerous, in a progressive science, an attachment to a particular theory may prove,-how very readily arguments with a mere semblance of plausibility will be admitted, even by a man who has worked assiduously in the field of observation, and knows full well how extensive and accurate our observations must be, before any general conclusions can safely be deduced from them.

The Unstratified Rocks.

The most elevated summits of the Andes-the composition of which is known-are either volcanic, or are composed of porphyry. Granite, which, in the old continent, rises to elevations of 15,000 feet, is never found at great heights in the Andes, and, indeed, forms but a small part of their external surface. Humboldt says, that one might pass years in travelling through the Andes of Quito and Peru, almost without seeing it, and he never met with it at a greater elevation than 11,500 feet. It is seen at the foot of the range in the plains of the Orinoco and Amazon, and on the shore of the Pacific between Lima and Truxillo. But Humboldt distinguishes three different kinds of granite, one which he calls primitive, and considers as the foundation upon which all other rocks were deposited, in accordance with the Wernerian hypothesis; another, which he makes of posterior formation to gneiss, but anterior to mica-slate; and a third, older than clay-slate, but of a formation subsequent to that of mica-slate. Modern discoveries have shown that granites, undistinguishable from one another in their mineralogical characters, are associated with some of the most modern of the secondary strata; and these distinctions of Humboldt are founded upon erroneous theoretical views, because the granite that lies under the gneiss may have been protruded to the surface later than that which is associated with the mica-slate. The same observations apply to his old and new syenites,--a variety of granite containing a mixture of hornblende, which is found in several parts of the Andes of Peru and Colombia. Porphyry is, by far, the most widely-extended of all the unstratified rocks of the Andes, and Humboldt distinguishes two kinds,-one which, he says, reposes immediately upon primitive rocks, and is not metalliferous; and another, which is often rich in metals and appears to belong to the transition period. The primitive porphyry is of rare occurrence; it is found on the western declivity of the Andes of Peru, at an elevation of about 3800 feet, and rests immediately upon granite. In the Andes of Peru, Quito, and New Granada, among an innumerable variety of porphyritic rocks, the masses of which are from 16,000 to 19,000 feet in thickness, there is not one which Humboldt considers as belonging to the primitive porphyries. They often exhibit superb columns, as at Pisoje, at the western declivity of the volcano of Purace, where there is a magnificent colonnade, the pillars of which are eighteen feet long, and formed of regular prisms of five, six, and seven sides. They have also very often a globular structure, as if the mass were composed of an aggregation of balls, which separate by decomposition into concentric layers. This globular structure is extremely common in the unstratified rocks of the Andes. To describe the various

Next in importance to porphyry among the rocks of igneous origin is that called TRACHYTE, (from paxús, trachus,) rough, because it has a harsh, rough feel. There are many varieties of it, but its most characteristic form is a hard rock with a granular basis of glassy felspar, and including separate crystals of glassy felspar usually with a mixture of hornblende, and often mica; and these materials are united in so many different proportions as to produce rocks of very different aspects. Trachytes occur throughout the whole range of the Andes of Chili, Peru, and Colombia; the porphyries are often covered by them, and it is not easy to define the limits between trachytes which pass into porphyry and those which are produced by active volcanos. Like porphyry and basalt, trachyte is often found in columns of great regularity, as in Chimborazo, where it is met with in slender prisms of 50 feet long. It occurs in enormous masses, for Humboldt says that in Chimborazo and Pichincha it undoubtedly attains a thickness of from 14,000 to 18,000 feet, and in continuous masses. The trachytes are most frequently not covered by any other formations except recent volcanic products, and this is also, in general, the case with the porphyries; but these are sometimes covered by the older sedimentary deposits, showing that there are porphyries of very different ages in the Andes; and there is every reason to suppose that trachytes have also been formed at various periods.

The Andes are often throughout a great extent wholly destitute of the trap-rocks: neither in Chimborazo, Antisana, nor Pichincha are there any rocks of this class; but basalt characterised by olivine, and regularly columnar, is found in the table-land of Quito, near Popayan, and on the western banks of the Cauca. The basalt, or trap-formation, in the vicinity of Popayan, as well as in other situations in the Andes, is accompanied by clay of great thickness, which renders the passage of the cordilleras from Popayan to Quito extremely difficult during the rainy season.

Volcanos.

