Chapter 42

Section from Illapel to Combarbala; gypseous formation with silicified wood.—Panuncillo.—Coquimbo; mines of Arqueros; section up valley; fossils.—Guasco, fossils of.—Copiapo, section up valley; Las Amolanas, silicified wood.—Conglomerates, nature of former land, fossils, thickness of strata, great subsidence.—Valley of Despoblado, fossils, tufaceous deposit, complicated dislocations of.—Relations between ancient orifices of eruption and subsequent axes of injection.—Iquique, Peru, fossils of, salt-deposits.—Metalliferous veins.—Summary on the porphyritic conglomerate and gypseous formations.—Great subsidence with partial elevations during the cretaceo-oolitic period.—On the elevation and structure of the Cordillera.—Recapitulation on the tertiary series.—Relation between movements of subsidence and volcanic action.—Pampean formation.—Recent elevatory movements. Long-continued volcanic action in the Cordillera.—Conclusion.

_Valparaiso to Coquimbo._ I have already described the general nature of the rocks in the low country north of Valparaiso, consisting of granites, syenites, greenstones, and altered feldspathic clay-slate. Near Coquimbo there is much hornblendic rock and various dusky-coloured porphyries. I will describe only one section in this district, namely, from near Illapel in a N.E. line to the mines of Los Hornos, and thence in a north by east direction to Combarbala, at the foot of the main Cordillera.

Near Illapel, after passing for some distance over granite, andesite, and andesitic porphyry, we come to a greenish stratified feldspathic rock, which I believe is altered clay-slate, conformably capped by porphyries and porphyritic conglomerate of great thickness, dipping at an average angle of 20° to N.E. by N. The uppermost beds consist of conglomerates and sandstone only a little metamorphosed, and conformably covered by a gypseous formation of very great thickness, but much denuded. This gypseous formation, where first met with, lies in a broad valley or basin, a little southward of the mines of Los Hornos: the lower half alone contains gypsum, not in great masses as in the Cordillera, but in innumerable thin layers, seldom more than an inch or two in thickness. The gypsum is either opaque or transparent, and is associated with carbonate of lime. The layers alternate with numerous varying ones of a calcareous clay-shale (with strong aluminous odour, adhering to the tongue, easily fusible into a pale green glass), more or less indurated, either earthy and cream-coloured, or greenish and hard. The more indurated varieties have a compact, homogeneous, almost crystalline fracture, and contain granules of crystallised oxide of iron. Some of the varieties almost resemble honestones. There is also a little black, hardly fusible, siliceo-calcareous clay-slate, like some of the varieties alternating with gypsum on the Peuquenes range.

The upper half of this gypseous formation is mainly formed of the same calcareous clay-shale rock, but without any gypsum, and varying extremely in nature: it passes from a soft, coarse, earthy, ferruginous state, including particles of quartz, into compact claystones with crystallised oxide of iron,—into porcellanic layers, alternating with seams of calcareous matter,—and into green porcelain-jasper, excessively hard, but easily fusible. Strata of this nature alternate with much black and brown siliceo-calcareous slate, remarkable from the wonderful number of huge embedded logs of silicified wood. This wood, according to Mr. R. Brown, is (judging from several specimens) all coniferous. Some of the layers of the black siliceous slate contained irregular angular fragments of imperfect pitchstone, which I believe, as in the Uspallata range, has originated in a metamorphic process. There was one bed of a marly tufaceous nature, and of little specific gravity. Veins of agate and calcareous spar are numerous. The whole of this gypseous formation, especially the upper half, has been injected, metamorphosed, and locally contorted by numerous hillocks of intrusive porphyries crowded together in an extraordinary manner. These hillocks consist of purple claystone and of various other porphyries, and of much white feldspathic greenstone passing into andesite; this latter variety included in one case crystals of orthitic and albitic feldspar touching each other, and others of hornblende, chlorite, and epidote. The strata surrounding these intrusive hillocks at the mines of Los Hornos, are intersected by many veins of copper-pyrites, associated with much micaceous iron-ore, and by some of gold: in the neighbourhood of these veins the rocks are blackened and much altered. The gypsum near the intrusive masses is always opaque. One of these hillocks of porphyry was capped by some stratified porphyritic conglomerate, which must have been brought up from below, through the whole immense thickness of the overlying gypseous formation. The lower beds of the gypseous formation resemble the corresponding and probably contemporaneous strata of the main Cordillera; whilst the upper beds in several respects resemble those of the Uspallata chain, and possibly may be contemporaneous with them; for I have endeavoured to show that the Uspallata beds were accumulated subsequently to the gypseous or Neocomian formations of the Cordillera.

This pile of strata dips at an angle of about 20 degrees to N.E. by N., close up to the foot of the Cuesta de Los Hornos, a crooked range of mountains formed of intrusive rocks of the same nature with the above described hillocks. Only in one or two places, on this south-eastern side of the range, I noticed a narrow fringe of the upper gypseous strata brushed up and inclined south-eastward from it. On its north-eastern flank, and likewise on a few of the summits, the stratified porphyritic conglomerate is inclined N.E.: so that, if we disregard the very narrow anticlinal fringe of gypseous strata at its S.E. foot, this range forms a second uniclinal axis of elevation. Proceeding in a north-by-east direction to the village of Combarbala, we come to a third escarpment of the porphyritic conglomerate, dipping eastwards, and forming the outer range of the main Cordillera. The lower beds were here more jaspery than usual, and they included some white cherty strata and red sandstones, alternating with purple claystone porphyry. Higher up in the Cordillera there appeared to be a line of andesitic rocks; and beyond them, a fourth escarpment of the porphyritic conglomerate, again dipping eastwards or inwards. The overlying gypseous strata, if they ever existed here, have been entirely removed.

_Copper mines of Panuncillo._—From Combarbala to Coquimbo, I traversed the country in a zigzag direction, crossing and recrossing the porphyritic conglomerate and finding in the granitic districts an unusual number of mountain-masses composed of various intrusive, porphyritic rocks, many of them andesitic. One common variety was greenish-black, with large crystals of blackish albite. At Panuncillo a short N.N.W. and S.S.E. ridge, with a nucleus formed of greenstone and of a slate-coloured porphyry including crystals of glassy feldspar, deserves notice, from the very singular nature of the almost vertical strata composing it. These consist chiefly of a finer and coarser granular mixture, not very compact, of white carbonate of lime, of protoxide of iron and of yellowish garnets (ascertained by Professor Miller), each grain being an almost perfect crystal. Some of the varieties consist exclusively of granules of the calcareous spar; and some contain grains of copper ore, and, I believe, of quartz. These strata alternate with a bluish, compact, fusible, feldspathic rock. Much of the above granular mixture has, also, a pseudo-brecciated structure, in which fragments are obscurely arranged in planes parallel to those of the stratification, and are conspicuous on the weathered surfaces. The fragments are angular or rounded, small or large, and consist of bluish or reddish compact feldspathic matter, in which a few acicular crystals of feldspar can sometimes be seen. The fragments often blend at their edges into the surrounding granular mass, and seem due to a kind of concretionary action.

These singular rocks are traversed by many copper veins, and appear to rest conformably on the granular mixture (in parts as fine-grained as a sandstone) of quartz, mica, hornblende, and feldspar; and this on fine-grained, common gneiss; and this on a laminated mass, composed of pinkish _orthitic_ feldspar, including a few specks of hornblende; and lastly, this on granite, which together with andesitic rocks, form the surrounding district.

_Coquimbo: Mining district of Arqueros._—At Coquimbo the porphyritic conglomerate formation approaches nearer to the Pacific than in any other part of Chile visited by me, being separated from the coast by a tract only a few miles broad of the usual plutonic rocks, with the addition of a porphyry having a red euritic base. In proceeding to the mines of Arqueros, the strata of porphyritic conglomerate are at first nearly horizontal, an unusual circumstance, and afterwards they dip gently to S.S.E. After having ascended to a considerable height, we come to an undulatory district in which the famous silver mines are situated; my examination was chiefly confined to those of S. Rosa. Most of the rocks in this district are stratified, dipping in various directions, and many of them are of so singular a nature, that at the risk of being tedious I must briefly describe them. The commonest variety is a dull-red, compact, finely brecciated stone, containing much iron and innumerable white crystallised particles of carbonate of lime, and minute extraneous fragments. Another variety is almost equally common near S. Rosa; it has a bright green, scanty basis, including distinct crystals and patches of white carbonate of lime, and grains of red, semi-micaceous oxide of iron; in parts the basis becomes dark green, and assumes an obscure crystalline arrangement, and occasionally in parts it becomes soft and slightly translucent like soapstone. These red and green rocks are often quite distinct, and often pass into each other; the passage being sometimes affected by a fine brecciated structure, particles of the red and green matter being mingled together. Some of the varieties appear gradually to become porphyritic with feldspar; and all of them are easily fusible into pale or dark-coloured beads, strongly attracted by the magnet. I should perhaps have mistaken several of these stratified rocks for submarine lavas, like some of those described at the Puente del Inca, had I not examined, a few leagues eastward of this point, a fine series of analogous but less metamorphosed, sedimentary beds belonging to the gypseous formation, and probably derived from a volcanic source.

This formation is intersected by numerous metalliferous veins, running, though irregularly, N.W. and S.E., and generally at right angles to the many dikes. The veins consist of native silver, of muriate of silver, an amalgam of silver, cobalt, antimony, and arsenic,[1] generally embedded in sulphate of barytes. I was assured by Mr. Lambert, that native copper without a trace of silver has been found in the same vein with native silver without a trace of copper. At the mines of Aristeas, the silver veins are said to be unproductive as soon as they pass into the green strata, whereas at S. Rosa, only two or three miles distant, the reverse happens; and at the time of my visit, the miners were working through a red stratum, in the hope of the vein becoming productive in the underlying green sedimentary mass. I have a specimen of one of these green rocks, with the usual granules of white calcareous spar and red oxide of iron, abounding with disseminated particles of glittering native and muriate of silver, yet taken at the distance of one yard from any vein,—a circumstance, as I was assured, of very rare occurrence.

[1] See the Report on M. Domeyko’s account of those mines, in the “Comptes Rendus,” tome xiv, p. 560.

_Section eastward, up the Valley of Coquimbo._—After passing for a few miles over the coast granitic series, we come to the porphyritic conglomerate, with its usual characters, and with some of the beds distinctly displaying their mechanical origin. The strata, where first met with, are, as before stated, only slightly inclined; but near the Hacienda of Pluclaro, we come to an anticlinal axis, with the beds much dislocated and shifted by a great fault, of which not a trace is externally seen in the outline of the hill. I believe that this anticlinal axis can be traced northwards, into the district of Arqueros, where a conspicuous hill called Cerro Blanco, formed of a harsh, cream-coloured euritic rock, including a few crystals of reddish feldspar, and associated with some purplish claystone porphyry, seems to fall on a line of elevation. In descending from the Arqueros district, I crossed on the northern border of the valley, strata inclined eastward from the Pluclaro axis: on the porphyritic conglomerate there rested a mass, some hundred feet thick, of brown argillaceous limestone, in parts crystalline, and in parts almost composed of _Hippurites Chilensis,_ d’Orbigny; above this came a black calcareous shale, and on it a red conglomerate. In the brown limestone, with the Hippurites, there was an impression of a Pecten and a coral, and great numbers of a large Gryphæa, very like, and, according to Professor E. Forbes, probably identical with _G. Orientalis,_ Forbes MS.,—a cretaceous species (probably upper greensand) from Verdachellum, in Southern India. These fossils seem to occupy nearly the same position with those at the Puente del Inca,—namely, at the top of the porphyritic conglomerate, and at the base of the gypseous formation.

A little above the Hacienda of Pluclaro, I made a detour on the northern side of the valley, to examine the superincumbent gypseous strata, which I estimated at 6,000 feet in thickness. The uppermost beds of the porphyritic conglomerate, on which the gypseous strata conformably rest, are variously coloured, with one very singular and beautiful stratum composed of purple pebbles of various kinds of porphyry, embedded in white calcareous spar, including cavities lined with bright-green crystallised epidote. The whole pile of strata belonging to both formations is inclined, apparently from the above-mentioned axis of Pluclaro, at an angle of between 20 and 30 degrees to the east. I will here give a section of the principal beds met with in crossing the entire thickness of the gypseous strata.

Firstly: above the porphyritic conglomerate formation, there is a fine-grained, red, crystalline sandstone.

Secondly: a thick mass of smooth-grained, calcareo-aluminous, shaly rock, often marked with dendritic manganese, and having, where most compact, the external appearance of honestone. It is easily fusible. I shall for the future, for convenience’ sake, call this variety pseudo-honestone. Some of the varieties are quite black when freshly broken, but all weather into a yellowish-ash coloured, soft, earthy substance, precisely as is the case with the compact shaly rocks of the Peuquenes range. This stratum is of the same general nature with many of the beds near Los Hornos in the Illapel section. In this second bed, or in the underlying red sandstone (for the surface was partially concealed by detritus), there was a thick mass of gypsum, having the same mineralogical characters with the great beds described in our sections across the Cordillera.

Thirdly: a thick stratum of fine-grained, red, sedimentary matter, easily fusible into a white glass, like the basis of claystone porphyry; but in parts jaspery, in parts brecciated, and including crystalline specks of carbonate of lime. In some of the jaspery layers, and in some of the black siliceous slaty bands, there were irregular seams of imperfect pitchstone, undoubtedly of metamorphic origin, and other seams of brown, crystalline limestone. Here, also, were masses, externally resembling ill-preserved silicified wood.

Fourthly and fifthly: calcareous pseudo-honestone; and a thick stratum concealed by detritus.

Sixthly: a thinly stratified mass of bright green, compact, smooth-grained, calcareo-argillaceous stone, easily fusible, and emitting a strong aluminous odour: the whole has a highly angulo-concretionary structure; and it resembles, to a certain extent, some of the upper tufaceo-infusorial deposits of the Patagonian tertiary formation. It is in its nature allied to our pseudo-honestone, and it includes well characterised layers of that variety; and other layers of a pale green, harder, and brecciated variety; and others of red sedimentary matter, like that of bed Three. Some pebbles of porphyries are embedded in the upper part.

