Proceeding up the ravine, we come to another mass [R] of andesite; and

beyond this, we again have a very thick, stratified porphyritic

formation [S], dipping at a small angle eastward, and forming the basal

part of the main Cordillera. I did not ascend the ravine any higher;

but here, near Castano, I examined several sections, of which I will

not give the details, only observing, that the porphyritic beds, or

submarine lavas, preponderate greatly in bulk over the alternating

sedimentary layers, which have been but little metamorphosed: these

latter consist of fine-grained red tuffs and of whitish volcanic

grit-stones, together with much of a singular, compact rock, having an

almost crystalline basis, finely brecciated with red and green

fragments, and occasionally including a few large pebbles. The

porphyritic lavas are highly amygdaloidal, both on their upper and

lower surfaces; they consist chiefly of claystone porphyry, but with

one common variety, like some of the streams at the Puente del Inca,

having a grey mottled basis, abounding with crystals of red hydrous

oxide of iron, green ones apparently of epidote, and a few glassy ones

of feldspar. This pile of strata differs considerably from the basal

strata of the Cordillera in Central Chile, and may possibly belong to

the upper and gypseous series: I saw, however, in the bed of the

valley, one fragment of porphyritic breccia-conglomerate, exactly like

those great masses met with in the more southern parts of Chile.

Finally, I must observe, that though I have described between the town

of Copiapo and the western flank of the main Cordillera seven or eight

axes of elevation, extending nearly north and south, it must not be

supposed that they all run continuously for great distances. As was

stated to be the case in our sections across the Cordillera of Central

Chile, so here most of the lines of elevation, with the exception of

the first, third, and fifth, are very short. The stratification is

everywhere disturbed and intricate; nowhere have I seen more numerous

faults and dikes. The whole district, from the sea to the Cordillera,

is more or less metalliferous; and I heard of gold, silver, copper,

lead, mercury, and iron veins. The metamorphic action, even in the

lower strata, has certainly been far less here than in Central Chile.

VALLEY OF THE DESPOBLADO.

This great barren valley, which has already been alluded to, enters the

main valley of Copiapo a little above the town: it runs at first

northerly, then N.E., and more easterly into the Cordillera; I followed

its dreary course to the foot of the first main ridge. I will not give

a detailed section, because it would be essentially similar to that

already given, and because the stratification is exceedingly

complicated. After leaving the plutonic hills near the town, I met

first, as in the main valley, with the gypseous formation, having the

same diversified character as before, and soon afterwards with masses

of porphyritic conglomerate, about one thousand feet in thickness. In

the lower part of this formation there were very thick beds composed of

fragments of claystone porphyries, both angular and rounded, with the

smaller ones partially blended together and the basis rendered

porphyritic; these beds separated distinct streams, from sixty to

eighty feet in thickness, of claystone lavas. Near Paipote, also, there

was much true porphyritic breccia-conglomerate: nevertheless, few of

these masses were metamorphosed to the same degree with the

corresponding formation in Central Chile. I did not meet in this valley

with any true andesite, but only with imperfect andesitic porphyry,

including large crystals of hornblende: numerous as have been the

varieties of intrusive porphyries already mentioned, there were here

mountains composed of a new kind, having a compact, smooth,

cream-coloured basis, including only a few crystals of feldspar, and

mottled with dendritic spots of oxide of iron. There were also some

mountains of a porphyry with a brick-red basis, containing irregular,

often lens-shaped, patches of compact feldspar, and crystals of

feldspar, which latter to my surprise I find to be orthite.

At the foot of the first ridge of the main Cordillera, in the ravine of

Maricongo, and at an elevation which, from the extreme coldness and

appearance of the vegetation, I estimated at about ten thousand feet, I

found beds of white sandstone and of limestone including the Pecten

Dufreynoyi, Terebratula aenigma, and some Gryphites. This ridge throws

the water on the one hand into the Pacific, and on the other, as I was

informed, into a great gravel-covered, basin-like plain, including a

salt- lake, and without any drainage-exit. In crossing the Cordillera

by this Pass, it is said that three principal ridges must be traversed,

instead of two, or only one as in Central Chile.

The crest of this first main ridge and the surrounding mountains, with

the exception of a few lofty pinnacles, are capped by a great thickness

of a horizontally stratified, tufaceous deposit. The lowest bed is of a

pale purple colour, hard, fine-grained, and full of broken crystals of

feldspar and scales of mica. The middle bed is coarser, and less hard,

and hence weathers into very sharp pinnacles; it includes very small

fragments of granite, and innumerable ones of all sizes of grey

vesicular trachyte, some of which were distinctly rounded. The

uppermost bed is about two hundred feet in thickness, of a darker

colour and apparently hard: but I had not time to ascend to it. These

three horizontal beds may be seen for the distance of many leagues,

especially westward or in the direction of the Pacific, capping the

summits of the mountains, and standing on the opposite sides of the

immense valleys at exactly corresponding heights. If united they would

form a plain, inclined very slightly towards the Pacific; the beds

become thinner in this direction, and the tuff (judging from one point

to which I ascended, some way down the valley) finer-grained and of

less specific gravity, though still compact and sonorous under the

hammer. The gently inclined, almost horizontal stratification, the

presence of some rounded pebbles, and the compactness of the lowest

bed, though rendering it probable, would not have convinced me that

this mass had been of subaqueous origin, for it is known that volcanic

ashes falling on land and moistened by rain often become hard and

stratified; but beds thus originating, and owing their consolidation to

atmospheric moisture, would have covered almost equally every

neighbouring summit, high and low, and would not have left those above

a certain exact level absolutely bare; this circumstance seems to me to

prove that the volcanic ejections were arrested at their present,

widely extended, equable level, and there consolidated by some other

means than simple atmospheric moisture; and this no doubt must have

been a sheet of water. A lake at this great height, and without a

barrier on any one side, is out of the question; consequently we must

conclude that the tufaceous matter was anciently deposited beneath the

sea. It was certainly deposited before the excavation of the valleys,

or at least before their final enlargement (I have endeavoured to show

in my “Journal” etc. (2nd edition) page 355, that this arid valley was

left by the retreating sea, as the land slowly rose, in the state in

which we now see it.); and I may add, that Mr. Lambert, a gentleman

well acquainted with this country, informs me, that in ascending the

ravine of Santandres (which branches off from the Despoblado) he met

with streams of lava and much erupted matter capping all the hills of

granite and porphyry, with the exception of some projecting points; he

also remarked that the valleys had been excavated subsequently to these

eruptions.

This volcanic formation, which I am informed by Mr. Lambert extends far

northward, is of interest, as typifying what has taken place on a

grander scale on the corresponding western side of the Cordillera of

Peru. Under another point of view, however, it possesses a far higher

interest, as confirming that conclusion drawn from the structure of the

fringes of stratified shingle which are prolonged from the plains at

the foot of the Cordillera far up the valleys,—namely, that this great

range has been elevated in mass to a height of between eight and nine

thousand feet (I may here mention that on the south side of the main

valley of Copiapo, near Potrero Seco, the mountains are capped by a

thick mass of horizontally stratified shingle, at a height which I

estimated at between fifteen hundred and two thousand feet above the

bed of the valley. This shingle, I believe, forms the edge of a wide

plain, which stretches southwards between two mountain ranges.); and

now, judging from this tufaceous deposit, we may conclude that the

horizontal elevation has been in the district of Copiapo about ten

thousand feet.

(FIGURE 24.)

In the valley of the Despoblado, the stratification, as before remarked

has been much disturbed, and in some points to a greater degree than I

have anywhere else seen. I will give two cases: a very thick mass of

thinly stratified red sandstone, including beds of conglomerate, has

been crushed together (as represented in Figure 24) into a yoke or

urn-formed trough, so that the strata on both sides have been folded

inwards: on the right hand the properly underlying porphyritic

claystone conglomerate is seen overlying the sandstone, but it soon

becomes vertical, and then is inclined towards the trough, so that the

beds radiate like the spokes of a wheel: on the left hand, the inverted

porphyritic conglomerate also assumes a dip towards the trough, not

gradually, as on the right hand, but by means of a vertical fault and

synclinal break; and a little still further on towards the left, there

is a second great oblique fault (both shown by the arrow- lines), with

the strata dipping to a directly opposite point; these mountains are

intersected by infinitely numerous dikes, some of which can be seen to

rise from hummocks of greenstone, and can be traced for thousands of

feet. In the second case, two low ridges trend together and unite at

the head of a little wedge-shaped valley: throughout the right- hand

ridge, the strata dip at 45 degrees to the east; in the left-hand

ridge, we have the very same strata and at first with exactly the same

dip; but in following this ridge up the valley, the strata are seen

very regularly to become more and more inclined until they stand

vertical, they then gradually fall over (the basset edges forming

symmetrical serpentine lines along the crest), till at the very head of

the valley they are reversed at an angle of 45 degrees: so that at this

point the beds have been turned through an angle of 135 degrees; and

here there is a kind of anticlinal axis, with the strata on both sides

dipping to opposite points at an angle of 45 degrees, but those on the

left hand upside down.

ON THE ERUPTIVE SOURCES OF THE PORPHYRITIC CLAYSTONE AND GREENSTONE

LAVAS.

In Central Chile, from the extreme metamorphic action, it is in most

parts difficult to distinguish between the streams of porphyritic lava

and the porphyritic breccia-conglomerate, but here, at Copiapo, they

are generally perfectly distinct, and in the Despoblado, I saw for the

first time, two great strata of purple claystone porphyry, after having

been for a considerable space closely united together, one above the

other, become separated by a mass of fragmentary matter, and then both

thin out;—the lower one more rapidly than the upper and greater stream.

Considering the number and thickness of the streams of porphyritic

lava, and the great thickness of the beds of breccia-conglomerate,

there can be little doubt that the sources of eruption must originally

have been numerous: nevertheless, it is now most difficult even to

conjecture the precise point of any one of the ancient submarine

craters. I have repeatedly observed mountains of porphyries, more or

less distinctly stratified towards their summits or on their flanks,

without a trace of stratification in their central and basal parts: in

most cases, I believe this is simply due either to the obliterating

effects of metamorphic action, or to such parts having been mainly

formed of intrusive porphyries, or to both causes conjoined; in some

instances, however, it appeared to me very probable that the great

central unstratified masses of porphyry were the now partially denuded

nuclei of the old submarine volcanoes, and that the stratified parts

marked the points whence the streams flowed. In one case alone, and it

was in this Valley of the Despoblado, I was able actually to trace a

thick stratum of purplish porphyry, which for a space of some miles

conformably overlay the usual alternating beds of breccia-conglomerates

and claystone lavas, until it became united with, and blended into, a

mountainous mass of various unstratified porphyries.