No part of the world has been subjected to greater revolutions from volcanic fires than the range of the Andes. The igneous action has been confined to this western side of the continent, for, east of the Andes, throughout the whole country from the base of the mountain-range to the Atlantic, a space of more than 500,000 square leagues, neither porphyry, basalt, trachyte, nor any active volcanos have yet been discovered, either in the plains, or in the mountains of Guiana and Brazil. In the range of the Andes, where their products do not cover the whole surface, they are found in insulated masses on the ridges and on the sides of the mountains rising in the form of pyramids, or of cones, amidst the stratified rocks of different ages. All the volcanos, whether extinct or active, have burst forth amidst porphyries, basalts, and trachytes; all the loftiest summits of the range are composed of trachyte, and the opening is usually in the latter rock. It may be considered as a general rule, that when the mountains rise much above the limit of perpetual snow, that is, from 14,700 to 15,800 feet in the equatorial regions, the rocks commonly called primitive, such as granite, gneiss, and mica-slate, disappear, and are replaced by porphyries and trachytes. That these last substances are often granite, gneiss, and slates, altered by the action of heat, is rendered probable by many circumstances connected with them, and the trachytes of the Andes frequently include fragments of those primary rocks. It is very difficult to draw the line of separation between the various kinds of unstratified rocks, all of which are now admitted by most geologists to be of igneous origin, Granites and porphyries change into traps and trachytes: these last into the lavas of active volcanos; and thus any conclusions as to the ages of the unstratified rocks, drawn from mere mineralogical differences, are open to many sources of error, The glassy lava, called obsidian, is often met with in the Andes, and exhibits many shades of colour, from deep black to a clear, colourless glass. Beds of it, 16 inches thick, occur in the trachyte of Quinché, in the table-land of Quito. Fragments of rock, including nodules or lumps of obsidian are thrown out by Cotopaxi, and obsidian in the form of balls, and in those elongated pear-shaped forms called tears, is ejected by the volcano of Sotara near

で

AND

tiful of all the colossal summits of the Andes.
perfect cone, which, covered with an enormous bed of snow,
The form of Cotopaxi is the most regular and beau-
shines with a dazzling lustre at sunset, against the azure
vault of heaven. The crater is surrounded with a wall of
scoriæ, but it was only seen by Humboldt by means of a
It is a
telescope, for the cone being surrounded with deep rents and
fissures, cannot be approached.

subject to repeated earthquakes, and accordingly, no part of
the world has suffered more from their dreadful effects.
A region so underlaid by volcanic fires could not fail to be
Sometimes the shocks come without giving any warning
at all, and ruin and devastation are spread over a dis-
trict which, an instant before, had been in a state of
peaceful repose; in general, however, the inhabitants are
forewarned of the approach of the convulsion, but the
interval between the announcement and the arrival of
the destroying force is too short to admit of any pre-
cautions against the loss of property; it is well if there be
time enough to escape from death.
of the occurrence, that the inhabitants construct their
dwellings so as to diminish the risk of damage to the
building, and to facilitate their own escape. But no pre-
Such is the frequency
cautions can give confidence in such a case, and the terror
which takes possession of the people extends to the brute
creation, for the animals howl piteously when they feel the
ground rocking under them. The effects are often produced
far from the supposed centre of the volcanic action, for even
the towns on the sea-shore are often destroyed. The whole
of Chili is particularly subject to earthquakes. The city of
Copiapo was entirely destroyed in the year 1819, not a house
being left standing; and the city of Conception has been
twice destroyed, viz., in 1730 and 1751. An earthquake of
tremendous force occurred on the 19th of November, 1822,
which shook not only the whole of the low country of Chili,
but was felt in the mountains, and even at Mendoza and
San Luis, on the eastern side of the chain. The towns of
Valparaiso, Mellipilla, Quillota, and Casa Blanca, were
almost destroyed, and the capital, Santiago, was considerably
damaged. It was felt on the same day at Lima, in latitude
120, and at Conception, in latitude 37°, a distance of more
than 1700 miles. One of the most remarkable effects of
this earthquake was the elevation of the land on the coast;
above a hundred miles of it was permanently upraised to
the height of three or four feet, a portion of the bed of the
sea being converted into dry land, covered with oysters,
mussels, and other shell-fish. A circumstantial account of
the phænomena which occurred near Valparaiso, by Mrs.
Graham, who was then living in the country, will be found
in her Journal of a Residence in Chili, and in the first vo-
lume of the Second Series of the Transactions of the Geolo-
gical Society. The volcano of Maypu, situated about 170
miles E.S.E. of Valparaiso, which had been dormant for
several years, has had frequent eruptions since the great
earthquakes of 1822, for it was not one shock only which
took place; many succeeded at very short intervals, even to
the end of the following September.