Seventhly: red sedimentary matter or sandstone like that of bed One, several hundred feet in thickness, and including jaspery layers, often having a finely brecciated structure.

Eighthly: white, much indurated, almost crystalline tuff, several hundred feet in thickness, including rounded grains of quartz and particles of green matter like that of bed Six. Parts pass into a very pale green, semi-porcellanic stone.

Ninthly: red or brown coarse conglomerate, three or four hundred feet thick, formed chiefly of pebbles of porphyries, with volcanic particles, in an arenaceous, non-calcareous, fusible basis: the upper two feet are arenaceous without any pebbles.

Tenthly: the last and uppermost stratum here exhibited, is a compact, slate-coloured porphyry, with numerous elongated crystals of glassy feldspar, from one hundred and fifty to two hundred feet in thickness; it lies strictly conformably on the underlying conglomerate, and is undoubtedly a submarine lava.

This great pile of strata has been broken up in several places by intrusive hillocks of purple claystone porphyry, and by dikes of porphyritic greenstone: it is said that a few poor metalliferous veins have been discovered here. From the fusible nature and general appearance of the finer-grained strata, they probably owe their origin (like the allied beds of the Uspallata range, and of the Upper Patagonian tertiary formations), to gentle volcanic eruptions, and to the abrasion of volcanic rocks. Comparing these beds with those in the mining district of Arqueros, we see at both places rocks easily fusible, of the same peculiar bright green and red colours, containing calcareous matter, often having a finely brecciated structure, often passing into each other, and often alternating together: hence I cannot doubt that the only difference between them, lies in the Arqueros beds having been more metamorphosed (in conformity with their more dislocated and injected condition), and consequently in the calcareous matter, oxide of iron and green colouring matter, having been segregated under a more crystalline form.

The strata are inclined, as before stated, from 20° to 30° eastward, towards an irregular north and south chain of andesitic porphyry and of porphyritic greenstone, where they are abruptly cut off. In the valley of Coquimbo, near to the H. of Gualliguaca, similar plutonic rocks are met with, apparently a southern prolongation of the above chain; and eastward of it we have an escarpment of the porphyritic conglomerate, with the strata inclined at a small angle eastward, which makes the third escarpment, including that nearest the coast. Proceeding up the valley we come to another north and south line of granite, andesite, and blackish porphyry, which seem to lie in an irregular trough of the porphyritic conglomerate. Again, on the south side of the R. Claro, there are some irregular granitic hills, which have thrown off the strata of porphyritic conglomerate to the N.W. by W.; but the stratification here has been much disturbed. I did not proceed any farther up the valley, and this point is about two-thirds of the distance between the Pacific and the main Cordillera.

I will describe only one other section, namely, on the north side of the R. Claro, which is interesting from containing fossils: the strata are much dislocated by faults and dikes, and are inclined to the north, towards a mountain of andesite and porphyry, into which they appear to become almost blended. As the beds approach this mountain, their inclination increases up to an angle of 70°, and in the upper part, the rocks become highly metamorphosed. The lowest bed visible in this section, is a purplish hard sandstone. Secondly, a bed two or three hundred feet thick, of a white siliceous sandstone, with a calcareous cement, containing seams of slaty sandstone, and of hard yellowish-brown (dolomitic?) limestone; numerous, well-rounded, little pebbles of quartz are included in the sandstone. Thirdly, a dark coloured limestone with some quartz pebbles, from fifty to sixty feet in thickness, containing numerous silicified shells, presently to be enumerated. Fourthly, very compact, calcareous, jaspery sandstone, passing into (fifthly) a great bed, several hundred feet thick, of conglomerate, composed of pebbles of white, red, and purple porphyries, of sandstone and quartz, cemented by calcareous matter. I observed that some of the finer parts of this conglomerate were much indurated within a foot of a dike eight feet in width, and were rendered of a paler colour with the calcareous matter segregated into white crystallised particles; some parts were stained green from the colouring matter of the dike. Sixthly, a thick mass, obscurely stratified, of a red sedimentary stone or sandstone, full of crystalline calcareous matter, imperfect crystals of oxide of iron, and I believe of feldspar, and therefore closely resembling some of the highly metamorphosed beds at Arqueros: this bed was capped by, and appeared to pass in its upper part into, rocks similarly coloured, containing calcareous matter, and abounding with minute crystals, mostly elongated and glassy, of reddish albite. Seventhly, a conformable stratum of fine reddish porphyry with large crystals of (albitic?) feldspar; probably a submarine lava. Eighthly, another conformable bed of green porphyry, with specks of green earth and cream-coloured crystals of feldspar. I believe that there are other superincumbent crystalline strata and submarine lavas, but I had not time to examine them.

The upper beds in this section probably correspond with parts of the great gypseous formation; and the lower beds of red sandstone conglomerate and fossiliferous limestone no doubt are the equivalents of the Hippurite stratum, seen in descending from Arqueros to Pluclaro, which there lies conformably upon the porphyritic conglomerate formation. The fossils found in the third bed, consist of:—

Pecten Dufreynoyi, d’Orbigny, “Voyage, Part Pal.” This species, which occurs here in vast numbers, according to M. D’Orbigny, resembles certain cretaceous forms.

Ostrea hemispherica, d’Orbigny, “Voyage” etc. Also resembles, according to the same author, cretaceous forms.

Terebratula ænigma, d’Orbigny, “Voyage” etc. (Pl. XXII, Figs. 10-12.) Is allied, according to M. d’Orbigny, to T. concinna from the Forest Marble. A series of this species, collected in several localities hereafter to be referred to, has been laid before Professor Forbes; and he informs me that many of the specimens are almost undistinguishable from our oolitic T. tetrædra, and that the varieties amongst them are such as are found in that variable species. Generally speaking, the American specimens of T. ænigma may be distinguished from the British T. tetrædra, by the surface having the ribs sharp and well-defined to the beak, whilst in the British species they become obsolete and smoothed down; but this difference is not constant. Professor Forbes adds, that, possibly, internal characters may exist, which would distinguish the American species from its European allies.

Spirifer linguiferoides, E. Forbes. Professor Forbes states that this species is very near to S. linguifera of Phillips (a carboniferous limestone fossil), but probably distinct. M. d’Orbigny considers it as perhaps indicating the Jurassic period.

Ammonites, imperfect impression of.

M. Domeyko has sent to France a collection of fossils, which, I presume, from the description given, must have come from the neighbourhood of Arqueros; they consist of:—

Pecten Dufreynoyi, d’Orbigny, “Voyage” Part Pal. Ostrea hemispherica, d’Orbigny, “Voyage” Part Pal. Turritella Andii, d’Orbigny, “Voyage” Part Pal. (Pleurotomaria Humboldtii of Von Buch). Hippurites Chilensis, d’Orbigny, “Voyage” Part Pal. The specimens of this Hippurite, as well as those I collected in my descent from Arqueros, are very imperfect; but in M. d’Orbigny’s opinion they resemble, as does the Turritella Andii, cretaceous (upper greensand) forms.

Nautilus Domeykus, d’Orbigny, “Voyage” Part Pal. Terebratula ænigma, d’Orbigny, “Voyage” Part Pal. Terebratula ignaciana, d’Orbigny, “Voyage” Part Pal. This latter species was found by M. Domeyko in the same block of limestone with the T. ænigma. According to M. d’Orbigny, it comes near to T. ornithocephala from the Lias. A series of this species collected at Guasco, has been examined by Professor E. Forbes, and he states that it is difficult to distinguish between some of the specimens and the T. hastata from the mountain limestone; and that it is equally difficult to draw a line between them and some Marlstone Terebratulæ. Without a knowledge of the internal structure, it is impossible at present to decide on their identity with analogous European forms.

The remarks given on the several foregoing shells, show that, in M. d’Orbigny’s opinion, the Pecten, Ostrea, Turritella, and Hippurite indicate the cretaceous period; and the Gryphæa appears to Professor Forbes to be identical with a species, associated in Southern India with unquestionably cretaceous forms. On the other hand, the two Terebratulæ and the Spirifer point, in the opinion both of M. d’Orbigny and Professor Forbes, to the oolitic series. Hence M. d’Orbigny, not having himself examined this country, has concluded that there are here two distinct formations; but the Spirifer and T. ænigma were certainly included in the same bed with the Pecten and Ostrea, whence I extracted them; and the geologist M. Domeyko sent home the two Terebratulæ with the other-named shells, from the same locality, without specifying that they came from different beds. Again, as we shall presently see, in a collection of shells given me from Guasco, the same species, and others presenting analogous differences, are mingled together, and are in the same condition; and lastly, in three places in the valley of Copiapo, I found some of these same species similarly grouped. Hence there cannot be any doubt, highly curious though the fact be, that these several fossils, namely, the Hippurites, Gryphæa, Ostrea, Pecten, Turritella, Nautilus, two Terebratulæ, and Spirifer all belong to the same formation, which would appear to form a passage between the oolitic and cretaceous systems of Europe. Although aware how unusual the term must sound, I shall, for convenience’ sake, call this formation cretaceo-oolitic. Comparing the sections in this valley of Coquimbo with those in the Cordillera described in the last chapter, and bearing in mind the character of the beds in the intermediate district of Los Hornos, there is certainly a close general mineralogical resemblance between them, both in the underlying porphyritic conglomerate, and in the overlying gypseous formation. Considering this resemblance, and that the fossils from the Puente del Inca at the base of the gypseous formation, and throughout the greater part of its entire thickness on the Peuquenes range, indicate the Neocomian period,—that is, the dawn of the cretaceous system, or, as some have believed, a passage between this latter and the oolitic series—I conclude that probably the gypseous and associated beds in all the sections hitherto described, belong to the same great formation, which I have denominated—cretaceo-oolitic. I may add, before leaving Coquimbo, that M. Gay found in the neighbouring Cordillera, at the height of 14,000 feet above the sea, a fossiliferous formation, including a Trigonia and Pholadomya;[2]—both of which genera occur at the Puente del Inca.

[2] D’Orbigny, “Voyage,” Part Géolog., p. 242.

_Coquimbo to Guasco._—The rocks near the coast, and some way inland, do not differ from those described northwards of Valparaiso: we have much greenstone, syenite, feldspathic and jaspery slate, and grauwackes having a basis like that of claystone; there are some large tracts of granite, in which the constituent minerals are sometimes arranged in folia, thus composing an imperfect gneiss. There are two large districts of mica-schists, passing into glossy clay-slate, and resembling the great formation in the Chonos Archipelago. In the valley of Guasco, an escarpment of porphyritic conglomerate is first seen high up the valley, about two leagues eastward of the town of Ballenar. I heard of a great gypseous formation in the Cordillera; and a collection of shells made there was given me. These shells are all in the same condition, and appear to have come from the same bed: they consist of:—

Turritella Andii, d’Orbigny, “Voyage,” Part Pal. Pecten Dufreynoyi, d’Orbigny, “Voyage,” Part Pal. Terebatula ignaciana, d’Orbigny, “Voyage,” Part Pal. The relations of these species have been given under the head of Coquimbo.

Terebratula ænigma, d’Orbigny, “Voyage,” Part Pal. This shell M. d’Orbigny does not consider identical with his T. ænigma, but near to T. obsoleta. Professor Forbes thinks that it is certainly a variety of T. ænigma: we shall meet with this variety again at Copiapo.

Spirifer Chilensis, E. Forbes. Professor Forbes remarks that this fossil resembles several carboniferous limestone Spirifers; and that it is also related to some liassic species, as S. Wolcotii.

If these shells had been examined independently of the other collections, they would probably have been considered, from the characters of the two Terebratulæ, and from the Spirifer, as oolitic; but considering that the first species, and according to Professor Forbes, the four first, are identical with those from Coquimbo, the two formations no doubt are the same, and may, as I have said, be provisionally called cretaceo-oolitic.

_Valley of Copiapo._—The journey from Guasco to Copiapo, owing to the utterly desert nature of the country, was necessarily so hurried, that I do not consider my notes worth giving. In the valley of Copiapo some of the sections are very interesting. From the sea to the town of Copiapo, a distance estimated at thirty miles, the mountains are composed of greenstone, granite, andesite, and blackish porphyry, together with some dusky-green feldspathic rocks, which I believe to be altered clay-slate: these mountains are crossed by many brown-coloured dikes, running north and south. Above the town, the main valley runs in a south-east and even more southerly course towards the Cordillera, where it is divided into three great ravines, by the northern one of which, called Jolquera, I penetrated for a short distance. The section, Fig. 3 in Plate V, gives an eye-sketch of the structure and composition of the mountains on both sides of this valley: a straight east and west line from the town to the Cordillera is perhaps not more than thirty miles, but along the valley the distance is much greater. Wherever the valley trended very southerly, I have endeavoured to contract the section into its true proportion. This valley, I may add, rises much more gently than any other valley which I saw in Chile.

To commence with our section, for a short distance above the town we have hills of the granitic series, together with some of that rock [A], which I suspect to be altered clay-slate, but which Professor G. Rose, judging from specimens collected by Meyen at P. Negro, states is serpentine passing into greenstone. We then come suddenly to the great gypseous formation [B], without having passed over, differently from, in all the sections hitherto described, any of the porphyritic conglomerate. The strata are at first either horizontal or gently inclined westward; then highly inclined in various directions, and contorted by underlying masses of intrusive rocks; and lastly, they have a regular eastward dip, and form a tolerably well pronounced north and south line of hills. This formation consists of thin strata, with innumerable alternations, of black, calcareous slate-rock, of calcareo-aluminous stones like those at Coquimbo, which I have called pseudo-honestones of green jaspery layers, and of pale-purplish, calcareous, soft rotten-stone, including seams and veins of gypsum. These strata are conformably overlaid by a great thickness of thinly stratified, compact limestone with included crystals of carbonate of lime. At a place called Tierra Amarilla, at the foot of a mountain thus composed there is a broad vein, or perhaps stratum, of a beautiful and curious crystallised mixture, composed, according to Professor G. Rose,[3] of sulphate of iron under two forms, and of the sulphates of copper and alumina: the section is so obscure that I could not make out whether this vein or stratum occurred in the gypseous formation, or more probably in some underlying masses [A], which I believe are altered clay-slate.