The difficulty of tracing the streams of porphyries to their ancient

and doubtless numerous eruptive sources, may be partly explained by the

very general disturbance which the Cordillera in most parts has

suffered; but I strongly suspect that there is a more specific cause,

namely, THAT THE ORIGINAL POINTS OF ERUPTION TEND TO BECOME THE POINTS

OF INJECTION. This in itself does not seem improbable; for where the

earth’s crust has once yielded, it would be liable to yield again,

though the liquified intrusive matter might not be any longer enabled

to reach the submarine surface and flow as lava. I have been led to

this conclusion, from having so frequently observed that, where part of

an unstratified mountain-mass resembled in mineralogical character the

adjoining streams or strata, there were several other kinds of

intrusive porphyries and andesitic rocks injected into the same point.

As these intrusive mountain-masses form most of the axes-lines in the

Cordillera, whether anticlinal, uniclinal, or synclinal, and as the

main valleys have generally been hollowed out along these lines, the

intrusive masses have generally suffered much denudation. Hence they

are apt to stand in some degree isolated, and to be situated at the

points where the valleys abruptly bend, or where the main tributaries

enter. On this view of there being a tendency in the old points of

eruption to become the points of subsequent injection and disturbance,

and consequently of denudation, it ceases to be surprising that the

streams of lava in the porphyritic claystone conglomerate formation,

and in other analogous cases, should most rarely be traceable to their

actual sources.

IQUIQUE, SOUTHERN PERU.

Differently from what we have seen throughout Chile, the coast here is

formed not by the granitic series, but by an escarpment of the

porphyritic conglomerate formation, between two and three thousand feet

in height. (The lowest point, where the road crosses the

coast-escarpment, is 1,900 feet by the barometer above the level of the

sea.) I had time only for a very short examination; the chief part of

the escarpment appears to be composed of various reddish and purple,

sometimes laminated, porphyries, resembling those of Chile; and I saw

some of the porphyritic breccia-conglomerate; the stratification

appeared but little inclined. The uppermost part, judging from the

rocks near the famous silver mine of Huantajaya, consists of laminated,

impure, argillaceous, purplish-grey limestone, associated, I believe,

with some purple sandstone. (Mr. Bollaert has described “Geological

Proceedings” volume 2 page 598, a singular mass of stratified detritus,

gravel, and sand, eighty-one yards in thickness, overlying the

limestone, and abounding with loose masses of silver ore. The miners

believe that they can attribute these masses to their proper veins.) In

the limestone shells are found: the three following species were given

me:—

Lucina Americana, E. Forbes. Terebratula inca, E. Forbes. Terebratula

aenigma, D’Orbigny.

This latter species we have seen associated with the fossils of which

lists have been given in this chapter, in two places in the valley of

Coquimbo, and in the ravine of Maricongo at Copiapo. Considering this

fact, and the superposition of these beds on the porphyritic

conglomerate formation; and, as we shall immediately see, from their

containing much gypsum, and from their otherwise close general

resemblance in mineralogical nature with the strata described in the

valley of Copiapo, I have little doubt that these fossiliferous beds of

Iquique belong to the great cretaceo-oolitic formation of Northern

Chile. Iquique is situated seven degrees latitude north of Copiapo; and

I may here mention, that an Ammonites, nov. species, and an Astarte,

nov. species, were given me from the Cerro Pasco, about ten degrees of

latitude north of Iquique, and M. D’Orbigny thinks that they probably

indicate a Neocomian formation. Again, fifteen degrees of latitude

northward, in Colombia, there is a grand fossiliferous deposit, now

well known from the labours of Von Buch, Lea, d’Orbigny, and Forbes,

which belongs to the earlier stages of the cretaceous system. Hence,

bearing in mind the character of the few fossils from Tierra del Fuego,

there is some evidence that a great portion of the stratified deposits

of the whole vast range of the South American Cordillera belongs to

about the same geological epoch.

Proceeding from the coast escarpment inwards, I crossed, in a space of

about thirty miles, an elevated undulatory district, with the beds

dipping in various directions. The rocks are of many kinds,—white

laminated, sometimes siliceous sandstone,—purple and red sandstone,

sometimes so highly calcareous as to have a crystalline

fracture,—argillaceous limestone,—black calcareous slate-rock, like

that so often described at Copiapo and other places,—thinly laminated,

fine-grained, greenish, indurated, sedimentary, fusible rocks,

approaching in character to the so- called pseudo-honestone of Chile,

including thin contemporaneous veins of gypsum,—and lastly, much

calcareous, laminated porcelain jasper, of a green colour, with red

spots, and of extremely easy fusibility: I noticed one conformable

stratum of a freckled-brown, feldspathic lava. I may here mention that

I heard of great beds of gypsum in the Cordillera. The only novel point

in this formation, is the presence of innumerable thin layers of

rock-salt, alternating with the laminated and hard, but sometimes

earthy, yellowish, or bright red and ferruginous sandstones. The

thickest layer of salt was only two inches, and it thinned out at both

ends. On one of these saliferous masses I noticed a stratum about

twelve feet thick, of dark-brown, hard brecciated, easily fusible rock,

containing grains of quartz and of black oxide of iron, together with

numerous imperfect fragments of shells. The problem of the origin of

salt is so obscure, that every fact, even geographical position, is

worth recording. (It is well known that stratified salt is found in

several places on the shores of Peru. The island of San Lorenzo, off

Lima, is composed of a pile of thin strata, about eight hundred feet in

thickness, composed of yellowish and purplish, hard siliceous, or

earthy sandstones, alternating with thin layers of shale, which in

places passes into a greenish, semi-porcellanic, fusible rock. There

are some thin beds of reddish mudstone, and soft ferruginous

rotten-stones, with layers of gypsum. In nearly all these varieties,

especially in the softer sandstones, there are numerous thin seams of

rock-salt: I was informed that one layer has been found two inches in

thickness. The manner in which the minutest fissures of the dislocated

beds have been penetrated by the salt, apparently by subsequent

infiltration, is very curious. On the south side of the island, layers

of coal and of impure limestone have been discovered. Hence we here

have salt, gypsum, and coal associated together. The strata include

veins of quartz, carbonate of lime, and iron pyrites; they have been

dislocated by an injected mass of greenish-brown feldspathic trap. Not

only is salt abundant on the extreme western limits of the district

between the Cordillera and the Pacific, but, according to Helms, it is

found in the outlying low hills on the eastern flank of the Cordillera.

These facts appear to me opposed to the theory, that rock-salt is due

to the sinking of water, charged with salt, in mediterranean spaces of

the ocean. The general character of the geology of these countries

would rather lead to the opinion, that its origin is in some way

connected with volcanic heat at the bottom of the sea: see on this

subject Sir R. Murchison “Anniversary Address to the Geological

Society” 1843 page 65.) With the exception of these saliferous beds,

most of the rocks as already remarked, present a striking general

resemblance with the upper parts of the gypseous or cretaceo-oolitic

formation of Chile.

METALLIFEROUS VEINS.

I have only a few remarks to make on this subject: in nine mining

districts, some of them of considerable extent, which I visited in

CENTRAL Chile, I found the PRINCIPAL veins running from between [N. and

N.W.] to [S. and S.E.] (These mining districts are Yaquil near

Nancagua, where the direction of the chief veins, to which only in all

cases I refer, is north and south; in the Uspallata range, the

prevailing line is N.N.W. and S.S.E.; in the C. de Prado, it is N.N.W.

and S.S.E.; near Illapel, it is N. by W. and S. by E.; at Los Hornos

the direction varies from between [N. and N.W.] to [S. and S.E.]; at

the C. de los Hornos (further northward), it is N.N.W. and S.S.E.; at

Panuncillo, it is N.N.W. and S.S.E.; and, lastly, at Arqueros, the

direction is N.W. and S.E.): in some other places, however, their

courses appeared quite irregular, as is said to be generally the case

in the whole valley of Copiapo: at Tambillos, south of Coquimbo, I saw

one large copper vein extending east and west. It is worthy of notice,

that the foliation of the gneiss and mica-slate, where such rocks

occur, certainly tend to run like the metalliferous veins, though often

irregularly, in a direction a little westward of north. At Yaquil, I

observed that the principal auriferous veins ran nearly parallel to the

grain or imperfect cleavage of the surrounding GRANITIC rocks. With

respect to the distribution of the different metals, copper, gold, and

iron are generally associated together, and are most frequently found

(but with many exceptions, as we shall presently see) in the rocks of

the lower series, between the Cordillera and the Pacific, namely, in

granite, syenite, altered feldspathic clay-slate, gneiss, and as near

Guasco mica-schist. The copper-ores consist of sulphurets, oxides, and

carbonates, sometimes with laminae of native metal: I was assured that

in some cases (as at Panuncillo S.E. of Coquimbo), the upper part of

the same vein contains oxides, and the lower part sulphurets of copper.

(The same fact has been observed by Mr. Taylor in Cuba: “London

Philosophical Journal” volume 11 page 21.) Gold occurs in its native

form; it is believed that, in many cases, the upper part of the vein is

the most productive part: this fact probably is connected with the

abundance of this metal in the stratified detritus of Chile, which must

have been chiefly derived from the degradation of the upper portions of

the rocks. These superficial beds of well-rounded gravel and sand,

containing gold, appeared to me to have been formed under the sea close

to the beach, during the slow elevation of the land: Schmidtmeyer

remarks that in Chile gold is sought for in shelving banks at the

height of some feet on the sides of the streams, and not in their beds,

as would have been the case had this metal been deposited by common

alluvial action. (“Travels in Chile” page 29.) Very frequently the

copper-ores, including some gold, are associated with abundant

micaceous specular iron. Gold is often found in iron-pyrites: at two

gold mines at Yaquil (near Nancagua), I was informed by the proprietor

that in one the gold was always associated with copper-pyrites, and in

the other with iron-pyrites: in this latter case, it is said that if

the vein ceases to contain iron-pyrites, it is yet worth while to

continue the search, but if the iron-pyrites, when it reappears, is not

auriferous, it is better at once to give up working the vein. Although

I believe copper and gold are most frequently found in the lower

granitic and metamorphic schistose series, yet these metals occur both

in the porphyritic conglomerate formation (as on the flanks of the Bell

of Quillota and at Jajuel), and in the superincumbent strata. At Jajuel

I was informed that the copper-ore, with some gold, is found only in

the greenstones and altered feldspathic clay-slate, which alternate

with the purple porphyritic conglomerate. Several gold veins and some

of copper- ore are worked in several parts of the Uspallata range, both

in the metamorphosed strata, which have been shown to have been of

probably subsequent origin to the Neocomian or gypseous formation of

the main Cordillera, and in the intrusive andesitic rocks of that

range. At Los Hornos (N.E. of Illapel), likewise, there are numerous

veins of copper- pyrites and of gold, both in the strata of the

gypseous formation and in the injected hills of andesite and various

porphyries.