Popayan, to the distance of several leagues, and scattered | heat. 523 about like fragments of flint on the chalk-downs. Pumicestone, which is nothing more than obsidian frothed up by the admission of air or watery vapour to it when it was in a fluid-state, is found to a great extent in many of the volcanos of the Andes; there are immense subterranean quarries of it at the foot of Cotopaxi, and for more than 40 leagues westward of the volcano, the ground is covered with fragments of pumice and cinders of trachytes. Volcanic-tuff, which is a stone more or less compact, made up of fragments of hard lava, cinders, and ashes, agglutinated together, covers immense tracks on the flanks of the Andes and on the table-lands. It is often very friable, and in many places contains blocks of pumice, which are sometimes from 25 to 30 feet long. In a region where almost all the burning volcanos rise above the limit of perpetual snow, deluges of water are often produced by the melting of the snow, and by the bursting of cavities in which water had accumulated by infiltration, and these carry along with them the loose stones, and give rise in lower regions to depositions of this tuff, of a magnitude in proportion to the volume of water and the loose materials it meets with in its descent. A liquid mud sometimes issues from the sides of the volcanos of the Andes, as when, in 1698, the peak of Carguairazo sunk down, and more than four square leagues were covered with mud; and, what is very remarkable, small fish which inhabit the streams of the province of Quito were seen in thousands, enveloped in the muddy eruption. These fish live in subterraneous lakes; at the time of great eruptions the sides of these lakes are burst, the fish are carried with the water through the crevices and are enveloped in the mud formed as the water rushes through the loose ashes and soil. The almost extinguished volcano of Imbaburu ejected in 1691 so great a quantity of fish, that fevers which prevailed at the period were attributed to the effluvia from the putrid animal matter. The most considerable volcanos of the Andes are situated not far from each other in the province of Quito. These are, Cayambe, Cotopaxi, Pichincha, Antisana, L'Altar, and Tunguragua. Of all the summits of the Andes the height of which has been determined with any degree of precision, the volcano of Cayambe is the most lofty after Chimborazo being 19,625 feet. Its form, like the volcano called the Nevada de Tolima, is that of a truncated cone, and it is one of the most beautiful and majestic of all those which surround the city of Quito. Its summit is crossed by the line of the equator, and it stands, says Humboldt, like one of the colossal and eternal monuments placed by the hand of nature to mark the grand divisions of the globe. According to a very probable tradition of the Indians of Lican, the mountain called L'Altar, or in the Quichoa tongue, Capa-Urcu, was once higher than Chimborazo, but in the reign of Ouainia Abomatha a prodigious eruption took place, which lasted eight years, and broke it down. The summit of this remarkable mountain presents a series of sharp pinnacles and needles, and when the rays of the setting sun strike upon these ice-clad ruins, the most magnificent play of colours is produced. The volcano of Antisana, which is 19,120 feet high, appears never to have had its summit pierced, the lava having burst forth from an opening in the side. Pichincha, which is 15,920 feet high, has a crater, the edges of which are covered with pumice, but it does not appear to have ejected a current of lava since the formation of the adjoining vallies. The volcano of Cotopaxi is the most lofty of all the volcanos of the Andes which have been in a state of activity in modern times. Its height is such (18,858 feet) that it would exceed by 2600 feet the summit of Vesuvius if that volcano were placed on the top of the peak of Teneriffe. It is the most dreaded of all the volcanos of Quito, because its eruptions have been the most frequent and the most devastating in their effects. In 1738 the flames rose nearly three thousand feet above the edge of the crater. In 1744 the sound of the explosions was so great as to be heard at a distance of five hundred and fifty miles. On the 4th of April, 1768, the quantity of ashes thrown out was so great that in the towns of Hambato and Tacunga such a degree of darkness was produced as to oblige the inhabitants to go about with lanterns for many hours in the day-time. The eruption of January, 1803, was preceded by sudden melting of the snow which covers the mountain. For twenty years no smoke nor visible vapour had issued from the crater, but in a single night the internal fires became so active, that at sunrise the external walls of the cone were observed to be black and bare, their mantle of snow having been dissolved by the

so much in the precious metals as the Andes, both in South
America and in the prolongation of the chain northward
Mines. No mountains in any part of the globe abound
into Mexico. For three centuries their riches have been
spread over every part of the globe to which civilization has
extended, and it is probable, that if improved systems of
working the mines were introduced, where there are no
natural obstacles to their adoption, the produce would be
immensely increased.

rock, through which its veins must be followed by extensive
subterraneous excavations, nor is it met with in ores, in
GOLD is seldom found, like other metals, in the solid
combination with foreign substances, which can only he
separated from the pure metal by long and expensive
operations. It is always found in the metallic state, and in
a great degree of purity; by far the largest quantity is
collected in the form of grains and small rounded lumps,
from the disintegration of rocks containing the metal, and
most probably in the form of slender veins.
scattered through alluvial soils, which have been derived
great depth, and that soil frequently extends a great way
on both sides of the river, the deposits of a long succession
courses of rivers are usually composed of alluvial soil to a
The water-
of ages; the grains of gold are disseminated through the
whole of this alluvium. The places chosen for digging into
that auriferous soil are called lavaderos, because the grave

END OF VOLUME THE FIRST.

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