[3] Meyen’s “Reise,” etc., Th. I, s. 394.

_Second axis of elevation._—After the gypseous masses [B], we come to a line of hills of unstratified porphyry [C], which on their eastern side blend into strata of great thickness of porphyritic conglomerate, dipping eastward. This latter formation, however, here has not been nearly so much metamorphosed as in most parts of Central Chile; it is composed of beds of true purple claystone porphyry, repeatedly alternating with thick beds of purplish-red conglomerate with the well-rounded, large pebbles of various porphyries, not blended together. _Third axis of elevation._—Near the ravine of Los Hornitos, there is a well-marked line of elevation, extending for many miles in a N.N.E. and S.S.W. direction, with the strata dipping in most parts (as in the second axis) only in one direction, namely, eastward at an average angle of between 30° and 40°. Close to the mouth of the valley, however, there is, as represented in the section, a steep and high mountain [D], composed of various green and brown intrusive porphyries enveloped with strata, apparently belonging to the upper parts of the porphyritic conglomerate, and dipping both eastward and westward. I will describe the section seen on the eastern side of this mountain [D], beginning at the base with the lowest bed visible in the porphyritic conglomerate, and proceeding upwards through the gypseous formation. Bed 1 consists of reddish and brownish porphyry varying in character, and in many parts highly amygdaloidal with carbonate of lime, and with bright green and brown bole. Its upper surface is throughout clearly defined, but the lower surface is in most parts indistinct, and towards the summit of the mountain [D] quite blended into the intrusive porphyries. Bed 2, a pale lilac, hard but not heavy stone, slightly laminated, including small extraneous fragments, and imperfect as well as some perfect and glassy crystals of feldspar; from one hundred and fifty to two hundred feet in thickness. When examining it in situ, I thought it was certainly a true porphyry, but my specimens now lead me to suspect that it possibly may be a metamorphosed tuff. From its colour it could be traced for a long distance, overlying in one part, quite conformably to the porphyry of bed 1, and in another not distant part, a very thick mass of conglomerate, composed of pebbles of a porphyry chiefly like that of bed 1: this fact shows how the nature of the bottom formerly varied in short horizontal distances. Bed 3, white, much indurated tuff, containing minute pebbles, broken crystals, and scales of mica, varies much in thickness. This bed is remarkable from containing many globular and pear-shaped, externally rusty balls, from the size of an apple to a man’s head, of very tough, slate-coloured porphyry, with imperfect crystals of feldspar: in shape these balls do not resemble pebbles, _and i believe that they are subaqueous volcanic bombs_; they differ from _subaerial_ bombs only in not being vesicular. Bed 4; a dull purplish-red, hard conglomerate, with crystallised particles and veins of carbonate of lime, from three hundred to four hundred feet in thickness. The pebbles are of claystone porphyries of many varieties; they are tolerably well rounded, and vary in size from a large apple to a man’s head. This bed includes three layers of coarse, black, calcareous, somewhat slaty rock: the upper part passes into a compact red sandstone.

In a formation so highly variable in mineralogical nature, any division not founded on fossil remains, must be extremely arbitrary: nevertheless, the beds below the last conglomerate may, in accordance with all the sections hitherto described, be considered as belonging to the porphyritic conglomerate, and those above it to the gypseous formation, marked [E] in the section. The part of the valley in which the following beds are seen is near Potrero Seco. Bed 5, compact, fine-grained, pale greenish-grey, non-calcareous, indurated mudstone, easily fusible into a pale green and white glass. Bed 6, purplish, coarse-grained, hard sandstone, with broken crystals of feldspar and crystallised particles of carbonate of lime; it possesses a slightly nodular structure. Bed 7, blackish-grey, much indurated, calcareous mudstone, with extraneous particles of unequal size; the whole being in parts finely brecciated. In this mass there is a stratum, twenty feet in thickness, of impure gypsum. Bed 8, a greenish mudstone, with several layers of gypsum. Bed 9, a highly indurated, easily fusible, white tuff, thickly mottled with ferruginous matter, and including some white semi-porcellanic layers, which are interlaced with ferruginous veins. This stone closely resembles some of the commonest varieties in the Uspallata chain. Bed 10, a thick bed of rather bright green, indurated mudstone or tuff, with a concretionary nodular structure so strongly developed that the whole mass consists of balls. I will not attempt to estimate the thickness of the strata in the gypseous formation hitherto described, but it must certainly be very many hundred feet. Bed 11 is at least 800 feet in thickness: it consists of thin layers of whitish, greenish, or more commonly brown, fine-grained, indurated tuffs, which crumble into angular fragments: some of the layers are semi-porcellanic, many of them highly ferruginous, and some are almost composed of carbonate of lime and iron with drusy cavities lined with quartzf-crystals. Bed 12, dull purplish or greenish or dark-grey, very compact and much indurated mudstone: estimated at 1,500 feet in thickness: in some parts this rock assumes the character of an imperfect coarse clay-slate; but viewed under a lens, the basis always has a mottled appearance, with the edges of the minute component particles blending together. Parts are calcareous, and there are numerous veins of highly crystalline carbonate of lime charged with iron. The mass has a nodular structure, and is divided by only a few planes of stratification: there are, however, two layers, each about eighteen inches thick, of a dark brown, finer-grained stone, having a conchoidal, semi-porcellanic fracture, which can be followed with the eye for some miles across the country.

I believe this last great bed is covered by other nearly similar alternations; but the section is here obscured by a tilt from the next porphyritic chain, presently to be described. I have given this section in detail, as being illustrative of the general character of the mountains in this neighbourhood; but it must not be supposed that any one stratum long preserves the same character. At a distance of between only two and three miles the green mudstones and white indurated tuffs are to a great extent replaced by red sandstone and black calcareous shaly rocks, alternating together. The white indurated tuff, bed 11, here contains little or no gypsum, whereas on the northern and opposite side of the valley, it is of much greater thickness and abounds with layers of gypsum, some of them alternating with thin seams of crystalline carbonate of lime. The uppermost, dark-coloured, hard mudstone, bed 12, is in this neighbourhood the most constant stratum. The whole series differs to a considerable extent, especially in its upper part, from that met with at [BB], in the lower part of the valley; nevertheless, I do not doubt that they are equivalents. _Fourth axis of elevation (Valley of Copiapo)._—This axis is formed of a chain of mountains [F], of which the central masses (near La Punta) consist of andesite containing green hornblende and coppery mica, and the outer masses of greenish and black porphyries, together with some fine lilac-coloured claystone porphyry; all these porphyries being injected and broken up by small hummocks of andesite. The central great mass of this latter rock, is covered on the eastern side by a black, fine-grained, highly micaceous slate, which, together with the succeeding mountains of porphyry, are traversed by numerous white dikes, branching from the andesite, and some of them extending in straight lines, to a distance of at least two miles. The mountains of porphyry eastward of the micaceous schist soon, but gradually, assume (as observed in so many other cases) a stratified structure, and can then be recognised as a part of the porphyritic conglomerate formation. These strata [G] are inclined at a high angle to the S.E., and form a mass from fifteen hundred to two thousand feet in thickness. The gypseous masses to the west already described, dip directly towards this axis, with the strata only in a few places (one of which is represented in the section) thrown from it: hence this fourth axis is mainly uniclinal towards the S.E., and just like our third axis, only locally anticlinal.

The above strata of porphyritic conglomerate [G] with their south-eastward dip, come abruptly up against beds of the gypseous formation [H], which are gently, but irregularly, inclined westward: so that there is here a synclinal axis and great fault. Further up the valley, here running nearly north and south, the gypseous formation is prolonged for some distance; but the stratification is unintelligible, the whole being broken up by faults, dikes, and metalliferous veins. The strata consist chiefly of red calcareous sandstones, with numerous veins in the place of layers, of gypsum; the sandstone is associated with some black calcareous slate-rock, and with green pseudo-honestones, passing into porcelain-jasper. Still further up the valley, near Las Amolanas [I], the gypseous strata become more regular, dipping at an angle of between 30 and 40 degrees to W.S.W., and conformably overlying, near the mouth of the ravine of Jolquera, strata [K] of porphyritic conglomerate. The whole series has been tilted by a partially concealed axis [L], of granite, andesite, and a granitic mixture of white feldspar, quartz, and oxide of iron.

_Fifth axis of elevation (Valley of Copiapo, near Las Amolanas)._—I will describe in some detail the beds [I] seen here, which, as just stated, dip to W.S.W., at an angle of from 30° to 40°. I had not time to examine the underlying porphyritic conglomerate, of which the lowest beds, as seen at the mouth of the Jolquera, are highly compact, with crystals of red oxide of iron; and I am not prepared to say whether they are chiefly of volcanic or metamorphic origin. On these beds there rests a coarse purplish conglomerate, very little metamorphosed, composed of pebbles of porphyry, but remarkable from containing one pebble of granite;—of which fact no instance has occurred in the sections hitherto described. Above this conglomerate, there is a black siliceous claystone, and above it numerous alternations of dark-purplish and green porphyries, which may be considered as the uppermost limit of the porphyritic conglomerate formation.

Above these porphyries comes a coarse, arenaceous conglomerate, the lower half white and the upper half of a pink colour, composed chiefly of pebbles of various porphyries, but with some of red sandstone and jaspery rocks. In some of the more arenaceous parts of the conglomerate, there was an oblique or current lamination; a circumstance which I did not elsewhere observe. Above this conglomerate, there is a vast thickness of thinly stratified, pale-yellowish, siliceous sandstone, passing into a granular quartz-rock, used for grindstones (hence the name of the place _ Las Amolanas_), and certainly belonging to the gypseous formation, as does probably the immediately underlying conglomerate. In this yellowish sandstone there are layers of white and pale-red siliceous conglomerate; other layers with small, well-rounded pebbles of white quartz, like the bed at the R. Claro at Coquimbo; others of a greenish, fine-grained, less siliceous stone, somewhat resembling the pseudo-honestones lower down the valley; and lastly, others of a black calcareous shale-rock. In one of the layers of conglomerate, there was embedded a fragment of mica-slate, of which this is the first instance; hence perhaps, it is from a formation of mica-slate, that the numerous small pebbles of quartz, both here and at Coquimbo, have been derived. Not only does the siliceous sandstone include layers of the black, thinly stratified, not fissile, calcareous shale-rock, but in one place the whole mass, especially the upper part, was, in a marvellously short horizontal distance, after frequent alternations, replaced by it. When this occurred, a mountain-mass, several thousand feet in thickness was thus composed; the black calcareous shale-rock, however, always included some layers of the pale-yellowish siliceous sandstone, of the red conglomerate, and of the greenish jaspery and pseudo-honestone varieties. It likewise included three or four widely separated layers of a brown limestone, abounding with shells immediately to be described. This pile of strata was in parts traversed by many veins of gypsum. The calcareous shale-rock, though when freshly broken quite black, weathers into an ash- colour: in which respect and in general appearance, it perfectly resembles those great fossiliferous beds of the Peuquenes range, alternating with gypsum and red sandstone, described in the last chapter.

The shells out of the layers of brown limestone, included in the black calcareous shale-rock, which latter, as just stated, replaces the white siliceous sandstone, consist of:—

Pecten Dufreynoyi, d’Orbigny, “Voyage,” Part Pal. Turritella Andii, d’Orbigny, “Voyage,” Part Pal.

Astarte Darwinii, E. Forbes. Gryphæa Darwinii, E. Forbes. An intermediate form between G. gigantea and G. incurva.

Gryphæa nov. spec.?, E. Forbes. Perna Americana, E. Forbes. Avicula, nov. spec. Considered by Mr. G. B. Sowerby as the A. echinata, by M. d’Orbigny as certainly a new and distinct species, having a Jurassic aspect. The specimen has been unfortunately lost.

Terebratula ænigma, d’Orbigny, (var. of do. E. Forbes.) This is the same variety, with that from Guasco, considered by M. D’Orbigny to be a distinct species from his T. ænigma, and related to T. obsoleta.

Plagiostoma and Ammonites, fragments of.

The lower layers of the limestone contained thousands of the Gryphæa; and the upper ones as many of the Turritella, with the Gryphæa (nov. species) and Serpulæ adhering to them; in all the layers, the Terebratula and fragments of the Pecten were included. It was evident, from the manner in which species were grouped together, that they had lived where now embedded. Before making any further remarks, I may state, that higher up this same valley we shall again meet with a similar association of shells; and in the great Despoblado Valley, which branches off near the town from that of Copiapo, the Pecten Dufreynoyi, some Gryphites (I believe G. Darwinii), and the _ true_ Terebratula ænigma of d’Orbigny were found together in an equivalent formation, as will be hereafter seen. A specimen also, I may add, of the true T. ænigma, was given me from the neighbourhood of the famous silver mines of Chanuncillo, a little south of the valley of the Copiapo, and these mines, from their position, I have no doubt, lie within the great gypseous formation: the rocks close to one of the silver veins, judging from fragments shown me, resemble those singular metamorphosed deposits from the mining district of Arqueros near Coquimbo.

I will reiterate the evidence on the association of these several shells in the several localities.

_Coquimbo._

In the same bed, Rio Claro: Pecten Dufreynoyi. Ostrea hemispherica. Terebratula ænigma. Spirifer linguiferoides.

Same bed, near Arqueros: Hippurites Chilensis. Gryphæa orientalis.

Collected by M. Domeyko from the same locality, apparently near Arqueros: Terebratula ænigma and Terebratula ignaciana, in same block of limestone. Pecten Dufreynoyi. Ostrea hemispherica. Hippurites Chilensis. Turritella Andii. Nautilus Domeykus.