Silver, in the form of a chloride, sulphuret, or an amalgam, or in its

native state, and associated with lead and other metals, and at

Arqueros with pure native copper, occurs chiefly in the upper great

gypseous or cretaceo-oolitic formation which forms probably the richest

mass in Chile. We may instance the mining districts of Arqueros near

Coquimbo, and of nearly the whole valley of Copiapo, and of Iquique

(where the principal veins run N.E. by E. and S.W. by W.), in Peru.

Hence comes Molina’s remark, that silver is born in the cold and

solitary deserts of the Upper Cordillera. There are, however,

exceptions to this rule: at Paral (S.E. of Coquimbo) silver is found in

the porphyritic conglomerate formation; as I suspect is likewise the

case at S. Pedro de Nolasko in the Peuquenes Pass. Rich argentiferous

lead is found in the clay-slate of the Uspallata range; and I saw an

old silver-mine in a hill of syenite at the foot of the Bell of

Quillota: I was also assured that silver has been found in the

andesitic and porphyritic region between the town of Copiapo and the

Pacific. I have stated in a previous part of this chapter, that in two

neighbouring mines at Arqueros the veins in one were productive when

they traversed the singular green sedimentary beds, and unproductive

when crossing the reddish beds; whereas at the other mine exactly the

reverse takes place; I have also described the singular and rare case

of numerous particles of native silver and of the chloride being

disseminated in the green rock at the distance of a yard from the vein.

Mercury occurs with silver both at Arqueros and at Copiapo: at the base

of C. de los Hornos (S.E. of Coquimbo, a different place from Los

Hornos, before mentioned) I saw in a syenitic rock numerous quartzose

veins, containing a little cinnabar in nests: there were here other

parallel veins of copper and of a ferrugino-auriferous ore. I believe

tin has never been found in Chile.

From information given me by Mr. Nixon of Yaquil (At the Durazno mine,

the gold is associated with copper-pyrites, and the veins contain large

prisms of plumbago. Crystallised carbonate of lime is one of the

commonest minerals in the matrix of the Chilean veins.), and by others,

it appears that in Chile those veins are generally most permanently

productive, which, consisting of various minerals (sometimes differing

but slightly from the surrounding rocks), include parallel strings RICH

in metals; such a vein is called a veta real. More commonly the mines

are worked only where one, two, or more thin veins or strings running

in a different direction, intersect a POOR “veta real:” it is

unanimously believed that at such points of intersection (cruceros),

the quantity of metal is much greater than that contained in other

parts of the intersecting veins. In some cruceros or points of

intersection, the metals extend even beyond the walls of the main,

broad, stony vein. It is said that the greater the angle of

intersection, the greater the produce; and that nearly parallel strings

attract each other; in the Uspallata range, I observed that numerous

thin auri-ferruginous veins repeatedly ran into knots, and then

branched out again. I have already described the remarkable manner in

which rocks of the Uspallata range are indurated and blackened (as if

by a blast of gunpowder) to a considerable distance from the metallic

veins.

Finally, I may observe, that the presence of metallic veins seems

obviously connected with the presence of intrusive rocks, and with the

degree of metamorphic action which the different districts of Chile

have undergone. (Sir R. Murchison and his fellow travellers have given

some striking facts on this subject in their account of the Ural

Mountains (“Geological Proceedings” volume 3 page 748.) Such

metamorphosed areas are generally accompanied by numerous dikes and

injected masses of andesite and various porphyries: I have in several

places traced the metalliferous veins from the intrusive masses into

the encasing strata. Knowing that the porphyritic conglomerate

formation consists of alternate streams of submarine lavas and of the

debris of anciently erupted rocks, and that the strata of the upper

gypseous formation sometimes include submarine lavas, and are composed

of tuffs, mudstones, and mineral substances, probably due to volcanic

exhalations,—the richness of these strata is highly remarkable when

compared with the erupted beds, often of submarine origin, but NOT

METAMORPHOSED, which compose the numerous islands in the Pacific,

Indian, and Atlantic Oceans; for in these islands metals are entirely

absent, and their nature even unknown to the aborigines.

A SUMMARY OF THE GEOLOGICAL HISTORY OF THE CHILEAN CORDILLERA, AND OF

THE SOUTHERN PARTS OF SOUTH AMERICA.

We have seen that the shores of the Pacific, for a space of 1,200 miles

from Tres Montes to Copiapo, and I believe for a very much greater

distance, are composed, with the exception of the tertiary basins, of

metamorphic schists, plutonic rocks, and more or less altered

clay-slate. On the floor of the ocean thus constituted, vast streams of

various purplish claystone and greenstone porphyries were poured forth,

together with great alternating piles of angular and rounded fragments

of similar rocks ejected from the submarine craters. From the

compactness of the streams and fragments, it is probable that, with the

exception of some districts in Northern Chile, the eruptions took place

in profoundly deep water. The orifices of eruption appear to have been

studded over a breadth, with some outliers, of from fifty to one

hundred miles: and closely enough together, both north and south, and

east and west, for the ejected matter to form a continuous mass, which

in Central Chile is more than a mile in thickness. I traced this

mould-like mass, for only 450 miles; but judging from what I saw at

Iquique, from specimens, and from published accounts, it appears to

have a manifold greater length. In the basal parts of the series, and

especially towards the flanks of the range, mud, since converted into a

feldspathic slaty rock, and sometimes into greenstone, was occasionally

deposited between the beds of erupted matter: with this exception the

uniformity of the porphyritic rocks is very remarkable.

At the period when the claystone and greenstone porphyries nearly or

quite ceased being erupted, that great pile of strata which, from often

abounding with gypsum, I have generally called the gypseous formation

was deposited, and feldspathic lavas, together with other singular

volcanic rocks, were occasionally poured forth: I am far from

pretending that any distinct line of demarcation can be drawn between

this formation and the underlying porphyries and porphyritic

conglomerate, but in a mass of such great thickness, and between beds

of such widely different mineralogical nature, some division was

necessary. At about the commencement of the gypseous period, the bottom

of the sea here seems first to have been peopled by shells, not many in

kind, but abounding in individuals. At the P. del Inca the fossils are

embedded near the base of the formation; in the Peuquenes range, at

different levels, halfway up, and even higher in the series; hence, in

these sections, the whole pile of strata belongs to the same period:

the same remark is applicable to the beds at Copiapo, which attain a

thickness of between seven and eight thousand feet. The fossil shells

in the Cordillera of Central Chile, in the opinion of all the

palaeontologists who have examined them, belong to the earlier stages

of the cretaceous system; whilst in Northern Chile there is a most

singular mixture of cretaceous and oolitic forms: from the geological

relations, however, of these two districts, I cannot but think that

they all belong to nearly the same epoch, which I have provisionally

called cretaceo-oolitic.

The strata in this formation, composed of black calcareous shaly-rocks

of red and white, and sometimes siliceous sandstone, of coarse

conglomerates, limestones, tuffs, dark mudstones, and those singular

fine-grained rocks which I have called pseudo-honestones, vast beds of

gypsum, and many other jaspery and scarcely describable varieties, vary

and replace each other in short horizontal distances, to an extent, I

believe, unequalled even in any tertiary basin. Most of these

substances are easily fusible, and have apparently been derived either

from volcanoes still in quiet action, or from the attrition of volcanic

products. If we picture to ourselves the bottom of the sea, rendered

uneven in an extreme degree, with numerous craters, some few

occasionally in eruption, but the greater number in the state of

solfataras, discharging calcareous, siliceous, ferruginous matters, and

gypsum or sulphuric acid to an amount surpassing, perhaps, even the

existing sulphureous volcanoes of Java (Von Buch’s “Description

Physique des Iles Canaries” page 428.), we shall probably understand

the circumstances under which this singular pile of varying strata was

accumulated. The shells appear to have lived at the quiescent periods

when only limestone or calcareo-argillaceous matter was depositing.

From Dr. Gillies’ account, this gypseous or cretaceo-oolitic formation

extends as far south as the Pass of Planchon, and I followed it

northward at intervals for 500 miles: judging from the character of the

beds with the Terebratula aenigma, at Iquique, it extends from four to

five hundred miles further: and perhaps even for ten degrees of

latitude north of Iquique to the Cerro Pasco, not far from Lima: again,

we know that a cretaceous formation, abounding with fossils, is largely

developed north of the equator, in Colombia: in Tierra del Fuego, at

about this same period, a wide district of clay-slate was deposited,

which in its mineralogical characters and external features, might be

compared to the Silurian regions of North Wales. The gypseous

formation, like that of the porphyritic breccia- conglomerate on which

it rests, is of inconsiderable breadth; though of greater breadth in

Northern than in Central Chile.

As the fossil shells in this formation are covered, in the Peuquenes

ridge, by a great thickness of strata; at the Puente del Inca, by at

least five thousand feet; at Coquimbo, though the superposition there

is less plainly seen, by about six thousand feet; and at Copiapo,

certainly by five or six thousand, and probably by seven thousand feet

(the same species there recurring in the upper and lower parts of the

series), we may feel confident that the bottom of the sea subsided

during this cretaceo-oolitic period, so as to allow of the accumulation

of the superincumbent submarine strata. This conclusion is confirmed

by, or perhaps rather explains, the presence of the many beds at many

levels of coarse conglomerate, the well- rounded pebbles in which we

cannot believe were transported in very deep water. Even the underlying

porphyries at Copiapo. with their highly amygdaloidal surfaces, do not

appear to have flowed under great pressure. The great sinking movement

thus plainly indicated, must have extended in a north and south line

for at least four hundred miles, and probably was co- extensive with

the gypseous formation.