_Guasco._

In a collection from the Cordillera, given me: the specimens all in the same condition: Pecten Dufreynoyi. Turritella Andii. Terebratula ignaciana. Terebratula ænigma, _var._ Spirifer Chilensis.

_Copiapo._

Mingled together in alternating beds in the main valley of Copiapo near Las Amolanas, and likewise higher up the valley: Pecten Dufreynoyi. Turritella Andii. Terebratula ænigma, _var._, as at Guasco. Astarte Darwinii. Gryphæa Darwinii. Gryphæa nov. species? Perna Americana. Avicula, nov. species.

Main valley of Copiapo, apparently same formation with that of Amolanas: Terebratula ænigma (true).

In the same bed, high up the great lateral valley of the Despoblado, in the ravine of Maricongo: Terebratula ænigma (true). Pecten Dufreynoyi. Gryphæa Darwinii?

Considering this table, I think it is impossible to doubt that all these fossils belong to the same formation. If, however, the species from Las Amolanas, in the Valley of Copiapo, had, as in the case of those from Guasco, been separately examined, they would probably have been ranked as oolitic; for, although no Spirifers were found here, all the other species, with the exception of the Pecten, Turritella, and Astarte, have a more ancient aspect than cretaceous forms. On the other hand, taking into account the evidence derived from the cretaceous character of these three shells, and of the Hippurites, Gryphæa orientalis, and Ostrea, from Coquimbo, we are driven back to the provisional name already used of cretaceo-oolitic. From geological evidence, I believe this formation to be the equivalent of the Neocomian beds of the Cordillera of Central Chile.

To return to our section near Las Amolanas:—Above the yellow siliceous sandstone, or the equivalent calcareous slate-rock, with its bands of fossil-shells, according as the one or other prevails, there is a pile of strata, which cannot be less than from two to three thousand feet in thickness, in main part composed of a coarse, bright red conglomerate, with many intercalated beds of red sandstone, and some of green and other coloured porcelain-jaspery layers. The included pebbles are well-rounded, varying from the size of an egg to that of a cricket-ball, with a few larger; and they consist chiefly of porphyries. The basis of the conglomerate, as well as some of the alternating thin beds, are formed of a red, rather harsh, easily fusible sandstone, with crystalline calcareous particles. This whole great pile is remarkable from the thousands of huge, embedded, silicified trunks of trees, one of which was eight feet long, and another eighteen feet in circumference: how marvellous it is, that every vessel in so thick a mass of wood should have been converted into silex! I brought home many specimens, and all of them, according to Mr. R. Brown, present a coniferous structure.

Above this great conglomerate, we have from two to three hundred feet in thickness of red sandstone; and above this, a stratum of black calcareous slate-rock, like that which alternates with and replaces the underlying yellowish-white, siliceous sandstone. Close to the junction between this upper black slate-rock and the upper red sandstone, I found the Gryphæa Darwinii, the Turritella Andii, and vast numbers of a bivalve, too imperfect to be recognised. Hence we see that, as far as the evidence of these two shells serves—and the Turritella is an eminently characteristic species—the whole thickness of this vast pile of strata belongs to the same age. Again, above the last-mentioned upper red sandstone, there were several alternations of the black, calcareous slate-rock; but I was unable to ascend to them. All these uppermost strata, like the lower ones, vary extremely in character in short horizontal distances. The gypseous formation, as here seen, has a coarser, more mechanical texture, and contains much more siliceous matter than the corresponding beds lower down the valley. Its total thickness, together with the upper beds of the porphyritic conglomerate, I estimated at least at 8,000 feet; and only a small portion of the porphyritic conglomerate, which on the eastern flank of the fourth axis of elevation appeared to be from fifteen hundred to two thousand feet thick, is here included. As corroborative of the great thickness of the gypseous formation, I may mention that in the Despoblado Valley (which branches from the main valley a little above the town of Copiapo) I found a corresponding pile of red and white sandstones, and of dark, calcareous, semi-jaspery mudstones, rising from a nearly level surface and thrown into an absolutely vertical position; so that, by pacing, I ascertained their thickness to be nearly two thousand seven hundred feet; taking this as a standard of comparison, I estimated the thickness of the strata _above_ the porphyritic conglomerate at 7,000 feet.

The fossils before enumerated, from the limestone-layers in the whitish siliceous sandstone, are now covered, on the least computation, by strata from 5,000 to 6,000 feet in thickness. Professor E. Forbes thinks that these shells probably lived at a depth of from about 30 to 40 fathoms, that is from 180 to 240 feet; anyhow, it is impossible that they could have lived at the depth of from 5,000 to 6,000 feet. Hence in this case, as in that of the Puente del Inca, we may safely conclude that the bottom of the sea on which the shells lived, subsided, so as to receive the superincumbent submarine strata: and this subsidence must have taken place during the existence of these shells; for, as I have shown, some of them occur high up as well as low down in the series. That the bottom of the sea subsided, is in harmony with the presence of the layers of coarse, well-rounded pebbles included throughout this whole pile of strata, as well as of the great upper mass of conglomerate from 2,000 to 3,000 feet thick; for coarse gravel could hardly have been formed or spread out at the profound depths indicated by the thickness of the strata. The subsidence, also, must have been slow to have allowed of this often-recurrent spreading out of the pebbles. Moreover, we shall presently see that the surfaces of some of the streams of porphyritic lava beneath the gypseous formation, are so highly amygdaloidal that it is scarcely possible to believe that they flowed under the vast pressure of a deep ocean. The conclusion of a great subsidence during the existence of these cretaceo-oolitic fossils, may, I believe, be extended to the district of Coquimbo, although owing to the fossiliferous beds there not being directly covered by the upper gypseous strata, which in the section north of the valley are about 6,000 feet in thickness, I did not there insist on this conclusion.

The pebbles in the above conglomerates, both in the upper and lower beds, are all well rounded, and, though chiefly composed of various porphyries, there are some of red sandstone and of a jaspery stone, both like the rocks intercalated in layers in this same gypseous formation; there was one pebble of mica-slate and some of quartz, together with many particles of quartz. In these respects there is a wide difference between the gypseous conglomerates and those of the porphyritic-conglomerate formation, in which latter, angular and rounded fragments, almost exclusively composed of porphyries, are mingled together, and which, as already often remarked, probably were ejected from craters deep under the sea. From these facts I conclude, that during the formation of the conglomerates, land existed in the neighbourhood, on the shores of which the innumerable pebbles were rounded and thence dispersed, and on which the coniferous forests flourished—for it is improbable that so many thousand logs of wood should have drifted from any great distance. This land, probably islands, must have been mainly formed of porphyries, with some mica-slate, whence the quartz was derived, and with some red sandstone and jaspery rocks. This latter fact is important, as it shows that in this district, even previously to the deposition of the lower gypseous or cretaceo-oolitic beds, strata of an analogous nature had elsewhere, no doubt in the more central ranges of the Cordillera, been elevated; thus recalling to our minds the relations of the Cumbre and Uspallata chains. Having already referred to the great lateral valley of the Despoblado, I may mention that above the 2,700 feet of red and white sandstone and dark mudstone, there is a vast mass of coarse, hard, red conglomerate, some thousand feet in thickness, which contains much silicified wood, and evidently corresponds with the great upper conglomerate at Las Amolanas: here, however, the conglomerate consists almost exclusively of pebbles of granite, and of disintegrated crystals of reddish feldspar and quartz firmly recemented together. In this case, we may conclude that the land whence the pebbles were derived, and on which the now silicified trees once flourished, was formed of granite.

The mountains near Las Amolanas, composed of the cretaceo-oolitic strata, are interlaced with dikes like a spider’s web, to an extent which I have never seen equalled, except in the denuded interior of a volcanic crater: north and south lines, however, predominate. These dikes are composed of green, white, and blackish rocks, all porphyritic with feldspar, and often with large crystals of hornblende. The white varieties approach closely in character to andesite, which composes as we have seen, the injected axes of so many of the lines of elevation. Some of the green varieties are finely laminated, parallel to the walls of the dikes.

_Sixth axis of elevation (Valley of Copiapo)._—This axis consists of a broad mountainous mass [O] of andesite, composed of albite, brown mica, and chlorite, passing into andesitic granite, with quartz: on its western side it has thrown off, at a considerable angle, a thick mass of stratified porphyries, including much epidote [NN], and remarkable only from being divided into very thin beds, as highly amygdaloidal on their surfaces as subaerial lava-streams are often vesicular. This porphyritic formation is conformably covered, as seen some way up the ravine of Jolquera, by a mere remnant of the lower part of the cretaceo-oolitic formation [MM], which in one part encases, as represented in the coloured section, the foot of the andesitic axis [L], of the already described fifth line, and in another part entirely conceals it: in this latter case, the gypseous or cretaceo-oolitic strata falsely appeared to dip under the porphyritic conglomerate of the fifth axis. The lowest bed of the gypseous formation, as seen here [M], is of yellowish siliceous sandstone, precisely like that of Amolanas, interlaced in parts with veins of gypsum, and including layers of the black, calcareous, non-fissile slate-rock: the _ Turritella Andii, Pecten Dufreynoyi, Terebratula ænigma, var.,_ and some Gryphites were embedded in these layers. The sandstone varies in thickness from only twenty to eighty feet; and this variation is caused by the inequalities in the upper surface of an underlying stream of purple claystone porphyry. Hence the above fossils here lie at the very base of the gypseous or cretaceo-oolitic formation, and hence they were probably once covered up by strata about seven thousand feet in thickness: it is, however, possible, though from the nature of all the other sections in this district not probable, that the porphyritic claystone lava may in this case have invaded a higher level in the series. Above the sandstone there is a considerable mass of much indurated, purplish-black, calcareous claystone, allied in nature to the often-mentioned black calcareous slate-rock.

Eastward of the broad andesitic axis of this sixth line, and penetrated by many dikes from it, there is a great formation [P] of mica-schist, with its usual variations, and passing in one part into a ferruginous quartz-rock. The folia are curved and highly inclined, generally dipping eastward. It is probable that this mica-schist is an old formation, connected with the granitic rocks and metamorphic schists near the coast; and that the one fragment of mica-slate, and the pebbles of quartz low down in the gypseous formation at Las Amolanas, have been derived from it. The mica-schist is succeeded by stratified porphyritic conglomerate [Q] of great thickness, dipping eastward with a high inclination: I have included this latter mountain-mass in the same anticlinal axis with the porphyritic streams [NN]; but I am far from sure that the two masses may not have been independently upheaved.

_Seventh axis of elevation._—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 ænigma, 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;[4] 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.

[4] I have endeavoured to show in my “Journal,” etc. (2nd edit.), p. 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.

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;[5] 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.

[5] 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.

No. 40

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 no. 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° 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°: so that at this point the beds have been turned through an angle of 135°; and here there is a kind of anticlinal axis, with the strata on both sides dipping to opposite points at an angle of 45°, 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.[6] 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,[7]consists of laminated, impure, argillaceous, purplish-grey limestone, associated, I believe, with some purple sandstone. In the limestone shells are found: the three following species were given me:—

Lucina Americana, E. Forbes. Terebratula inca, E. Forbes. Terebratula ænigma, D’Orbigny.

[6] The lowest point, where the road crosses the coast-escarpment, is 1,900 feet by the barometer above the level of the sea.

[7] Mr. Bollaert has described (“Geolog. Proceedings,” vol. ii, p. 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.

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.[8] 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.

[8] 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’s “Anniversary Address to Geolog. Soc., 1843,” p. 65.)

_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.];[9] 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 laminæ 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.[10] 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[11] 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. 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.

[9] 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.].

[10] The same fact has been observed by Mr. Taylor in Cuba: _London Phil. Journ.,_ vol. xi, p. 21.

[11] “Travels in Chile,” p. 29.

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,[12] 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.

[12] 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.

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.[13] 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.

[13] Sir R. Murchison and his fellow travellers have given some striking facts on this subject in their account of the Ural Mountains (“Geolog. Proc.,” vol. iii, p. 748.

_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 palæontologists 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,[14] 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 ænigma,_ 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.

[14] Von Buch’s “Descript. Physique des Iles Canaries,” p. 428.

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.[15] 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.

[15] Sir R. Murchison and his companions state (“Geolog. Proc.,” vol. iii, p. 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.

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[16] as in volcanic archipelagoes lavas are contemporaneously ejected on the parallel lines of fissure. 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.[17] 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[18] 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.

[16] “Volcanic Islands,” etc.)

[17] I have endeavoured to show in my “Journal” (2nd edit., p. 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 Phil. Journal,_ vol. xxviii, pp. 33 and 44.

[18] “Reise in Peru,” Band 2, s. 8: Author’s “Journal,” 2nd edit., p. 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,[19] 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.

[19] “The Structure, etc., 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,[20] appears to me highly important, for no explanation of the one phenomenon can be considered as satisfactory which is not applicable to the other. 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.

[20] On the Connection of certain Volcanic Phenomena in South America: “Geolog. Transact.,” vol. v, p. 609.

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,[21] 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. 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.

[21] “Geolog. Transact.,” vol. v, p. 626.

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-Gürtelthiere in den Dünenhügeln bei Bahia Blanca, beides in Patagonien, unveränderte brakische Süsswasserbildungen sind, die einst wohl sämmtlich zum obersten Fluthgebiethe des Meeres im tieferen Festlande gehörten.”—_Monatsberichten der königl. Akad., etc.,_ zu Berlin vom April 1845.

INDEX TO CORAL-REEFS.

The names in italics are all names of places, and refer exclusively to the Appendix: in well-defined archipelagoes, or groups of islands, the name of each separate island is not given.