The beds of conglomerate just referred to, and the extraordinarily

numerous silicified trunks of fir-trees at Los Hornos, perhaps at

Coquimbo and at two distant points in the valley of Copiapo, indicate

that land existed at this period in the neighbourhood. This land, or

islands, in the northern part of the district of Copiapo, must have

been almost exclusively composed, judging from the nature of the

pebbles of granite: in the southern parts of Copiapo, it must have been

mainly formed of claystone porphyries, with some mica-schist, and with

much sandstone and jaspery rocks exactly like the rocks in the gypseous

formation, and no doubt belonging to its basal series. In several other

places also, during the accumulation of the gypseous formation, its

basal parts and the underlying porphyritic conglomerate must likewise

have been already partially upheaved and exposed to wear and tear; near

the Puente del Inca and at Coquimbo, there must have existed masses of

mica-schist or some such rock, whence were derived the many small

pebbles of opaque quartz. It follows from these facts, that in some

parts of the Cordillera the upper beds of the gypseous formation must

lie unconformably on the lower beds; and the whole gypseous formation,

in parts, unconformably on the porphyritic conglomerate; although I saw

no such cases, yet in many places the gypseous formation is entirely

absent; and this, although no doubt generally caused by quite

subsequent denudation, may in others be due to the underlying

porphyritic conglomerate having been locally upheaved before the

deposition of the gypseous strata, and thus having become the source of

the pebbles of porphyry embedded in them. In the porphyritic

conglomerate formation, in its lower and middle parts, there is very

rarely any evidence, with the exception of the small quartz pebbles at

Jajuel near Aconcagua, and of the single pebble of granite at Copiapo,

of the existence of neighbouring land: in the upper parts, however, and

especially in the district of Copiapo, the number of thoroughly

well-rounded pebbles of compact porphyries make me believe, that, as

during the prolonged accumulation of the gypseous formation the lower

beds had already been locally upheaved and exposed to wear and tear, so

it was with the porphyritic conglomerate. Hence in following thus far

the geological history of the Cordillera, it may be inferred that the

bed of a deep and open, or nearly open, ocean was filled up by

porphyritic eruptions, aided probably by some general and some local

elevations, to that comparatively shallow level at which the cretaceo-

oolitic shells first lived. At this period, the submarine craters

yielded at intervals a prodigious supply of gypsum and other mineral

exhalations, and occasionally, in certain places poured forth lavas,

chiefly of a feldspathic nature: at this period, islands clothed with

fir-trees and composed of porphyries, primary rocks, and the lower

gypseous strata had already been locally upheaved, and exposed to the

action of the waves;—the general movement, however, at this time having

been over a very wide area, one of slow subsidence, prolonged till the

bed of the sea sank several thousand feet.

In Central Chile, after the deposition of a great thickness of the

gypseous strata, and after their upheaval, by which the Cumbre and

adjoining ranges were formed, a vast pile of tufaceous matter and

submarine lava was accumulated, where the Uspallata chain now stands;

also after the deposition and upheaval of the equivalent gypseous

strata of the Peuquenes range, the great thick mass of conglomerate in

the valley of Tenuyan was accumulated: during the deposition of the

Uspallata strata, we know absolutely, from the buried vertical trees,

that there was a subsidence of some thousand feet; and we may infer

from the nature of the conglomerate in the valley of Tenuyan, that a

similar and perhaps contemporaneous movement there took place. We have,

then, evidence of a second great period of subsidence; and, as in the

case of the subsidence which accompanied the accumulation of the

cretaceo-oolitic strata, so this latter subsidence appears to have been

complicated by alternate or local elevatory movement— for the vertical

trees, buried in the midst of the Uspallata strata, must have grown on

dry land, formed by the upheaval of the lower submarine beds. Presently

I shall have to recapitulate the facts, showing that at a still later

period, namely, at nearly the commencement of the old tertiary deposits

of Patagonia and of Chile, the continent stood at nearly its present

level, and then, for the third time, slowly subsided to the amount of

several hundred feet, and was afterwards slowly re-uplifted to its

present level.

The highest peaks of the Cordillera appear to consist of active or more

commonly dormant volcanoes,—such as Tupungato, Maypu, and Aconcagua,

which latter stands 23,000 feet above the level of the sea, and many

others. The next highest peaks are formed of the gypseous and

porphyritic strata, thrown into vertical or highly inclined positions.

Besides the elevation thus gained by angular displacements, I infer,

without any hesitation—from the stratified gravel-fringes which gently

slope up the valleys of the Cordillera from the gravel-capped plains at

their base, which latter are connected with the plains, still covered

with recent shells on the coast— that this great range has been

upheaved in mass by a slow movement, to an amount of at least 8,000

feet. In the Despoblado Valley, north of Copiapo, the horizontal

elevation, judging from the compact, stratified tufaceous deposit,

capping the distant mountains at corresponding heights, was about ten

thousand feet. It is very possible, or rather probable, that this

elevation in mass may not have been strictly horizontal, but more

energetic under the Cordillera, than towards the coast on either side;

nevertheless, movements of this kind may be conveniently distinguished

from those by which strata have been abruptly broken and upturned. When

viewing the Cordillera, before having read Mr. Hopkins’s profound

“Researches on Physical Geology,” the conviction was impressed on me,

that the angular dislocations, however violent, were quite subordinate

in importance to the great upward movement in mass, and that they had

been caused by the edges of the wide fissures, which necessarily

resulted from the tension of the elevated area, having yielded to the

inward rush of fluidified rock, and having thus been upturned.

The ridges formed by the angularly upheaved strata are seldom of great

length: in the central parts of the Cordillera they are generally

parallel to each other, and run in north and south lines; but towards

the flanks they often extend more or less obliquely. The angular

displacement has been much more violent in the central than in the

exterior MAIN lines; but it has likewise been violent in some of the

MINOR lines on the extreme flanks. The violence has been very unequal

on the same short lines; the crust having apparently tended to yield on

certain points along the lines of fissures. These points, I have

endeavoured to show, were probably first foci of eruption, and

afterwards of injected masses of porphyry and andesite. (Sir R.

Murchison and his companions state “Geological Proceedings” volume 3

page 747, that no true granite appears in the higher Ural Mountains;

but that syenitic greenstone—a rock closely analogous to our

andesite—is far the most abundant of the intrusive masses.) The close

similarity of the andesitic granites and porphyries, throughout Chile,

Tierra del Fuego, and even in Peru, is very remarkable. The prevalence

of feldspar cleaving like albite, is common not only to the andesites,

but (as I infer from the high authority of Professor G. Rose, as well

as from my own measurements) to the various claystone and greenstone

porphyries, and to the trachytic lavas of the Cordillera. The andesitic

rocks have in most cases been the last injected ones, and they probably

form a continuous dome under this great range: they stand in intimate

relationship with the modern lavas; and they seem to have been the

immediate agent in metamorphosing the porphyritic conglomerate

formation, and often likewise the gypseous strata, to the extraordinary

extent to which they have suffered.

With respect to the age at which the several parallel ridges composing

the Cordillera were upthrown, I have little evidence. Many of them may

have been contemporaneously elevated and injected in the same manner as

in volcanic archipelagoes lavas are contemporaneously ejected on the

parallel lines of fissure. (“Volcanic Islands” etc.) But the pebbles

apparently derived from the wear and tear of the porphyritic

conglomerate formation, which are occasionally present in the upper

parts of this same formation, and are often present in the gypseous

formation, together with the pebbles from the basal parts of the latter

formation in its upper strata, render it almost certain that portions,

we may infer ridges, of these two formations were successively

upheaved. In the case of the gigantic Portillo range, we may feel

almost certain that a preexisting granitic line was upraised (not by a

single blow, as shown by the highly inclined basaltic streams in the

valley on its eastern flank) at a period long subsequent to the

upheavement of the parallel Peuquenes range. (I have endeavoured to

show in my “Journal” 2nd edition page 321, that the singular fact of

the river, which drains the valley between these two ranges, passing

through the Portillo and higher line, is explained by its slow and

subsequent elevation. There are many analogous cases in the drainage of

rivers: see “Edinburgh New Philosophical Journal” volume 28 pages 33

and 44.) Again, subsequently to the upheavement of the Cumbre chain,

that of Uspallata was formed and elevated; and afterwards, I may add,

in the plain of Uspallata, beds of sand and gravel were violently

upthrown. The manner in which the various kinds of porphyries and

andesites have been injected one into the other, and in which the

infinitely numerous dikes of various composition intersect each other,

plainly show that the stratified crust has been stretched and yielded

many times over the same points. With respect to the age of the axes of

elevation between the Pacific and the Cordillera, I know little: but

there are some lines which must—namely, those running north and south

in Chiloe, those eight or nine east and west, parallel, far-extended,

most symmetrical uniclinal lines at P. Rumena, and the short N.W.-S.E.

and N.E.- S.W. lines at Concepcion—have been upheaved long after the

formation of the Cordillera. Even during the earthquake of 1835, when

the linear north and south islet of St. Mary was uplifted several feet

above the surrounding area, we perhaps see one feeble step in the

formation of a subordinate mountain-axis. In some cases, moreover, for

instance, near the baths of Cauquenes, I was forcibly struck with the

small size of the breaches cut through the exterior mountain-ranges,

compared with the size of the same valleys higher up where entering the

Cordillera; and this circumstance appeared to me scarcely explicable,

except on the idea of the exterior lines having been subsequently

upthrown, and therefore having been exposed to a less amount of

denudation. From the manner in which the fringes of gravel are

prolonged in unbroken slopes up the valleys of the Cordillera, I infer

that most of the greater dislocations took place during the earlier

parts of the great elevation in mass: I have, however, elsewhere given

a case, and M. de Tschudi has given another, of a ridge thrown up in

Peru across the bed of a river, and consequently after the final

elevation of the country above the level of the sea. (“Reise in Peru”

Band 2 s.8: Author’s “Journal” 2nd edition page 359.)

Ascending to the older tertiary formations, I will not again

recapitulate the remarks already given at the end of the Fifth

Chapter,—on their great extent, especially along the shores of the

Atlantic—on their antiquity, perhaps corresponding with that of the

eocene deposits of Europe,—on the almost entire dissimilarity, though

the formations are apparently contemporaneous, of the fossils from the

eastern and western coasts, as is likewise the case, even in a still

more marked degree, with the shells now living in these opposite though

approximate seas,—on the climate of this period not having been more

tropical than what might have been expected from the latitudes of the

places under which the deposits occur; a circumstance rendered well

worthy of notice, from the contrast with what is known to have been the

case during the older tertiary periods of Europe, and likewise from the

fact of the southern hemisphere having suffered at a much later period,

apparently at the same time with the northern hemisphere, a colder or

more equable temperature, as shown by the zones formerly affected by

ice-action. Nor will I recapitulate the proofs of the bottom of the

sea, both on the eastern and western coast, having subsided seven or

eight hundred feet during this tertiary period; the movement having

apparently been co-extensive, or nearly co-extensive, with the deposits

of this age. Nor will I again give the facts and reasoning on which the

proposition was founded, that when the bed of the sea is either

stationary or rising, circumstances are far less favourable than when

its level is sinking, to the accumulation of conchiferous deposits of

sufficient thickness, extension, and hardness to resist, when upheaved,

the ordinary vast amount of denudation. We have seen that the highly

remarkable fact of the absence of any EXTENSIVE formations containing

recent shells, either on the eastern or western coasts of the

continent,—though these coasts now abound with living mollusca,—though

they are, and apparently have always been, as favourable for the

deposition of sediment as they were when the tertiary formations were

copiously deposited,—and though they have been upheaved to an amount

quite sufficient to bring up strata from the depths the most fertile

for animal life—can be explained in accordance with the above

proposition. As a deduction, it was also attempted to be shown, first,

that the want of close sequence in the fossils of successive

formations, and of successive stages in the same formation, would

follow from the improbability of the same area continuing slowly to

subside from one whole period to another, or even during a single

entire period; and secondly, that certain epochs having been favourable

at distant points, in the same quarter of the world for the synchronous

accumulation of fossiliferous strata, would follow from movements of

subsidence having apparently, like those of elevation,

contemporaneously affected very large areas.

There is another point which deserves some notice, namely, the analogy

between the upper parts of the Patagonian tertiary formation, as well

as of the upper possibly contemporaneous beds at Chiloe and Concepcion,

with the great gypseous formation of Cordillera; for in both

formations, the rocks, in their fusible nature, in their containing

gypsum, and in many other characters, show a connection, either

intimate or remote, with volcanic action; and as the strata in both

were accumulated during subsidence, it appears at first natural to

connect this sinking movement with a state of high activity in the

neighbouring volcanoes. During the cretaceo-oolitic period this

certainly appears to have been the case at the Puente del Inca, judging

from the number of intercalated lava-streams in the lower 3,000 feet of

strata; but generally, the volcanic orifices seem at this time to have

existed as submarine solfataras, and were certainly quiescent compared

with their state during the accumulation of the porphyritic

conglomerate formation. During the deposition of the tertiary strata we

know that at S. Cruz, deluges of basaltic lava were poured forth; but

as these lie in the upper part of the series, it is possible that the

subsidence may at that time have ceased: at Chiloe, I was unable to

ascertain to what part of the series the pile of lavas belonged. The

Uspallata tuffs and great streams of submarine lavas, were probably

intermediate in age between the cretaceo- oolitic and older tertiary

formations, and we know from the buried trees that there was a great

subsidence during their accumulation; but even in this case, the

subsidence may not have been strictly contemporaneous with the great

volcanic eruptions, for we must believe in at least one intercalated

period of elevation, during which the ground was upraised on which the

now buried trees grew. I have been led to make these remarks, and to

throw some doubt on the strict contemporaneousness of high volcanic

activity and movements of subsidence, from the conviction impressed on

my mind by the study of coral formations, that these two actions do not

generally go on synchronously;—on the contrary, that in volcanic

districts, subsidence ceases as soon as the orifices burst forth into

renewed action, and only recommences when they again have become

dormant. (“The Structure and Distribution of Coral Reefs.”)

At a later period, the Pampean mud, of estuary origin, was deposited

over a wide area,—in one district conformably on the underlying old

tertiary strata, and in another district unconformably on them, after

their upheaval and denudation. During and before the accumulation,

however, of these old tertiary strata, and, therefore, at a very remote

period, sediment, strikingly resembling that of the Pampas, was

deposited; showing during how long a time in this case the same

agencies were at work in the same area. The deposition of the Pampean

estuary mud was accompanied, at least in the southern parts of the

Pampas, by an elevatory movement, so that the M. Hermoso beds probably

were accumulated after the upheaval of those round the S. Ventana; and

those at P. Alta after the upheaval of the M. Hermoso strata; but there

is some reason to suspect that one period of subsidence intervened,

during which mud was deposited over the coarse sand of the Barrancas de

S. Gregorio, and on the higher parts of Banda Oriental. The mammiferous

animals characteristic of this formation, many of which differ as much

from the present inhabitants of South America, as do the eocene mammals

of Europe from the present ones of that quarter of the globe, certainly

co-existed at B. Blanca with twenty species of mollusca, one balanus,

and two corals, all now living in the adjoining sea: this is likewise

the case in Patagonia with the Macrauchenia, which co-existed with

eight shells, still the commonest kinds on that coast. I will not

repeat what I have elsewhere said, on the place of habitation, food,

wide range, and extinction of the numerous gigantic mammifers, which at

this late period inhabited the two Americas.

The nature and grouping of the shells embedded in the old tertiary

formations of Patagonia and Chile show us, that the continent at that

period must have stood only a few fathoms below its present level, and

that afterwards it subsided over a wide area, seven or eight hundred

feet. The manner in which it has since been rebrought up to its actual

level, was described in detail in the First and Second Chapters. It was

there shown that recent shells are found on the shores of the Atlantic,

from Tierra del Fuego northward for a space of at least 1,180 nautical

miles, and at the height of about 100 feet in La Plata, and of 400 feet

in Patagonia. The elevatory movements on this side of the continent

have been slow; and the coast of Patagonia, up to the height in one

part of 950 feet and in another of 1,200 feet, is modelled into eight

great, step-like, gravel-capped plains, extending for hundreds of miles

with the same heights; this fact shows that the periods of denudation

(which, judging from the amount of matter removed, must have been long

continued) and of elevation were synchronous over surprisingly great

lengths of coasts. On the shores of the Pacific, upraised shells of

recent species, generally, though not always, in the same proportional

numbers as in the adjoining sea, have actually been found over a north

and south space of 2,075 miles, and there is reason to believe that

they occur over a space of 2,480 miles. The elevation on this western

side of the continent has not been equable; at Valparaiso, within the

period during which upraised shells have remained undecayed on the

surface, it has been 1,300 feet, whilst at Coquimbo, 200 miles

northward, it has been within this same period only 252 feet. At Lima,

the land has been uplifted at least 80 feet since Indian man inhabited

that district; but the level within historical times apparently has

subsided. At Coquimbo, in a height of 364 feet, the elevation has been

interrupted by five periods of comparative rest. At several places the

land has been lately, or still is, rising both insensibly and by sudden

starts of a few feet during earthquake-shocks; this shows that these

two kinds of upward movement are intimately connected together. For a

space of 775 miles, upraised recent shells are found on the two

opposite sides of the continent; and in the southern half of this

space, it may be safely inferred from the slope of the land up to the

Cordillera, and from the shells found in the central part of Tierra del

Fuego, and high up the River Santa Cruz, that the entire breadth of the

continent has been uplifted. From the general occurrence on both coasts

of successive lines of escarpments, of sand-dunes and marks of erosion,

we must conclude that the elevatory movement has been normally

interrupted by periods, when the land either was stationary, or when it

rose at so slow a rate as not to resist the average denuding power of

the waves, or when it subsided. In the case of the present high

sea-cliffs of Patagonia and in other analogous instances, we have seen

that the difficulty in understanding how strata can be removed at those

depths under the sea, at which the currents and oscillations of the

water are depositing a smooth surface of mud, sand, and sifted pebbles,

leads to the suspicion that the formation or denudation of such cliffs

has been accompanied by a sinking movement.

In South America, everything has taken place on a grand scale, and all

geological phenomena are still in active operation. We know how violent

at the present day the earthquakes are, we have seen how great an area

is now rising, and the plains of tertiary origin are of vast

dimensions; an almost straight line can be drawn from Tierra del Fuego

for 1,600 miles northward, and probably for a much greater distance,

which shall intersect no formation older than the Patagonian deposits;

so equable has been the upheaval of the beds, that throughout this long

line, not a fault in the stratification or abrupt dislocation was

anywhere observable. Looking to the basal, metamorphic, and plutonic

rocks of the continent, the areas formed of them are likewise vast; and

their planes of cleavage and foliation strike over surprisingly great

spaces in uniform directions. The Cordillera, with its pinnacles here

and there rising upwards of twenty thousand feet above the level of the

sea, ranges in an unbroken line from Tierra del Fuego, apparently to

the Arctic circle. This grand range has suffered both the most violent

dislocations, and slow, though grand, upward and downward movements in

mass; I know not whether the spectacle of its immense valleys, with

mountain-masses of once liquified and intrusive rocks now bared and

intersected, or whether the view of those plains, composed of shingle

and sediment hence derived, which stretch to the borders of the

Atlantic Ocean, is best adapted to excite our astonishment at the

amount of wear and tear which these mountains have undergone.

The Cordillera from Tierra del Fuego to Mexico, is penetrated by

volcanic orifices, and those now in action are connected in great

trains. The intimate relation between their recent eruptions and the

slow elevation of the continent in mass, appears to me highly

important, for no explanation of the one phenomenon can be considered

as satisfactory which is not applicable to the other. (On the

Connection of certain Volcanic Phenomena in South America: “Geological

Transactions” volume 5 page 609.) The permanence of the volcanic action

on this chain of mountains is, also, a striking fact; first, we have

the deluges of submarine lavas alternating with the porphyritic

conglomerate strata, then occasionally feldspathic streams and abundant

mineral exhalations during the gypseous or cretaceo- oolitic period:

then the eruptions of the Uspallata range, and at an ancient but

unknown period, when the sea came up to the eastern foot of the

Cordillera, streams of basaltic lava at the foot of the Portillo range;

then the old tertiary eruptions; and lastly, there are here and there

amongst the mountains, much worn and apparently very ancient volcanic

formations without any craters; there are, also, craters quite extinct,

and others in the condition of solfataras, and others occasionally or

habitually in fierce action. Hence it would appear that the Cordillera

has been, probably with some quiescent periods, a source of volcanic

matter from an epoch anterior to our cretaceo-oolitic formation to the

present day; and now the earthquakes, daily recurrent on some part of

the western coast, give little hope that the subterranean energy is

expended.

Recurring to the evidence by which it was shown that some at least of

the parallel ridges, which together compose the Cordillera, were

successively and slowly upthrown at widely different periods; and that

the whole range certainly once, and almost certainly twice, subsided

some thousand feet, and being then brought up by a slow movement in

mass, again, during the old tertiary formations, subsided several

hundred feet, and again was brought up to its present level by a slow

and often interrupted movement; we see how opposed is this complicated

history of changes slowly effected, to the views of those geologists

who believe that this great mountain-chain was formed in late times by

a single blow. I have endeavoured elsewhere to show, that the

excessively disturbed condition of the strata in the Cordillera, so far

from indicating single periods of extreme violence, presents

insuperable difficulties, except on the admission that the masses of

once liquified rocks of the axes were repeatedly injected with

intervals sufficiently long for their successive cooling and

consolidation. (“Geological Transactions” volume 5 page 626.) Finally,

if we look to the analogies drawn from the changes now in progress in

the earth’s crust, whether to the manner in which volcanic matter is

erupted, or to the manner in which the land is historically known to

have risen and sunk: or again, if we look to the vast amount of

denudation which every part of the Cordillera has obviously suffered,

the changes through which it has been brought into its present

condition, will appear neither to have been too slowly effected, nor to

have been too complicated.