Abrolhos, Brazil, coated by corals 50 _Abrolhos (Australia)_ 130 Absence of coral-reefs from certain coasts 51 _Acaba, gulf of_ 147 _Admiralty group_ 124 Africa, east coast, fringing-reef of 48 —— Madreporitic rock of 101 _Africa, east coast_ 141 Age of individual corals 57, 64 _Aiou_ 128 _Aitutaki_ 114 _Aldabra_ 139 _Alert reef_ 123 _Alexander, Grand Duke, island_ 115 Allan, Dr., on Holuthuriæ feeding on corals 21 —— on quick growth of corals at Madagascar 62 —— on reefs affected by currents 9 _Alloufatou_ 119 _Alphonse_ 139 _Amargoura (Amargura)_ 119 _Amboina_ 128 _America, west coast_ 111 _Amirantes_ 138 _Anachorites_ 125 _Anambas_ 133 Anamouka, description of 99 _Anamouka_ 119 _Anadaman islands_ 132 _Antilles_ 153 _Appoo reef_ 134 _Arabia Felix_ 143 Areas, great extent of, interspersed with low islands —— of subsidence and of elevation 106 —— of subsidence appear to be elongated 106 —— of subsidence alternating with areas of elevation 108 _Arru group_ 128 _Arzobispo_ 127 Ascidia, depth at which found 67 _Assomption_ 139 _Astova_ 139 _Atlantic islands_ 121 Atolls, breaches in their reefs 31, 81 —— dimensions of 25 —— dimensions of groups of 71 —— not based on craters or on banks of sediment, or of ck 69, 71, 72, 73, 108 —— of irregular forms 25, 84 —— steepness of their flanks 26 —— width of their reef and islets 25 —— their lowness 70 —— lagoons 29 —— general range 94 —— with part of their reef submerged, and theory of 29, 81 _Augustine, St._ 120 Aurora island, an upraised atoll 64, 71, 104 _Aurora_ 112 Austral islands, recently elevated 99 _Austral islands_ 114 _Australia, N.W. coast_ 130 Australian barrier-reef 42, 93 _Australian barrier_ 123

_Babuyan group_ 134 _Bahama banks_ 149, 150 _Balahac_ 133 _Bally_ 131 _Baring_ 121 Barrier-reef of Australia 42, 93 —— of New Caledonia 44 Barrier-reefs, breaches through 77 —— not based on worn down margin of rock 43 —— on banks of sediment 43 —— on submarine craters 44 —— steepness of their flanks 39 —— their probable vertical thickness 43, 76 —— theory of their formation 76, 78 _Bampton shoal_ 123 _Banks islands_ 122 _Banks in the West Indies_ 147 _Bashee islands_ 134 _Bass island_ 115 _Batoa_ 119 _Beaupré reef_ 123 Beechey, Captain, obligations of the author to 26 —— on submerged reefs 27 —— account of Matilda island 60 Belcher, Captain, on boring through coral-reef 59 _Belize reef, off_ 151 _Bellinghausen_ 113 _Bermuda islands_ 153 _Beveridge reef_ 118 _Bligh_ 122 Bolabola, view of 12 _Bombay shoal_ 136 _Bonin Bay_ 131 _Bonin group_ 127 Borings through coral-reefs 59 Borneo, W. coast, recently elevated 101 _Borneo, E. coast_ 131 —— _S.W. and W. coast_ 133 —— _N. coast_ 133 —— _western bank_ 136 _Boscawen_ 119 _Boston_ 121 _Bouka_ 124 _Bourbon_ 138 _Bourou_ 128 _Bouton_ 132 Brazil, fringing-reefs on coast of 48 Breaches through barrier-reefs 71 _Brook_ 115 _Bunker_ 115 _Bunoa_ 133 Byron 121

_Cagayanes_ 133 _Candelaria_ 124 _Cargados Carajos_ 138 _Caroline archipelago_ 125 _Caroline island_ 115 _Carteret shoal_ 128 Caryophyllia, depth at which it lives 66 _Cavilli_ 133 _Cayman island_ 152 _Celebes_ 129 _Ceram_ 128 Ceylon, recently elevated 101 _Ceylon_ 137 Chagos Great Bank, description and theory of 37, 85 Chagos group 86 _Chagos group_ 137 Chama-shells embedded in coral-rock 68 Chamisso, on corals preferring the surf 52 Changes in the state of Keeling atoll 21 —— of atolls 74 Channels leading into the lagoons of atolls 30, 82 —— —— into the Maldiva atolls 33, 35 —— through barrier-reefs 77 _Chase_ 120 _China sea_ 135 Christmas atoll 60, 97 _Christmas atoll_ 116 _Christmas island_ (Indian Ocean) 137 _Clarence_ 116 _Clipperton rock_ 111 Cocos, or Keeling atoll 15 _Cocos (or Keeling)_ 137 _Cocos island_ (Pacific) 111 Cochin China, encroachments of the sea on the coast 95 _Cochin China_ 183 _Coetivi_ 139 _Comoro group_ 139 Composition of coral-formations 88 Conglomerate coral-rock on Keeling atoll 20 —— on other atolls 28 —— coral-rock 88 Cook islands, recently elevated 98, 103 _Cook islands_ 114 Coral-blocks bored by vermiform animals 21, 88 Coral-reefs, their distribution and absence from certain areas 50 —— destroyed by loose sediment 53 Coral-rock at Keeling atoll 20 —— Mauritius 47 —— organic remains of 88 Corals dead but upright in Keeling lagoon 22 —— depths at which they live 64 —— off Keeling atoll 17 —— killed by a short exposure 16 —— living in the lagoon of Keeling atoll 20 —— quick growth of, in Keeling lagoon 21 —— merely coating the bottom of the sea 50 —— standing exposed in the Low archipelago 96 Corallian sea 94 _Corallian sea_ 123 _Cornwallis_ 121 _Cosmoledo_ 139 Couthouy, Mr., alleged proofs of recent elevation of the Low archipelago 96 —— on coral-rock at Mangaia and Aurora islands 64 —— on external ledges round coral-islands 80 —— remarks confirmatory of the author’s theory 96 Crescent-formed reefs 84 _Cuba_ 150 Cuming, Mr., on the recent elevation of the Philippines 101

_Dangerous, or Low archipelago_ 111 _Danger islands_ 116 Depths at which reef-building corals live 63 —— at Mauritius, the Red Sea, and in the Maldiva archipelago 66 —— at which other corals and corallines can live 67 _Dhalac group_ 144 Diego Garcia, slow growth of reef 56 Dimensions of the larger groups of atolls 71 Disseverment of the Maldiva atolls, and theory of 37, 82 Distribution of coral-reefs 50 _Domingo, St._ 152 Dory, Port, recently elevated 100 _Dory, Port_ 127 _Duff islands_ 122 _Durour_ 125

_Eap_ 126 arthquakes at Keeling atoll 23 —— in groups of atolls 75 —— in Navigator archipelago 100 ast Indian archipelago, recently elevated 100 _Easter_ 111 _Echequier_ 125 hrenberg, on the banks of the Red Sea 49, 143 —— on depths at which corals live in the Red Sea 66 —— on corals preferring the surf 53 —— on the antiquity of certain corals 57 _Eimeo_ 112 levated reef of Mauritius 47 levations, recent proofs of 98 —— immense areas of 106 _Elivi_ 126 lizabeth island 59 —— recently elevated 98, 104 _Elizabeth island_ 112 _Ellice group_ 120 ncircled islands, their height 41 —— geological composition 42, 44 ua, description of 99 _Eoua_ 118 upted matter probably not associated with thick masses of coral-rock 89

Fais, recently elevated 100, 104 _Fais_ 126 _Fanning_ 116 _Farallon de Medinilla_ 127 _Farson group_ 144 _Fataka_ 122 Fiji archipelago 119 Fish, feeding on corals 21 —— killed in Keeling lagoon by heavy rain 24 Fissures across coral-islands 75 Fitzroy, Captain, on a submerged shed at Keeling atoll 23 —— on an inundation in the Low archipelago 74 _Flint_ 115 _Flores_ 130 _Florida_ 149 _Folger_ 127 _Formosa_ 135 Forster, theory of coral-formations 73 _Frederick reef_ 123 _Freewill_ 128 Friendly group recently elevated 99, 105 _Friendly archipelago_ 118 Fringing-reefs, absent where coast precipitous 5 —— breached in front of streams 54 —— described by MM. Quoy and Gaimard 98 —— not closely attached to shelving coasts 46 —— of east coast of Africa —— of Cuba 48 —— of Mauritius 45 —— on worn down banks of rock 9 —— on banks of sediment 49 —— their appearance when elevated 7 —— their growth influenced by currents 49 —— by shallowness of sea 49

_Galapagos archipelago_ 111 _Galega_ 139 Gambier islands, section of 43 _Gambier islands_ 112 _Gardner_ 116 _Gaspar rico_ 121 Geological composition of coral-formations

_Gilbert archipelago_ 120 _Gilolo_ 129 _Glorioso_ 139 Gloucester island 74 _Glover reef_ 152 _Gomez_ 111 _Gouap_ 126 _Goulou_ 126 _Grampus_ 127 _Gran Cocal_ 120 Great Chagos Bank, description and theory of 37, 85 Grey, Captain, on sandbars 46 Grouping of the different classes of reefs 93 _Guedes_ 128

Hall, Captain B., on Loo Choo 101 Harvey islands, recently elevated 104 Height of encircled islands 41 _Hermites_ 125 _Hervey or Cook islands_ 114 _Hogoleu_ 125 Holothuriæ (Holuthuriæ) feeding on coral 21 Houden island, height of 71 _Honduras, reef off_ 151 _Horn_ 119 _Houtman Abrolhos_ 130 Huaheine; alleged proofs of its recent elevation 103 _Huaheine_ 113 _Humphrey_ 115 _Hunter_ 119 Hurricanes, effects of, on coral-islands 74

_Immaum_ 143 _Independence_ 120 India, west coast, recently elevated 101 _India_ 143 Irregular reefs in shallow seas 49 Islets of coral-rock, their formation 19 —— their destruction in the Maldiva atolls 36

_Jamaica_ 152 _Jarvis_ 115 Java, recently elevated 100 _Java_ 131 _Johnston island_ 116 _Juan de Nova_ 139 _Juan de Nova (Madagascar)_ 140

_Kalatoa_ 131 Kamtschatka, proofs of its recent elevation 105 _Karkalang_ 129 Keeling atoll, section of reef 15 _Keeling, south atoll_ 137 —— _north atoll_ 137 _Keffing_ 128 _Kemin_ 115, 116 _Kennedy_ 123 _Keppel_ 119 _Kumi_ 135

_Laccadive group_ 137 Ladrones, or Marianas, recently elevated 100 _Ladrones archipelago_ 127 Lagoon of Keeling atoll 20 Lagoons bordered by inclined ledges and walls, and theory of their formation 32, 79 —— of small atolls filled up with sediment 32 Lagoon-channels within barrier-reefs 40 Lagoon-reefs, all submerged in some atolls, and rising to the surface in others 55 _Lancaster reef_ 115 _Latte_ 119 _Lauglan islands_ 123 Ledges round certain lagoons 32, 79 _Lette_ 129 _Lighthouse reef_ 152 Lloyd, Mr., on corals refixing themselves 62 Loo Choo, recently elevated 101 _Loo Choo_ 135 _Louisiade_ 123 Low archipelago, alleged proofs of its recent elevation 96 _Low archipelago_ 111 Lowness of coral-islands 70 _Loyalty group_ 123 _Lucepara_ 133 Lutké, Admiral, on fissures across coral-islands 75 Luzon, recently elevated 101 _Luzon_ 134 Lyell, Mr., on channels into the lagoons of atolls 31 —— on the lowness of their leeward sides 82 —— on the antiquity of certain corals 58 —— on the apparent continuity of distinct coral-islands 89 —— on the recently elevated beds of the Red Sea 102 —— on the outline of the areas of subsidence 106

_Macassar strait_ 131 _Macclesfield bank_ 136 Madagascar, quick growth of corals at 62 —— madreporitic rock of 101 _Madagascar_ 140 _Madjiko-sima_ 135 _Madura (Java)_ 131 _Madura (India)_ 137 Mahlos Mahdoo, theory of formation 88 Malacca, recently elevated 100 _Malacca_ 133 Malcolmson, Dr., on recent elevation of W. coast of India 100 —— on recent elevation of Camaran island 102 _Malden_ 115 Maldiva atolls, and theory of their formation 33, 80, 82 —— steepness of their flanks 26 —— growth of coral at 62 _Maldiva archipelago_ 137 Mangaia island 64 —— recently elevated 99, 104 _Mangaia_ 114 _Mangs_ 127 Marianas, recently elevated 100 _Mariana archipelago_ 127 _Mariere_ 126 _Marquesas archipelago_ 113 _Marshall archipelago_ 121 _Marshall island_ 127 _Martinique_ 153 _Martires_ 126 Mary’s St. in Madagascar, harbour made in reefs 54 _Mary island_ 116 _Matia, or Aurora_ 112 Matilda atoll 60 Mauritius, fringing-reefs of 45 —— depths at which corals live there 64 —— recently elevated 101 _Mauritius_ 138 Maurua, section of 43 _Maurua_ 113 Menchikoff atoll 25,

_Mendana archipelago_ 113 _Mendana isles_ 122 _Mexico, gulf of_ 149 Millepora complanata at Keeling atoll 16 _Mindoro_ 134 _Mohilla (Mohila)_ 139 Molucca islands, recently elevated 100 _Mopeha_ 113 Moresby, Captain, on boring through coral-reefs 59 _Morty_ 129 _Mosquito coast_ 152 Musquillo atoll 84 _Mysol_ 129

Namourrek group 84 _Natunas_ 133 Navigator archipelago, elevation of 99 _Navigator archipelago_ 117 _Nederlandisch_ 120 Nelson, Lieutenant, on the consolidation of coral-rocks under water 59 —— theory of coral-formations 73 —— on the Bermuda islands 154 _New Britain_ 124 New Caledonia, steepness of its reefs 39 —— —— barrier-reef of , 79, 83, 93 _New Caledonia_ 123 _New Guinea (E. end)_ 124 _New Guinea (W. end)_ 127 _New Hanover_ 124 New Hebrides, recently elevated 100 _New Hebrides_ 121 New Ireland, recently elevated 100 _New Ireland_ 124 _New Nantucket_ 116 _Nicobar islands_ 132 _Niouha_ 119 Nulliporæ at Keeling atoll 18 —— on the reefs of atolls 28 —— on barrier-reefs 39 —— their wide distribution and abundance 68