NOTE.

As, both in France and England, translations of a passage in Professor

Ehrenberg’s Memoir, often referred to in the Fourth Chapter of this

volume, have appeared, implying that Professor Ehrenberg believes, from

the character of the infusoria, that the Pampean formation was

deposited by a sea-debacle rushing over the land, I may state, on the

authority of a letter to me, that these translations are incorrect. The

following is the passage in question:—

“Durch Beachtung der mikroscopischen Formen hat sich nun feststellen

lassen, das die Mastodonten-Lager am La Plata und die Knochen-Lager am

Monte Hermoso, who wie die der Riesen-Gurtelthiere in den Dunenhugeln

bei Bahia Blanca, beides in Patagonien, unveranderte brakische

Susswasserbildungen sind, die einst wohl sammtlich zum obersten

Fluthgebiethe des Meeres im tieferen Festlande

gehorten.”—“Monatsberichten der konigl. Akad. etc.” zu Berlin vom April

1845.

INDEX.

Abich, on a new variety of feldspar.

Abrolhos islands.

Absence of recent formations on the S. American coasts.

Aguerros on elevation of Imperial.

Albite, constituent mineral in andesite. —in rocks of Tierra del Fuego.

—in porphyries. —crystals of, with orthite.

Alison, Mr., on elevation of Valparaiso.

Alumina, sulphate of.

Ammonites from Concepcion.

Amolanas, Las.

Amygdaloid, curious varieties of.

Amygdaloids of the Uspallata range. —of Copiapo.

Andesite of Chile. —in the valley of Maypu. —of the Cumbre pass. —of

the Uspallata range. —of Los Hornos. —of Copiapo.

Anhydrite, concretions of.

Araucaria, silicified wood of. Arica, elevation of.

Arqueros, mines of.

Ascension, gypsum deposited on. —laminated volcanic rocks of.

Augite in fragments, in gneiss. —with albite, in lava.

Austin, Mr. R.A.C., on bent cleavage lamina.

Austin, Captain, on sea-bottom.

Australia, foliated rocks of.

Azara labiata, beds of, at San Pedro.

Baculites vagina.

Bahia Blanca, elevation of. —formations near. —character of living

shells of.

Bahia (Brazil), elevation near. —crystalline rocks of.

Ballard, M., on the precipitation of sulphate of soda.

Banda Oriental, tertiary formations of. —crystalline rocks of.

Barnacles above sea-level. —adhering to upraised shells.

Basalt of S. Cruz. —streams of, in the Portillo range. —in the

Uspallata range.

Basin chains of Chile.

Beagle Channel.

Beaumont, Elie de, on inclination of lava-streams. —on viscid

quartz-rocks.

Beech-tree, leaves of fossil.

Beechey, Captain, on sea-bottom.

Belcher, Lieutenant, on elevated shells from Concepcion.

Bella Vista, plain of.

Benza, Dr., on decomposed granite.

Bettington, Mr., on quadrupeds transported by rivers.

Blake, Mr., on the decay of elevated shells near Iquique. —on nitrate

of soda.

Bole.

Bollaert, Mr., on mines of Iquique.

Bones, silicified. —fossil, fresh condition of.

Bottom of sea off Patagonia.

Bougainville, on elevation of the Falkland islands.

Boulder formation of S. Cruz. —of Falkland islands. —anterior to

certain extinct quadrupeds. —of Tierra del Fuego.

Boulders in the Cordillera. —transported by earthquake-waves. —in

fine-grained tertiary deposits.

Brande, Mr., on a mineral spring.

Bravais, M., on elevation of Scandinavia.

Brazil, elevation of. —crystalline rocks of.

Broderip, Mr., on elevated shells from Concepcion.

Brown, Mr. R., on silicified wood of Uspallata range.

Brown, on silicified wood.

Bucalema, elevated shells near.

Buch, Von, on cleavage. —on cretaceous fossils of the Cordillera. —on

the sulphureous volcanoes of Java.

Buenos Ayres.

Burchell, Mr., on elevated shells of Brazil.

Byron, on elevated shells.

Cachapual, boulders in valley of.

Caldcleugh, Mr., on elevation of Coquimbo. —on rocks of the Portillo

range.

Callao, elevation near. —old town of.

Cape of Good Hope, metamorphic rocks of.

Carcharias megalodon.

Carpenter, Dr., on microscopic organisms.

Castro (Chiloe), beds near.

Cauquenes Baths, boulders near. —pebbles in porphyry near. —volcanic

formation near. —stratification near.

Caves above sea-level.

Cervus pumilus, fossil-horns of.

Chevalier, M., on elevation near Lima.

Chile, structure of country between the Cordillera and the Pacific.

—tertiary formations of. —crystalline rocks in. —central, geology of.

—northern, geology of.

Chiloe, gravel on coast. —elevation of. —tertiary formation of.

—crystalline rocks of.

Chlorite-schist, near M. Video.

Chonos archipelago, tertiary formations of. —crystalline rocks of.

Chupat, Rio, scoriae transported by.

Claro, Rio, fossiliferous beds of.

Clay-shale of Los Hornos.

Clay-slate, formation of, Tierra del Fuego. —of Concepcion.

—feldspathic, of Chile. — —of the Uspallata range. —black siliceous,

band of, in porphyritic formations of Chile.

Claystone porphyry, formation of, in Chile. —origin of. —eruptive

sources of.

Cleavage, definition of. —at Bahia. —Rio de Janeiro. —Maldonado. —Monte

Video. —S. Guitru-gueyu. —Falkland I. —Tierra del Fuego. —Chonos I.

—Chiloe. —Concepcion. —Chile. —discussion on.

Cleavage-laminae superficially bent.

Cliffs, formation of.

Climate, late changes in. —of Chile during tertiary period.

Coal of Concepcion. —S. Lorenzo.

Coast-denudation of St. Helena.

Cobija, elevation of.

Colombia, cretaceous formation of.

Colonia del Sacramiento, elevation of. —Pampean formation near

Colorado, Rio, gravel of. —sand-dunes of. —Pampean formation near.

Combarbala.

Concepcion, elevation of. —deposits of. —crystalline rocks of.

Conchalee, gravel-terraces of.

Concretions of gypsum, at Iquique. —in sandstone at S. Cruz. —in

tufaceous tuff of Chiloe. —in gneiss. —in claystone-porphyry at Port

Desire. —in gneiss at Valparaiso. —in metamorphic rocks. —of anhydrite.

—relations of, to veins.

Conglomerate claystone of Chile. —of Tenuyan. —of the Cumbre Pass. —of

Rio Claro. —of Copiapo.

Cook, Captain, on form of sea-bottom.

Copiapo, elevation of. —tertiary formations of. —secondary formations

of.

Copper, sulphate of. —native, at Arqueros. —mines of, at Panuncillo.

—veins, distribution of.

Coquimbo, elevation and terraces of. —tertiary formations of.

—secondary formations of.

Corallines living on pebbles.

Cordillera, valleys bordered by gravel fringes. —basal strata of.

—fossils of. —elevation of. —gypseous formations of.

—claystone-porphyries of. —andesitic rocks of. —volcanoes of.

Coste, M., on elevation of Lemus.

Coy inlet, tertiary formation of.

Crassatella Lyellii.

Cruickshanks, Mr., on elevation near Lima.

Crystals of feldspar, gradual formation of, at Port Desire.

Cumbre, Pass of, in Cordillera.

Cuming, Mr., on habits of the Mesodesma. —on range of living shells on

west coast.

Dana, Mr., on foliated rocks. —on amygdaloids.

Darwin, Mount.

D’Aubuisson, on concretions. —on foliated rocks. Decay, gradual, of

upraised shells.

Decomposition of granite rocks.

De la Beche, Sir H., his theoretical researches in geology. —on the

action of salt on calcareous rocks. —on bent cleavage-laminae.

Denudation on coast of Patagonia. —great powers of. —of the Portillo

range.

Deposits, saline.

Despoblado, valley of.

Detritus, nature of, in Cordillera.

Devonshire, bent cleavage in.

Dikes, in gneiss of Brazil. —near Rio de Janeiro. —pseudo, at Port

Desire. —in Tierra del Fuego. —in Chonos archipelago, containing

quartz. —near Concepcion, with quartz. —granitic-porphyritic, at

Valparaiso. —rarely vesicular in Cordillera. —absent in the central

ridges of the Portillo pass. —of the Portillo range, with grains of

quartz. —intersecting each other often. —numerous at Copiapo.

Domeyko, M., on the silver mines of Coquimbo. on the fossils of

Coquimbo.

D’Orbigny, M. A., on upraised shells of Monte Video. —on elevated

shells at St. Pedro. —on elevated shells near B. Ayres. —on elevation

of S. Blas. —on the sudden elevation of La Plata. —on elevated shells

near Cobija. —on elevated shells near Arica. —on the climate of Peru.

—on salt deposits of Cobija. —on crystals of gypsum in salt-lakes. —on

absence of gypsum in the Pampean formation. —on fossil remains from

Bahia Blanca. —on fossil remains from the banks of the Parana. —on the

geology of St. Fe. —on the age of Pampean formation. —on the Mastodon

Andium. —on the geology of the Rio Negro. —on the character of the

Patagonian fossils. —on fossils from Concepcion. — —from Coquimbo. —

—from Payta. —on fossil tertiary shells of Chile. —on cretaceous

fossils of Tierra del Fuego. — —from the Cordillera of Chile.

Earth, marine origin of.

Earthenware, fossil.

Earthquake, effect of, at S. Maria. —elevation during, at Lemus. —of

1822, at Valparaiso. —effects of, in shattering surface. —fissures made

by. —probable effects on cleavage.

Earthquakes in Pampas.

Earthquake-waves, power of, in throwing up shells. —effects of, near

Lima. —power of, in transporting boulders.

Edmonston, Mr., on depths at which shells live at Valparaiso.

Ehrenberg, Professor, on infusoria in the Pampean formation. —on

infusoria in the Patagonian formation.

Elevation of La Plata. —Brazil. —Bahia Blanca. —San Blas. —Patagonia.

—Tierra del Fuego. —Falkland islands. —Pampas. —Chonos archipelago.