Objections to the theory of subsidence 7 _Ocean islands_ 117, 121 _Ono_ 120 _Onouafu (Onouafou)_ 119 _Ormuz_ 143 _Oscar group_ 120 Oscillations of level 103, 108 _Ouallan, or Ualan (Oualan)_ 125 Ouluthy atoll 60 _Outong Java_ 124

_Palawan, S.W. coast 133 —— N.W. coast 134 —— western bank 136 _ Palmerston 114 _Palmyra_ 116 _Paracells_ 136 _Paraquas_ 136 _Patchow_ 135 _Pelew islands_ 126 Pemba island, singular form of 102 _Pemba_ 142 _Penrhyn_ 115 _Peregrino_ 115 Pernambuco, bar of sandstone at 47 Persian gulf, recently elevated 102 _Persian gulf_ 143 Pescado 115 _Pescadores_ 135 _Peyster group_ 120 _Philip_ 126 Philippine archipelago, recently elevated 101 _Philippine archipelago_ 134 _Phœnix_ 116 _Piguiram_ 126 _Pitcairn_ 112 Pitt’s bank 86 _Pitt island_ 120 _Platte_ 139 _Pleasant_ 121 Porites, chief coral on margin of Keeling atoll 16 _Postillions_ 131 Pouynipète 95 —— its probable subsidence 95 _Pouynipète_ 125 _Pratas shoal_ 135 _Proby_ 119 _Providence_ 139 _Puerto Rico_ 152 _Pulo Anna_ 126 Pumice floated to coral-islands 88 _Pylstaart_ 118 Pyrard de Laval, astonishment at the atolls in the Indian Ocean 11

Quoy and Gaimard, depths at which corals live 66 —— description of reefs applicable only to fringing-reefs 98

Range of atolls 94 _Rapa_ 115 _Rearson_ 115 Red Sea, banks of rock coated by reefs 49 —— proofs of its recent elevation 102 —— supposed subsidence of 103 _Red Sea_ 143 Reefs, irregular in shallow seas 49 —— rising to the surface in some lagoons and all submerged in others 55 —— their distribution 50 —— their absence from some coasts 51 _Revilla-gigedo_ 111 Ring-formed reefs of the Maldiva atolls, and theory of , 80 _Rodriguez_ 138 _Rosario_ 127 _Rose island_ 118 _Rotches_ 120 _Rotoumah_ 120 _Roug_ 125 _Rowley shoals_ 130 Rüppell, Dr., on the recent deposits of Red Sea 102

_Sable, ile de_ 138 _Sahia de Malha_ 137 _St. Pierre_ 139 _Sala_ 111 _Salomon (Solomon) archipelago_ 123 Samoa, or Navigator archipelago, elevation of 99 _Samoa archipelago_ 117 Sand-bars parallel to coasts 46 _Sandal-wood_ 129 Sandwich archipelago, recently elevated 98 _Sandwich archipelago_ 117 _Sanserot_ 126 _Santa-Cruz group_ 122 Savage island, recently elevated 59, 99, 104 _Savage_ 118 _Savu_ 129 _Saya, or Sahia de Malha_ 137 _Scarborough shoal_ 136 Scarus feeding on corals 21 _Schouten_ 124 _Scilly_ 113 Scoriæ floated to coral-islands 89 _Scott’s reef_ 130 Sections of islands encircled by barrier-reefs 43, 176 —— of Bolabola 76 Sediment in Keeling lagoon 21 —— in other atolls 29, 35 —— injurious to corals 53 —— transported from coral-islands far seaward 89 _Seniavine_ 125 _Serangani_ 129 _Seychelles_ 138 Ship-bottom quickly coated with coral 62 _Smyth island_ 116 Society archipelago, stationary condition of 96 —— alleged proofs of recent elevation 103 _Society archipelago_ 112 _Socotra_ 143 _Solor_ 130 Sooloo islands, recently elevated 101 _Sooloo islands_ 133 _Souvaroff_ 115 _Spanish_ 126 Sponge, depths at which found 67 _Starbuck (Slarbuck)_ 115 Stones transported in roots of trees 89 Storms, effects of, on coral-islands 74 Stutchbury, Mr., on the growth of an Agaricia 63 —— on upraised corals in Society archipelago 103 Subsidence of Keeling atoll 28 —— extreme slowness of 87, 108 —— areas of, apparently elongated 106 —— areas of immense 106 —— great amount of 108 _Suez, gulf of_ 147 _Sulphur islands_ 127 Sumatra, recently elevated 100 _Sumatra_ 132 _Sumbawa_ 130 Surf favourable to the growth of massive corals 52 _Swallow shoal_ 136 _Sydney island_ 116

Tahiti, alleged proofs of its recent elevation 103 _Tahiti_ 112 Temperature of the sea at the Galapagos archipelago 51 _Tenasserim_ 133 _Tenimber island_ 128 _Teturoa_ 113 Theories on coral-formations 69, 73 Theory of subsidence, and objections to 72, 86 Thickness, vertical, of barrier-reefs 43, 76 _Thomas, St._ 153 _Tikopia_ 122 Timor, recently elevated 100 _Timor_ 129 _Timor-laut_ 128 _Tokan-Bessees_ 131 _Tongatabou_ 118 _Tonquin_ 137 _Toubai_ 113 _Toufoa (Toofoa)_ 119 _Toupoua_ 122 Traditions of change in coral-islands 73 Tridacnæ embedded in coral-rock 63 —— left exposed in the Low archipelago 96 Tubularia, quick growth of 63 _Tumbelan_ 133 _Turneffe reef_ 152 _Turtle_ 119

_Ualan_ 125

Vanikoro, section of 43 —— its state and changes in its reefs 95 _Vanikoro_ 122 _Vine reef_ 125 _Virgin Gorda_ 153 _Viti archipelago_ 119 Volcanic islands, with living corals on their shores 51 —— matter, probably not associated with thick masses of coral-rock 88 Volcanoes, authorities for their position on the map 90 —— their presence determined by the movements in progress 104 —— absent or extinct in the areas of subsidence 105

_Waigiou_ 128 _Wallis island_ 119 _Washington_ 116 _Wells’ reef_ 123 Wellstead, Lieutenant, account of a ship coated with corals 62 West Indies, banks of sediment fringed by reefs 49 —— recently elevated 102 _West Indies_ 147 Whitsunday island, view of 12 —— changes in its state 74 Williams, Rev. J., on traditions of the natives regarding coral-islands 74 —— on antiquity of certain corals 64 _Wolchonsky_ 111 _Wostock_ 115

_Xulla islands_ 128

_York island_ 116 _Yucutan, coast of_ 151

Zones of different kinds of corals outside the same reefs 55, 60

INDEX TO VOLCANIC ISLANDS.

Abel, M., on calcareous casts at the Cape of Good Hope 261 Abingdon island 234 Abrolhos islands, incrustation on 188 Aeriform explosions at Ascension 191 _Albatross_, driven from St. Helena 225 Albemarle island 234 Albite, at the Galapagos archipelago 234 Amygdaloidal cells, half filled 184 Amygdaloids, calcareous origin of 176 Ascension, arborescent incrustation on rocks of 188 —— absence of dikes, freedom from volcanic action, and state of lava-streams 226 Ascidia, extinction of 258 Atlantic Ocean, new volcanic focus in 226 Augite, fused 239 Australia 251 Azores 182, 248

Bahia in Brazil, dikes at 247 Bailly, M., on the mountains of Mauritius 185 Bald Head 260 Banks’ Cove 234, 236 Barn, The, St. Helena 216 Basalt, specific gravity of 245 Basaltic coast-mountains at Mauritiu 185 —— at St. Helena 218 —— at St. Jago 178 Beaumont, M. Elie de, on circular subsidences in lava 233 —— on dikes indicating elevation 228 —— on inclination of lava-streams 227 —— on laminated dikes 212 Bermuda, calcareous rocks of 260, 262 Beudant, M., on bombs 191 —— on jasper 197 —— on laminated trachyte 211 —— on obsidian of Hungary 207 —— on silex in trachyte 270, 197 Bole 257 Bombs, volcanic 189 Bory St. Vincent, on bombs 190 Boulders, absence in Australia and Cape of Good Hope 265 Brattle island 238 Brewster, Sir D., on a calcareo-animal substance 201 —— on decomposed glass 252 Brown, Mr. R., on extinct plants from Van Diemen’s land 257 —— on sphærulitic bodies in silicified wood 207 Buch, Von, on cavernous lava 233 —— on central volcanoes 249 —— on crystals sinking in obsidian 243 —— on laminated lava 209 —— on obsidian streams 208 —— on olivine in basalt 234 —— on superficial calcareous beds in the Canary islands 224

Calcareous deposit at St. Jago affected by heat 169, 171 —— fibrous matter, entangled in streaks in scoriæ 174 —— freestone at Ascension 198 —— incrustations at Ascension 199 —— sandstone at St. Helena 222 —— superficial beds at King George’s sound 260 Cape of Good Hope 263 Carbonic acid, expulsion of, by heat 171, 176 Carmichael, Capt., on glassy coatings to dikes 216 Casts, calcareous, of branches 261 Chalcedonic nodules 257 Chalcedony in basalt and in silicified wood 196 Chatham island 231, 235, 241, 248, 259 Chlorophæite 257 Clarke, Rev. W., on the Cape of Good Hope 258, 263 Clay-slate, its decomposition and junction with granite at the Cape of Good Hope 264 Cleavage of clay-slate in Australia 252 Cleavage, cross, in sandstone 253 Coast denudation at St. Helena 226 Columnar basalt 173 “Comptes Rendus,” account of volcanic phenomena in the Atlantic 226 Concepcion, earthquake of 228, 249 Concretions in aqueous and igneous rocks compared 206 —— in tuff 197 —— of obsidian 206, 208 Conglomerate, recent, at St. Jago 181 Coquimbo, curious rock of 261 Corals, fossil, from Van Diemen’s Land 256 Crater, segment of, at the Galapagos 238 —— great central one at St. Helena 219 —— internal ledges round, and parapet on 220 Craters, basaltic, at Ascension 189 —— form of, affected by the trade wind 189 —— of elevation 227 —— of tuff at Terceira 182 —— of tuff at the Galapagos archipelago 230, 231, 235, 237 —— their breached state 240 —— small basaltic at St. Jago 177 —— —— at the Galapagos archipelago 232 Crystallisation favoured by space 211

Dartigues, M., on sphærulites 207 Daubeny, Dr., on a basin-formed island 237 —— on fragments in trachyte 193 D’Aubuisson on hills of phonolite 222 —— on the composition of obsidian 206 —— on the lamination of clay-slate 210 De la Beche, Sir H., on magnesia in erupted lime 174 —— on specific gravity of limestones 198 Denudation of coast at St. Helena 226 Diana’s Peak, St. Helena 220 Dieffenbach, Dr., on the Chatham Islands 259 Dikes, truncated, on central crateriform ridge of St. Helena 219 —— at St. Helena; number of; coated by a glossy layer; uniform thickness of 216 —— great parallel ones at St. Helena 222 —— not observed at Ascension 226 —— of tuff 231 —— of trap in the plutonic series 247 —— remnants of, extending far into the sea round St. Helena 226 Dislocations at Ascension 192 —— at St. Helena 217, 221 Distribution of volcanic islands 248 Dolomieu, on decomposed trachyte 182 —— on laminated lava 210, 211 —— on obsidian 208 Drée, M., on crystals sinking in lava 243 Dufrenoy, M., on the composition of the surface of certain lava-streams 209, 243 —— on the inclination of tuff-strata 236

Eggs of birds embedded at St. Helena 224 —— of turtle at Ascension 198 Ejected fragments at Ascension 192 —— at the Galapagos archipelago 239 Elevation of St. Helena 225 —— the Galapagos archipelago 241 —— Van Diemen’s Land, Cape of Good Hope, New Zealand, Australia, and Chatham island 258 —— of volcanic islands 250 Ellis, Rev. W., on ledges within the great crater at Hawaii 220 —— on marine remains at Otaheite 184 Eruption, fissures of 224, 249, 250 Extinction of land-shells at St. Helena 224

Faraday, Mr., on the expulsion of carbonic acid gas 171 Feldspar, fusibility of 246 —— in radiating crystals 263 —— Labrador, ejected 193 Feldspathic lavas 179 —— at St. Helena 219 —— rock, alternating with obsidian 202 —— lamination, and origin of 209 Fernando Noronha 181, 210 Ferruginous superficial beds 259 Fibrous calcareous matter at St. Jago 174 Fissures of eruption 242, 249, 250 Fitton, Dr., on calcareous breccia 262 Flagstaff Hill, St. Helena 216 Fleurian de Bellevue on sphærulites 207 Fluidity of lavas 234, 235 Forbes, Professor, on the structure of glaciers 212 Fragments ejected at Ascension 192 —— at the Galapagos archipelago 239 Freshwater Bay 238, 243 Fuerteventura (Feurteventura), calcareous beds of 224

Galapagos archipelago 229 —— parapets round craters 220 Gay Lussac, on the expulsion of carbonic acid gas 171 Glaciers, their structure 212 Glossiness of texture, origin of 206 Gneiss, derived from clay-slate 264 —— with a great embedded fragment 252 Gneiss-granite, form of hills of 259 Good Hope, Cape of 263 Gorges, narrow, at St. Helena 225 Granite, junction with clay-slate, at the Cape of Good Hope 263 Granitic ejected fragments 192, 239 Gravity, specific, of lavas 243-8 Gypsum, at Ascension 201 —— in volcanic strata at St. Helena 215 —— on surface of the ground at ditto 223