—Chiloe. —Chile. —Valparaiso. —Coquimbo. —Guasco. —Iquique. —Cobija.

—Lima. —sudden, at S. Maria. — —at Lemus. —insensible, at Chiloe. — —at

Valparaiso. — —at Coquimbo. —axes of, at Chiloe. — —at P. Rumena. —at

Concepcion. —unfavourable for the accumulation of permanent deposits.

—lines of, parallel to cleavage and foliation. —lines of, oblique to

foliation. —areas of, causing lines of elevation and cleavage. —lines

of, in the Cordillera. —slow, in the Portillo range. —two periods of,

in Cordillera of Central Chile. —of the Uspallata range. —two periods

of, in Cumbre Pass. —horizontal, in the Cordillera of Copiapo. —axes

of, coincident with volcanic orifices. —of the Cordillera, summary on.

Elliott, Captain, on human remains.

Ensenada, elevated shells of.

Entre Rios, geology of.

Equus curvidens.

Epidote in Tierra del Fuego. —in gneiss. —frequent in Chile. —in the

Uspallata range. —in porphyry of Coquimbo.

Erman, M., on andesite. Escarpments, recent, of Patagonia.

Extinction of fossil mammifers.

Falkland islands, elevation of. —pebbles on coast. —geology of.

Falkner, on saline incrustations.

Faults, great, in Cordillera.

Feldspar, earthy, metamorphosis of, at Port Desire. —albitic. —crystals

of, with albite. —orthitic, in conglomerate of Tenuyan. —in granite of

Portillo range. —in porphyries in the Cumbre Pass.

Feuillee on sea-level at Coquimbo.

Fissures, relations of, to concretions. —upfilled, at Port Desire. —in

clay-slate.

Fitton, Dr., on the geology of Tierra del Fuego.

Fitzroy, Captain, on the elevation of the Falkland islands. —on the

elevation of Concepcion.

Foliation, definition of. —of rocks at Bahia. —Rio de Janeiro.

—Maldonado. —Monte Video. —S. Guitru-gueyu. —Falkland I. —Tierra del

Fuego. —Chonos archipelago. —Chiloe. —Concepcion. —Chile. —discussion

on.

Forbes, Professor E., on cretaceous fossils of Concepcion. —on

cretaceous fossils and subsidence in Cumbre Pass. —on fossils from

Guasco. — —from Coquimbo. — —from Copiapo. —on depths at which shells

live.

Formation, Pampean. — —area of. — —estuary origin. —tertiary of Entre

Rios. —of Banda Oriental. —volcanic, in Banda Oriental. —of Patagonia.

—summary on. —tertiary of Tierra del Fuego. — —of the Chonos

archipelago. — —of Chiloe. — —of Chile. — —of Concepcion. — —of

Navidad. — —of Coquimbo. — —of Peru. — —subsidence during. —volcanic,

of Tres Montes. — —of Chiloe. — —old, near Maldonado. — —with laminar

structure. — —ancient, in Tierra del Fuego. —recent, absent on S.

American coast. —metamorphic, of claystone-porphyry of Patagonia.

—foliation of. —plutonic, with laminar structure. —palaeozoic, of the

Falkland I. —claystone, at Concepcion. —Jurassic, of Cordillera.

—Neocomian, of the Portillo Pass. —volcanic, of Cumbre Pass. —gypseous,

of Los Hornos. — —of Coquimbo. — —of Guasco. — —of Copiapo. — —of

Iquique. —cretaceo-oolitic, of Coquimbo. — —of Guasco. — —of Copiapo. —

—of Iquique.

Fossils, Neocomian, of Portillo Pass. — —of Cumbre Pass. —secondary, of

Coquimbo. — —of Guasco. — —of Copiapo. — —of Iquique. —palaeozoic, from

the Falklands.

Fragments of hornblende-rock in gneiss. —of gneiss in gneiss.

Freyer, Lieutenant, on elevated shells of Arica.

Frezier on sea-level at Coquimbo.

Galapagos archipelago, pseudo-dikes of.

Gallegos, Port, tertiary formation of.

Garnets in gneiss. —in mica-slate. —at Panuncillo.

Gardichaud, M., on granites of Brazil.

Gay, M., on elevated shells. —on boulders in the Cordillera. —on

fossils from Cordillera of Coquimbo.

Gill, Mr., on brickwork transported by an earthquake-wave.

Gillies, Dr., on heights in the Cordillera. —on extension of the

Portillo range.

Glen Roy, parallel roads of. —sloping terraces of.

Gneiss, near Bahia. —of Rio de Janeiro. —decomposition of.

Gold, distribution of.

Gorodona, formations near. Granite, axis of oblique, to foliation.

—andesitic. —of Portillo range. —veins of, quartzose. —pebble of, in

porphyritic conglomerate. —conglomerate.

Grauwacke of Uspallata range.

Gravel at bottom of sea. —formation of, in Patagonia. —means of

transportation of. —strata of, inclined.

Gravel-terraces in Cordillera.

Greenough, Mr., on quartz veins.

Greenstone, resulting from metamorphose hornblende-rock. —of Tierra del

Fuego. —on the summit of the Campana of Quillota. —porphyry. —relation

of, to clay-slate.

Gryphaea orientalis.

Guasco, elevation of. —secondary formation of.

Guitru-gueyu, Sierra.

Guyana, gneissic rocks of.

Gypsum, nodules of, in gravel at Rio Negro. —deposited from sea-water.

—deposits of, at Iquique. —crystals of, in salt lakes. —in Pampean

formation. —in tertiary formation of Patagonia. —great formation of, in

the Portillo Pass. — —in the Cumbre Pass. — —near Los Hornos. — —at

Coquimbo. — —at Copiapo. — —near Iquique. —of San Lorenzo.

Hall, Captain, on terraces at Coquimbo.

Hamilton, Mr., on elevation near Tacna.

Harlan, Dr., on human remains.

Hayes, Mr. A., on nitrate of soda.

Henslow, Professor, on concretions.

Herbert, Captain, on valleys in the Himalaya.

Herradura Bay, elevated shells of. —tertiary formations of.

Himalaya, valleys in.

Hippurites Chilensis.

Hitchcock, Professor, on dikes.

Honestones, pseudo, of Coquimbo. —of Copiapo.

Hooker, Dr. J.D., on fossil beech-leaves.

Hopkins, Mr., on axes of elevation oblique to foliation. —on origin of

lines of elevation.

Hornblende-rock, fragments of, in gneiss.

Hornblende-schist, near M. Video.

Hornos, Los, section near.

Hornstone, dike of.

Horse, fossil tooth of.

Huafo island. —subsidence at.

Huantajaya, mines of.

Humboldt, on saline incrustations. —on foliations of gneiss. —on

concretions in gneiss.

Icebergs, action on cleavage.

Illapel, section near.

Imperial, beds of shells near.

Incrustations, saline.

Infusoria in Pampean formation. —in Patagonian formation.

Iodine, salts of.

Iquique, elevation of. —saliferous deposits of. —cretaceo-oolitic

formation of.

Iron, oxide of, in lavas. —in sedimentary beds. —tendency in, to

produce hollow concretions. —sulphate of.

Isabelle, M., on volcanic rocks of Banda Oriental.

Joints in clay-slate.

Jukes, Mr., on cleavage in Newfoundland.

Kamtschatka, andesite of.

Kane, Dr., on the production of carbonate of soda.

King George’s sound, calcareous beds of.

Lakes, origin of. —fresh-water, near salt lakes.

Lava, basaltic, of S. Cruz. —claystone-porphyry, at Chiloe. — —ancient

submarine. —basaltic, of the Portillo range. —feldspathic, of the

Cumbre Pass. —submarine, of the Uspallata range. —basaltic, of the

Uspallata range. —submarine, of Coquimbo. —of Copiapo.

Lemus island.

Lemuy islet.

Lignite of Chiloe. —of Concepcion.

Lima, elevation of.

Lime, muriate of.

Limestone of Cumbre Pass. —of Coquimbo. —of Copiapo.

Lund and Clausen on remains of caves in Brazil.

Lund, M., on granites of Brazil.

Lyell, M., on upraised shells retaining their colours. —on terraces at

Coquimbo. —on elevation near Lima. —on fossil horse’s tooth. —on the

boulder-formation being anterior to the extinction of North American

mammifers. —on quadrupeds washed down by floods. —on age of American

fossil mammifers. —on changes of climate. —on denudation. —on

foliation.

MacCulloch, Dr., on concretions. —on beds of marble.

Maclaren, Mr., letter to, on coral-formations.

Macrauchenia Patachonica.

Madeira, subsidence of.

Magellan, Strait, elevation near, of.

Magnesia, sulphate of, in veins.

Malcolmson, Dr., on trees carried out to sea.

Maldonado, elevation of. —Pampean formation of. —crystalline rocks of.

Mammalia, fossil, of Bahia Blanca. — —near St. Fe. — —of Banda

Oriental. — —of St. Julian. — —at Port Gallegos. —washed down by

floods. —number of remains of, and range of, in Pampas.

Man, skeletons of (Brazil). —remains of, near Lima. —Indian, antiquity

of.

Marble, beds of.

Maricongo, ravine of.

Marsden, on elevation of Sumatra.

Mastodon Andium, remains of. —range of.

Maypu, Rio, mouth of, with upraised shells. —gravel fringes of.

—debouchement from the Cordillera.

Megalonyx, range of.

Megatherium, range of.

Miers, Mr., on elevated shells. —on the height of the Uspallata plain.

Minas, Las.

Mocha Island, elevation of. —tertiary form of. —subsidence at.

Molina, on a great flood.

Monte Hermoso, elevation of. —fossils of.

Monte Video, elevation of. —Pampean formation of. —crystalline rocks

of.

Morris and Sharpe, Messrs., on the palaeozoic fossils of the Falklands.

Mud, Pampean. —long deposited on the same area.

Murchison, Sir R., on cleavage. —on waves transporting gravel. —on

origin of salt formations. —on the relations of metalliferous veins and

intrusive rocks. —on the absence of granite in the Ural.

Nautilus d’Orbignyanus.

Navidad, tertiary formations of, subsidence of.

Negro, Rio, pumice of pebbles of. —gravel of. —salt lakes of. —tertiary

strata of.

North America, fossil remains of.

North Wales, sloping terraces absent in. —bent cleavage of.

Neuvo Gulf, plains of. —tertiary formation of.

Owen, Professor, on fossil mammiferous remains.

Palmer, Mr., on transportation of gravel.

Pampas, elevation of. —earthquakes of. —formation of. —localities in

which fossil mammifers have been found.

Panuncillo, mines of.

Parana, Rio, on saline incrustations. —Pampean formations near. —on the

S. Tandil.

Parish, Sir W., on elevated shells near Buenos Ayres. —on earthquakes

in the Pampas. —on fresh-water near salt lakes. —on origin of Pampean

formation.

Patagonia, elevation and plains of. —denudation of. —gravel-formation

of. —sea-cliffs of. —subsidence during tertiary period. —crystalline

rocks of.

Payta, tertiary formations of.

Pebbles of pumice. —decrease in size on the coast of Patagonia. —means

of transportation. —encrusted with living corallines. —distribution of,

at the eastern foot of Cordillera. —dispersal of, in the Pampas. —zoned

with colour.

Pentland, Mr., on heights in the Cordillera. —on fossils of the

Cordillera.

Pernambuco.

Peru, tertiary formations of.

Peuquenes, Pass of, in the Cordillera. —ridge of.

Pholas, elevated shells of.

Pitchstone of Chiloe. —of Port Desire. —near Cauquenes. —layers of, in

the Uspallata range. —of Los Hornos. —of Coquimbo.

Plains of Patagonia. —of Chiloe. —of Chile. —of Uspallata. —on eastern

foot of Cordillera. —of Iquique.

Plata, La, elevation of. —tertiary formation of. —crystalline rocks of.

Playfair, Professor, on the transportation of gravel.

Pluclaro, axis of.

Pondicherry, fossils of.

Porcelain rocks of Port Desire. —of the Uspallata range.

Porphyry, pebbles of, strewed over Patagonia.

Porphyry, claystone, of Chiloe, — —of Patagonia. — —of Chile.

—greenstone, of Chile. —doubly columnar. —claystone, rare, on the

eastern side of the Portillo Pass. —brick-red and orthitic, of Cumbre

Pass. —intrusive, repeatedly injected. —claystone of the Uspallata

range. — —of Copiapo. — —eruptive sources of.

Port Desire, elevation and plains of. —tertiary formation of.

—porphyries of.

Portillo Pass in the Cordillera.

Portillo chain. —compared with that of the Uspallata.

Prefil or sea-wall of Valparaiso.

Puente del Inca, section of.

Pumice, pebbles of. —conglomerate of R. Negro. —hills of, in the

Cordillera.

Punta Alta, elevation of. —beds of.

Quartz-rock of the S. Ventana. —C. Blanco. —Falkland islands. —Portillo

range. —viscidity of. —veins of, near Monte Video. — —in dike of

greenstone. —grains of, in mica slate. — —in dikes. —veins of,

relations to cleavage.

Quillota, Campana of.

Quintero, elevation of.

Quiriquina, elevation of. —deposits of.

Rancagua, plain of.

Rapel, R. elevation near.

Reeks, Mr. T., his analysis of decomposed shells. —his analysis of

salts.

Remains, human.

Rio de Janeiro, elevation near. —crystalline rocks of.

Rivers, small power of transporting pebbles. —small power of, in

forming valleys. —drainage of, in the Cordillera.

Roads, parallel, of Glen Roy.

Rocks, volcanic, of Banda Oriental. —Tres Montes. —Chiloe. —Tierra del

Fuego. —with laminar structure.

Rodents, fossil, remains of.

Rogers, Professor, address to Association of American Geologists.

Rose, Professor G., on sulphate of iron at Copiapo.

S. Blas, elevation of.

S. Cruz, elevation and plains of. —valley of. —nature of gravel in

valley of. —boulder formation of. —tertiary formation of. —subsidence

at.

S. Fe Bajada, formations of.

S. George’s bay, plains of.

S. Helena island, sea-cliffs, and subsidence of.

S. Josef, elevation of. —tertiary formation of.

S. Juan, elevation near.

S. Julian, elevation and plains of. —salt lake of. —earthy deposit with

mammiferous remains. —tertiary formations of. —subsidence at.

S. Lorenzo, elevation of. —old salt formation of.

S. Mary, island of, elevation of.

S. Pedro, elevation of.

Salado, R., elevated shells of. —Pampean formation of.

Salines.

Salt, with upraised shell. —lakes of. —purity of, in salt lakes.

—deliquescent, necessary for the preservation of meat. —ancient

formation of, at Iquique. — —at S. Lorenzo. —strata of, origin of.

Salts, superficial deposits of.

Sand-dunes of the Uruguay. —of the Pampas. —near Bahia Blanca. —of the

Colorado. —of S. Cruz. —of Arica.

Sarmiento, Mount.

Schmidtmeyer on auriferous detritus.

Schomburghk, Sir R., on sea-bottom. —on the rocks of Guyana.

Scotland, sloping terraces of.

Sea, nature of bottom of, off Patagonia. —power of, in forming valleys.

Sea cliffs, formation of.

Seale, Mr., model of St. Helena.

Sebastian Bay, tertiary formation of.

Sedgwick, Professor, on cleavage.

Serpentine of Copiapo.

Serpulae, on upraised rocks.

Shale-rock, of the Portillo Pass. —of Copiapo.

Shells, upraised state of, in Patagonia. —elevated, too small for human

food. —transported far inland, for food. —upraised, proportional

numbers varying. — —gradual decay of. — —absent on high plains of

Chile. — —near Bahia Blanca. —preserved in concretions. —living and

fossil range of, on west coast. —living, different on the east and west

coast.

Shingle of Patagonia.

Siau, M., on sea-bottom.

Silver mines of Arqueros. —of Chanuncillo. —of Iquique. —distribution

of.

Slip, great, at S. Cruz.

Smith, Mr., of Jordan Hill, on upraised shells retaining their colours.

—on Madeira. —on elevated seaweed. —on inclined gravel beds.

Soda, nitrate of. —sulphate of, near Bahia Blanca. —carbonate of.

Soundings off Patagonia. —in Tierra del Fuego.

Spirifers.

Spix and Martius on Brazil. Sprengel on the production of carbonate of

soda.

Springs, mineral, in the Cumbre Pass.

Stratification of sandstone in metamorphic rocks. —of clay-slate in

Tierra del Fuego. —of the Cordillera of Central Chile. —little

disturbed in Cumbre Pass. —disturbance of, near Copiapo.

Streams of lava at S. Cruz, inclination of. —in the Portillo range.

String of cotton with fossil-shells.

Struthiolaria ornata.

Studer, M., on metamorphic rocks.

Subsidence during formation of sea-cliffs. —near Lima. —probable,

during Pampean formation. —necessary for the accumulation of permanent

deposits. —during the tertiary formations of Chile and Patagonia.

—probable during the Neocomian formation of the Portillo Pass.

—probable during the formation of conglomerate of Tenuyan. —during the

Neocomian formation of the Cumbre Pass. —of the Uspallata range.

—great, at Copiapo. — —during the formation of the Cordillera.

Sulphur, volcanic exhalations of.

Sumatra, promontories of.

A Summary on the recent elevatory movements. —on the Pampean formation.

—on the tertiary formations of Patagonia and Chile. —on the Chilean

Cordillera. —on the cretaceo-oolitic formation. —on the subsidences of

the Cordillera. —on the elevation of the Cordillera.

Tacna, elevation of.

Tampico, elevated shells near.

Tandil, crystalline rocks of.

Tapalguen, Pampean formation of. —crystalline rocks of.

Taylor, Mr., on copper veins of Cuba.

Temperature of Chile during the tertiary period.

Tension, lines of, origin of, axes of elevation and of cleavage.

Tenuy Point, singular section of.

Tenuyan, valley of.

Terraces of the valley of S. Cruz. —of equable heights throughout

Patagonia. —of Patagonia, formation of. —of Chiloe. —at Conchalee. —of

Coquimbo. —not horizontal at Coquimbo. —of Guasco. —of S. Lorenzo. —of

gravel within the Cordillera.

Theories on the origin of the Pampean formation.

Tierra Amarilla.

Tierra del Fuego, form of sea-bottom. —tertiary formations of.

—clay-slate formation of. —cretaceous formation of. —crystalline rocks

of. —cleavage of clay-slate.

Tosca rock.

Trachyte of Chiloe. —of Port Desire. —in the Cordillera.

Traditions of promontories having been islands. —on changes of level

near Lima.

Trees buried in plain of Iquique. —silicified, vertical, of the

Uspallata range.

Tres Montes, elevation of. —volcanic rocks of.

Trigonocelia insolita.

Tristan Arroyo, elevated shells of.

Tschudi, Mr., on subsidence near Lima.

Tuff, calcareous, at Coquimbo. —on basin-plain near St. Jago.

—structure of, in Pampas. —origin of, in Pampas. —pumiceous, of R.

Negro. —Nuevo Gulf. —Port Desire. —S. Cruz. —Patagonia, summary on

Chiloe. —formation of, in Portillo chain. —great deposit of, at

Copiapo.

Tuffs, volcanic, metamorphic, of Uspallata. —of Coquimbo.

Ulloa, on rain in Peru. —on elevation near Lima.

Uruguay, Rio, elevation of country near.

Uspallata, plain of. —pass of. —range of. —concluding remarks on.

Valdivia, tertiary beds of. —mica-slate of.

Valley of S. Cruz, structure of. —Coquimbo. —Guasco, structure of.

—Copiapo, structure of. —S. Cruz, tertiary formations of. —Coquimbo,

geology of. —Guasco, secondary formations of. —Copiapo, secondary

formations of. —Despoblado.

Valleys in the Cordillera bordered by gravel fringes. —formation of.

—in the Cordillera.

Valparaiso, elevation of. —gneiss of.

Vein of quartz near Monte Video. —in mica-slate. —relations of, to

cleavage. —in a trap dike. —of granite, quartzose. —remarkable, in

gneiss, near Valparaiso.

Veins, relations of, to concretions. —metalliferous, of the Uspallata

range. —metalliferous, discussion on.

Venezuela, gneissic rocks of.

Ventana, Sierra, Pampean formation near. —quartz-rock of.

Villa Vincencio Pass.

Volcan, Rio, mouth of. —fossils of.

Volcanoes of the Cordillera. —absent, except near bodies of water.

—ancient submarine, in Cordillera. —action of, in relation to changes

of level. —long action of, in the Cordillera.

Wafer on elevated shells.

Waves caused by earthquakes, power of, in transporting boulders. —power

of, in throwing up shells.

Weaver, Mr., on elevated shells.

White, Martin., on sea-bottom.

Wood, silicified, of Entre Rios. —S. Cruz. —Chiloe. —Uspallata range.

—Los Hornos. —Copiapo.

Yeso, Rio, and plain of.

Ypun Island, tertiary formation of.

Zeagonite.