Hall, Sir J., on the expulsion of carbonic acid gas 171 Heat, action of, on calcareous matter 170 Hennah, Mr., on ashes at Ascension 189 Henslow, Prof., on chalcedony 197 Hoffmann, on decomposed trachyte 182 Holland, Dr., on Iceland 228 Horner, Mr., on a calcareo-animal substance 201 —— on fusibility of feldspar 246 Hubbard, Dr., on dikes 247 Humboldt on ejected fragments 193 —— on obsidian formations 207, 209 —— on parapets round craters 220 —— on sphærulites 210 Hutton on amygdaloids 176 Hyalite in decomposed trachyte 182

Iceland, stratification of the circumferential hills 228 Islands, volcanic, distribution of 248 —— their elevation 250 Incrustation, on St. Paul’s rocks 187 Incrustations, calcareous, at Ascension 199

Jago, St. 167 James island 234, 237, 242 Jasper, origin of 196 Jonnès, M. Moreau de, on craters affected by wind 189 Juan Fernandez 250

Keilhau, M., on granite 264 Kicker Rock 232 King George’s sound 259

Labrador feldspar, ejected 193 Lakes at bases of volcanoes 229 Lamination of volcanic rocks 209 Land-shells, extinct, at St. Helena 224 Lanzarote, calcareous beds of 223 Lava, adhesion to sides of a gorge 177 —— feldspathic 179 —— with cells semi-amygdaloidal 184 Lavas, specific gravity of 243, 247 Lava-streams blending together at St. Jago 177 —— composition of surface of 208 —— differences in the state of their surfaces 244 —— extreme thinness of 238 —— heaved up into hillocks at the Galapagos archipelago 233 —— their fluidity 234, 235 —— with irregular hummocks at Ascension 189 Lead, separation from silver 244 Lesson, M., on craters at Ascension 189 Leucite 234 Lime, sulphate of, at Ascension 200 Lonsdale, Mr., on fossil-corals from Van Diemen’s land 256 Lot, St. Helena 221 Lyell, Mr., on craters of elevation 227 —— on embedded turtles’ eggs 198 —— on glossy coating to dikes 216

Macaulay, Dr., on calcareous casts at Madeira 262 MacCulloch, Dr., on an amygdaloid 184 —— on chlorophæite 287 —— on laminated pitchstone 209 Mackenzie, Sir G., on cavernous lava-streams 233 —— on glossy coatings to dikes 216 —— on obsidian streams 208 —— on stratification in Iceland 228 Madeira, calcareous casts at 262 _Magazine, Nautical,_—account of volcanic phenomena in the Atlantic 226 Marekanite 206 Mauritius, crater of elevation of 184, 227 Mica, in rounded nodules 168 —— origin in metamorphic slate 264 —— radiating form of 263 Miller, Prof., on ejected Labrador feldspar 193 —— on quartz crystals in obsidian beds 202 Mitchell, Sir T., on bombs 191 —— on the Australian valleys 254 Mud streams at the Galapagos archipelago 236

Narborough island 234 Nelson, Lieut., on the Bermuda islands 260, 262 New Caledonia 248 New Red sandstone, cross cleavage of 253 New South Wales 251 New Zealand 259 Nulliporæ (fossil), resembling concretions 169

Obsidian, absent at the Galapagos archipelago 241 —— bombs of 191 —— composition and origin of 207, 208 —— crystals of feldspar sink in 243 —— its irruption from lofty craters 246 —— passage of beds into 202 —— specific gravity of 243, 246 —— streams of 208 Olivine decomposed at St. Jago 178 —— at Van Diemen’s land 257 —— in the lavas at the Galapagos archipelago 234 Oolitic structure of recent calcareous beds at St. Helena 223 Otaheite 183 Oysters, extinction of 258

Panza islands, laminated trachyte of 209 Pattinson, Mr., on the separation of lead and silver 244 Paul’s, St., rocks of 187 Pearlstone 206 Peperino 232 Péron, M., on calcareous rocks of Australia 262, 263 Phonolite, hills of 179, 181, 221 —— laminated 210 —— with more fusible hornblende 246 Pitchstone 204 —— dikes of 209 Plants, extinct 257 Plutonic rocks, separation of constituent parts of, by gravity 246 Porto Praya 167 Prevost, M. C., on rarity of great dislocations in volcanic islands 217 Prosperous hill, St. Helena 218 Pumice, absent at the Galapagos archipelago 241 —— laminated 209, 210, 211 Puy de Dome, trachyte of 193

Quail island, St. Jago 168, 170, 173 Quartz, crystals of, in beds alternating with obsidian 202 —— crystallised in sandstone 252 —— fusibility of 246 —— rock, mottled from metamorphic action with earthy matter 170

Red hill 173 Resin-like altered scoriæ 171 Rio de Janeiro, gneiss of 252 Robert, M., on strata of Iceland 228 Rogers, Professor, on curved lines of elevation 249

Salses, compared with tuff craters 240 Salt deposited by the sea 200 —— in volcanic strata 201, 215 —— lakes of, in craters 240 Sandstone of Brazil 265 —— of the Cape of Good Hope 265 —— platforms of, in New South Wales 252, 265 Schorl, radiating 263 Scrope, Mr. P., on laminated trachyte 209, 210, 212 —— on obsidian 208 —— on separation of trachyte and basalt 244 —— on silex in trachyte 176 —— on sphærulites 210 Seale, Mr., geognosy of St. Helena 215 —— on dikes 226 —— on embedded birds’ bones 225 Seale, on extinct shells of St. Helena 224 Sedgwick, Professor, on concretions 206 Septaria, in concretions in tuff 198 Serpulæ on upraised rocks 185 Seychelles 248 Shells, colour of, affected by light 201 —— from Van Diemen’s land 256 —— land, extinct, at St. Helena 224 —— particles of, drifted by the wind at St. Helena 223 Shelly matter deposited by the waves 200 Siau, M., on ripples 254 Signal Post Hill 168, 175, 176 Silica, deposited by steam 182 —— large proportion of, in obsidian 206, 208 —— specific gravity of 246 Siliceous sinter 196 Smith, Dr. A., on junction of granite and clay-slate 264 Spallanzani on decomposed trachyte 182 Specific gravity of recent calcareous rocks and of limestone 198 —— of lavas 245 Sphærulites in glass and in silicified wood 207 —— in obsidian 204, 210 Sowerby, Mr. G. B., on fossil-shells from Van Diemen’s land 256 —— from St. Jago 169 —— land-shells from St. Helena 224 St. Helena 214 —— crater of elevation of 227 St. Jago, crater of elevation of 227 —— effects of calcareous matter on lava 231 St. Paul’s rocks 187, 248 Stokes, Mr., collections of sphærulites and of obsidians 207, 212 Stony-top, Little 218, 222 —— Great 218 Stratification of sandstone in New South Wales 253, 255 Streams of obsidian 208 Stutchbury, Mr., on marine remains at Otaheite 184 Subsided space at Ascension 192

Tahiti 183 Talus, stratified, within tuff craters 236 Terceira 182 Tertiary deposit of St. Jago 169 Trachyte, absent at the Galapagos archipelago 241 —— at Ascension 193 —— at Terceira 182 —— decomposition of, by steam 182 —— its lamination 200, 210 —— its separation from basalt 244 —— softened at Ascension 194 —— specific gravity of 245 —— with singular veins 195 Trap-dikes in the plutonic series 247 —— at King George’s sound 259 Travertin at Van Diemen’s land 257 Tropic-bird, now rare, at St. Helena 225 Tuff, craters of 231, 235, 236 —— their breached state 240 —— peculiar kind of 231 Turner, Mr., on the separation of molten metals 244 Tyerman and Bennett on marine remains at Huaheine 184

Valleys, gorge-like, at St. Helena 225 —— in New South Wales 254 —— in St. Jago 180 Van Diemen’s land 256 Veins in trachyte 195 —— of jasper 195 Vincent, Bory St., on bombs 190 Volcanic bombs 189 —— island in process of formation in the Atlantic 226 —— islands, their distribution 248

Wacke, its passage into lava 183, 257 Wackes, argillaceous 168, 178 Webster, Dr., on a basin-formed island 237 —— on gypsum at Ascension 201 White, Martin, on soundings 254 Wind, effects of, on the form of craters

INDEX TO SOUTH AMERICAN GEOLOGY.

Abich, on a new variety of feldspar 446 Abrolhos islands 415 Absence of recent formations on the S. American coasts 409 Aguerros on elevation of Imperial 305 Albite, constituent mineral in andesite 446 —— in rocks of Tierra del Fuego 427 —— in porphyries 444 —— crystals of, with orthite 447 Alison, Mr., on elevation of Valparaiso 307, 310 Alumina, sulphate of 439 Ammonites from Concepcion 400, 405 Amolanas, Las 493 Amygdaloid, curious varieties of 444 Amygdaloids of the Uspallata range 471 —— of Copiapo 498 Andesite of Chile 446 —— in the valley of Maypu 449, 450 —— of the Cumbre pass 460, 466 —— of the Uspallata range 475 —— of Los Hornos 480 —— of Copiapo 488, 491 Anhydrite, concretions of 450, 463 Araucaria, silicified wood of 394, 474 Arica, elevation of 323 Arqueros, mines of 481 Ascension, gypsum deposited on 328 —— laminated volcanic rocks of 439, 440 Augite in fragments, in gneiss 414 —— with albite, in lava 347 Austin, Mr. R. A. C., on bent cleavage lamina 434 Austin, Captain, on sea-bottom 302 Australia, foliated rocks of 438 _Azara labiata_, beds of, at San Pedro 277, 352

_Baculites vagina_ 400 Bahia Blanca, elevation of 280 —— formations near 355 —— character of living shells of 408 Bahia (Brazil), elevation near 280 —— crystalline rocks of 414 Ballard, M., on the precipitation of sulphate of soda 349 Banda Oriental, tertiary formations of 365 —— crystalline rocks of 418 Barnacles above sea-level 311 —— adhering to upraised shells 306 Basalt of S. Cruz 389 —— streams of, in the Portillo range 456 —— in the Uspallata range 472 Basin chains of Chile 333 Beagle Channel 427, 430 Beaumont, Elie de, on inclination of lava-streams 390, 457 —— on viscid quartz-rocks 475 Beech-tree, leaves of fossil 391 Beechey, Captain, on sea-bottom 299 Belcher, Lieutenant, on elevated shells from Concepcion 306 Bella Vista, plain of 325 Benza, Dr., on decomposed granite 417 Bettington, Mr., on quadrupeds transported by rivers 374 Blake, Mr., on the decay of elevated shells near Iquique 322 —— on nitrate of soda 346 Bole 444 Bollaert, Mr., on mines of Iquique 503 Bones, silicified 402 —— fossil, fresh condition of 366 Bottom of sea off Patagonia 292, 298 Bougainville, on elevation of the Falkland islands 290 Boulder formation of S. Cruz 285, 295 —— of Falkland islands 290 —— anterior to certain extinct quadrupeds 371 —— of Tierra del Fuego 391 Boulders in the Cordillera 339, 341 —— transported by earthquake-waves 344 —— in fine-grained tertiary deposits 401 Brande, Mr., on a mineral spring 461 Bravais, M., on elevation of Scandinavia 320 Brazil, elevation of 279 —— crystalline rocks of 414, 418 Broderip, Mr., on elevated shells from Concepcion 306 Brown, Mr. R., on silicified wood of Uspallata range 474 Brown, on silicified wood 495 Bucalema, elevated shells near 307 Buch, Von, on cleavage 438 —— on cretaceous fossils of the Cordillera 453, 465 —— on the sulphureous volcanoes of Java 509 Buenos Ayres 352 Burchell, Mr., on elevated shells of Brazil 279 Byron, on elevated shells 303

Cachapual, boulders in valley of 339, 341 Caldcleugh, Mr., on elevation of Coquimbo 314 —— on rocks of the Portillo range 456 Callao, elevation near 323 —— old town of 327 Cape of Good Hope, metamorphic rocks of 439 _Carcharias megalodon_ 402 Carpenter, Dr., on microscopic organisms 352 Castro (Chiloe), beds near 394 Cauquenes Baths, boulders near 339, 341 —— pebbles in porphyry near 443 —— volcanic formation near 447 —— stratification near 449 Caves above sea-level 303, 307, 322 _Cervus pumilus,_ fossil-horns of 304 Chevalier, M., on elevation near Lima 323 Chile, structure of country between the Cordillera and the Pacific 333 —— tertiary formations of 337 —— crystalline rocks in 435 —— central, geology of 441 —— northern, geology of 479 Chiloe, gravel on coast 294 —— elevation of 303 —— tertiary formation of 337, 405 —— crystalline rocks of 433 Chlorite-schist, near M. Video 419 Chonos archipelago, tertiary formations of 393 —— crystalline rocks of 430 Chupat, Rio, scoriæ transported by 280 Claro, Rio, fossiliferous beds of 485 Clay-shale of Los Hornos 480 Clay-slate, formation of, Tierra del Fuego 424 —— of Concepcion 433 —— feldspathic, of Chile 442, 444, 448 —— —— of the Uspallata range 468, 470 —— black siliceous, band of, in porphyritic formations of Chile 445 Claystone porphyry, formation of, in Chile 442 —— origin of 445 —— eruptive sources of 444 Cleavage, definition of 414 —— at Bahia 415 —— Rio de Janeiro 415 —— Maldonado 418 —— Monte Video 420 —— S. Guitru-gueyu 421 —— Falkland I. 424 —— Tierra del Fuego 428 —— Chonos I. 434 —— Chiloe 435 —— Concepcion 434 —— Chile 435 —— discussion on 436 Cleavage-laminæ superficially bent 434 Cliffs, formation of 301 Climate, late changes in 345 —— of Chile during tertiary period 408 Coal of Concepcion 399 —— S. Lorenzo 504 Coast-denudation of St. Helena 301 Cobija, elevation of 322 Colombia, cretaceous formation of 504 Colonia del Sacramiento, elevation of 278 —— Pampean formation near 355 Colorado, Rio, gravel of 295 —— sand-dunes of 281, 294 —— Pampean formation near 355 Combarbala 479, 481 Concepcion, elevation of 305 —— deposits of 399, 405 —— crystalline rocks of 433 Conchalee, gravel-terraces of 311 Concretions of gypsum, at Iquique 345 —— in sandstone at S. Cruz 387 —— in tufaceous tuff of Chiloe 387 —— in gneiss 414 —— in claystone-porphyry at Port Desire 421 —— in gneiss at Valparaiso 435 —— in metamorphic rocks 436 —— of anhydrite 450 —— relations of, to veins 473 Conglomerate claystone of Chile 443, 445 —— of Tenuyan 454, 458, 478 —— of the Cumbre Pass 462, 466 —— of Rio Claro 485 —— of Copiapo 496, 499 Cook, Captain, on form of sea-bottom 300 Copiapo, elevation of 321 —— tertiary formations of 403 —— secondary formations of 489 Copper, sulphate of 489 —— native, at Arqueros 482 —— mines of, at Panuncillo 481 —— veins, distribution of 505 Coquimbo, elevation and terraces of 312 —— tertiary formations of 404 —— secondary formations of 482 Corallines living on pebbles 299 Cordillera, valleys bordered by gravel fringes 337 —— basal strata of 442 —— fossils of 453, 465, 486, 487, 493, 503 —— elevation of 442, 459, 474, 476, 500, 502, 510, 512, 517 —— gypseous formations of 450, 452, 461, 463, 479, 483, 489, 491, 503 —— claystone-porphyries of 442 —— andesitic rocks of 446 —— volcanoes of 447, 511, 517 Coste, M., on elevation of Lemus 303 Coy inlet, tertiary formation of 390 _Crassatella Lyellii_ 392 Cruickshanks, Mr., on elevation near Lima 327 Crystals of feldspar, gradual formation of, at Port Desire 422 Cumbre, Pass of, in Cordillera 502 Cuming, Mr., on habits of the Mesodesma 310 —— on range of living shells on west coast 407

Dana, Mr., on foliated rocks 438 —— on amygdaloids 444 Darwin, Mount 427 D’Aubuisson, on concretions 397 —— on foliated rocks 438 Decay, gradual, of upraised shells 323, 327 Decomposition of granite rocks 417 De la Beche, Sir H., his theoretical researches in geology 299 —— on the action of salt on calcareous rocks 327 —— on bent cleavage-laminæ 434 Denudation on coast of Patagonia 292, 300, 409 —— great powers of 410 —— of the Portillo range 456, 458 Deposits, saline 344 Despoblado, valley of 496, 497, 499 Detritus, nature of, in Cordillera 338 Devonshire, bent cleavage in 434 Dikes, in gneiss of Brazil 414, 418 —— near Rio de Janeiro 417 —— pseudo, at Port Desire 423 —— in Tierra del Fuego 426 —— in Chonos archipelago, containing quartz 432 —— near Concepcion, with quartz 434 —— granitic-porphyritic, at Valparaiso 435 —— rarely vesicular in Cordillera 347 —— absent in the central ridges of the Portillo pass 452 —— of the Portillo range, with grains of quartz 456 —— intersecting each other often 466 —— numerous at Copiapo 498 Domeyko, M., on the silver mines of Coquimbo 482 —— on the fossils of Coquimbo 486 D’Orbigny, M. A., on upraised shells of Monte Video 278 —— on elevated shells at St. Pedro 278 —— on elevated shells near B. Ayres 279 —— on elevation of S. Blas 281 —— on the sudden elevation of La Plata 293 —— on elevated shells near Cobija 322 —— on elevated shells near Arica 322 —— on the climate of Peru 324 —— on salt deposits of Cobija 345 —— on crystals of gypsum in salt-lakes 349 —— on absence of gypsum in the Pampean formation 353 —— on fossil remains from Bahia Blanca 359, 360 —— on fossil remains from the banks of the Parana 362 —— on the geology of St. Fé 363 —— on the age of Pampean formation 367, 376 —— on the _Mastodon Andium_ 379 —— on the geology of the Rio Negro 381 —— on the character of the Patagonian fossils 391 —— on fossils from Concepcion 399 —— —— from Coquimbo 404 —— —— from Payta 405 —— on fossil tertiary shells of Chile 406 —— on cretaceous fossils of Tierra del Fuego 426 —— —— from the Cordillera of Chile 453, 465, 486, 488, 493, 504

Earth, marine origin of 304, 308 Earthenware, fossil 326 Earthquake, effect of, at S. Maria 293 —— elevation during, at Lemus 303 —— of 1822, at Valparaiso 310 —— effects of, in shattering surface 325 —— fissures made by 325 —— probable effects on cleavage 325 Earthquakes in Pampas 290 Earthquake-waves, power of, in throwing up shells 310 —— effects of, near Lima 327 —— power of, in transporting boulders 344 Edmonston, Mr., on depths at which shells live at Valparaiso 309 Ehrenberg, Professor, on infusoria in the Pampean formation 355, 359, 362 —— on infusoria in the Patagonian formation 383, 384, 386, 391, 392 Elevation of La Plata 278 —— Brazil 279 —— Bahia Blanca 280, 357 —— San Blas 281 —— Patagonia 281, 291, 293 —— Tierra del Fuego 288 —— Falkland islands 290 —— Pampas 289, 377 —— Chonos archipelago 303 —— Chiloe 304 —— Chile 304 —— Valparaiso 307, 310 —— Coquimbo 312, 320 —— Guasco 320 —— Iquique 322 —— Cobija 322 —— Lima 323 —— sudden, at S. Maria 293 —— —— at Lemus 303 —— insensible, at Chiloe 304 —— —— at Valparaiso 311 —— —— at Coquimbo 314 —— axes of, at Chiloe 398, 405 —— —— at P. Rumena 398, 405 —— —— at Concepcion 398, 405 —— unfavourable for the accumulation of permanent deposits 410 —— lines of, parallel to cleavage and foliation 416, 417, 424, 428, 432, 434, 438 —— lines of, oblique to foliation 431 —— areas of, causing lines of elevation and cleavage 441 —— lines of, in the Cordillera 442 —— slow, in the Portillo range 475 —— two periods of, in Cordillera of Central Chile 476 —— of the Uspallata range 474 —— two periods of, in Cumbre Pass 476 —— horizontal, in the Cordillera of Copiapo 500 —— axes of, coincident with volcanic orifices 503 —— of the Cordillera, summary on 510, 513, 517 Elliott, Captain, on human remains 279 Ensenada, elevated shells of 278 Entre Rios, geology of 363 _Equus curvidens_ 364, 379 Epidote in Tierra del Fuego 426 —— in gneiss 435 —— frequent in Chile 445 —— in the Uspallata range 475 —— in porphyry of Coquimbo 482 Erman, M., on andesite 347 Escarpments, recent, of Patagonia 301 Extinction of fossil mammifers 370

Falkland islands, elevation of 290 —— pebbles on coast 297, 299 —— geology of 424 Falkner, on saline incrustations 347 Faults, great, in Cordillera 461, 469 Feldspar, earthy, metamorphosis of, at Port Desire 422 —— albitic 347 —— crystals of, with albite 347 —— orthitic, in conglomerate of Tenuyan 454 —— in granite of Portillo range 455 —— in porphyries in the Cumbre Pass 466 Feuillée on sea-level at Coquimbo 314 Fissures, relations of, to concretions 397 —— upfilled, at Port Desire 424 —— in clay-slate 470 Fitton, Dr., on the geology of Tierra del Fuego 427 Fitzroy, Captain, on the elevation of the Falkland islands 427 —— on the elevation of Concepcion 305 Foliation, definition of 414 —— of rocks at Bahia 414 —— Rio de Janeiro 415 —— Maldonado 418 —— Monte Video 420 —— S. Guitru-gueyu 421 —— Falkland I. 424 —— Tierra del Fuego 427 —— Chonos archipelago 430 —— Chiloe 433 —— Concepcion 434 —— Chile 435 —— discussion on 435 Forbes, Professor E., on cretaceous fossils of Concepcion 400 —— on cretaceous fossils and subsidence in Cumbre Pass 465 —— on fossils from Guasco 488 —— —— from Coquimbo 483, 487 —— —— from Copiapo 493 —— on depths at which shells live 409, 496 Formation, Pampean 352 —— —— area of 371 —— —— estuary origin 373 —— tertiary of Entre Rios 363 —— of Banda Oriental 365 —— volcanic, in Banda Oriental 367 —— of Patagonia 381 —— summary on 391 —— tertiary of Tierra del Fuego 391 —— —— of the Chonos archipelago 393 —— —— of Chiloe 394 —— —— of Chile 394 —— —— of Concepcion 398, 404 —— —— of Navidad 400 —— —— of Coquimbo 402 —— —— of Peru 404 —— —— subsidence during 402 —— volcanic, of Tres Montes 393 —— —— of Chiloe 394 —— —— old, near Maldonado 418 —— —— with laminar structure 440 —— —— ancient, in Tierra del Fuego 426 —— recent, absent on S. American coast 409 —— metamorphic, of claystone-porphyry of Patagonia 421, 440 —— foliation of 436 —— plutonic, with laminar structure 440 —— palaeozoic, of the Falkland I. 424 —— claystone, at Concepcion 433 —— Jurassic, of Cordillera 512 —— Neocomian, of the Portillo Pass 453 —— volcanic, of Cumbre Pass 465 —— gypseous, of Los Hornos 479, 487 —— —— of Coquimbo 482 —— —— of Guasco 487 —— —— of Copiapo 488 —— —— of Iquique 503 —— cretaceo-oolitic, of Coquimbo 486, 495 —— —— of Guasco 487, 494 —— —— of Copiapo 495 —— —— of Iquique 504 Fossils, Neocomian, of Portillo Pass 453 —— —— of Cumbre Pass 465 —— secondary, of Coquimbo 485 —— —— of Guasco 487 —— —— of Copiapo 494 —— —— of Iquique 503 —— palæozoic, from the Falklands 424 Fragments of hornblende-rock in gneiss 414 —— of gneiss in gneiss 416 Freyer, Lieutenant, on elevated shells of Arica 323 Frezier on sea-level at Coquimbo 314

Galapagos archipelago, pseudo-dikes of 424 Gallegos, Port, tertiary formation of 390 Garnets in gneiss 415 —— in mica-slate 427 —— at Panuncillo 481 Gardichaud, M., on granites of Brazil 417 Gay, M., on elevated shells 306 —— on boulders in the Cordillera 339, 341 —— on fossils from Cordillera of Coquimbo 487 Gill, Mr., on brickwork transported by an earthquake-wave 327 Gillies, Dr., on heights in the Cordillera 448 —— on extension of the Portillo range 458 Glen Roy, parallel roads of 319 —— sloping terraces of 340 Gneiss, near Bahia 414 —— of Rio de Janeiro 415 —— decomposition of 417 Gold, distribution of 506 Gorodona, formations near 362 Granite, axis of oblique, to foliation 431 —— andesitic 446 —— of Portillo range 455 —— veins of, quartzose 432, 475 —— pebble of, in porphyritic conglomerate 493 —— conglomerate 497 Grauwacke of Uspallata range 468 Gravel at bottom of sea 293, 298 —— formation of, in Patagonia 295 —— means of transportation of 298 —— strata of, inclined 467 Gravel-terraces in Cordillera 337 Greenough, Mr., on quartz veins 437 Greenstone, resulting from metamorphose hornblende-rock 419 —— of Tierra del Fuego 426 —— on the summit of the Campana of Quillota 442 —— porphyry 443 —— relation of, to clay-slate 443 _Gryphæa orientalis_ 483 Guasco, elevation of 321 —— secondary formation of 487 Guitru-gueyu, Sierra 421 Guyana, gneissic rocks of 415 Gypsum, nodules of, in gravel at Rio Negro 296 —— deposited from sea-water 327 —— deposits of, at Iquique 345 —— crystals of, in salt lakes 346 —— in Pampean formation 353 —— in tertiary formation of Patagonia 382, , , —— great formation of, in the Portillo Pass 461, 463 —— —— in the Cumbre Pass 461, 463 —— —— near Los Hornos 479 —— —— at Coquimbo 482 —— —— at Copiapo 490, 492 —— —— near Iquique 504 —— of San Lorenzo 504

Hall, Captain, on terraces at Coquimbo 316 Hamilton, Mr., on elevation near Tacna 323 Harlan, Dr., on human remains 279 Hayes, Mr. A., on nitrate of soda 346 Henslow, Professor, on concretions 437 Herbert, Captain, on valleys in the Himalaya 335 Herradura Bay, elevated shells of 315 —— tertiary formations of 402 Himalaya, valleys in 335 _Hippurites Chilensis_ 483, 486 Hitchcock, Professor, on dikes 414 Honestones, pseudo, of Coquimbo 483 —— of Copiapo 489 Hooker, Dr. J. D., on fossil beech-leaves 391 Hopkins, Mr., on axes of elevation oblique to foliation 432 —— on origin of lines of elevation 440, 512 Hornblende-rock, fragments of, in gneiss 414 Hornblende-schist, near M. Video 420 Hornos, Los, section near 479 Hornstone, dike of 433, 434 Horse, fossil tooth of 358, 364 Huafo island 393, 404 —— subsidence at 411 Huantajaya, mines of 503 Humboldt, on saline incrustations 347 —— on foliations of gneiss 415 —— on concretions in gneiss 435

Icebergs, action on cleavage 434, 436 Illapele, section near 479 Imperial, beds of shells near 305 Incrustations, saline 347 Infusoria in Pampean formation 352, 355, 360, 363 —— in Patagonian formation 382, 383, 384, 391 Iodine, salts of 347, 348 Iquique, elevation of 322 —— saliferous deposits of 344 —— cretaceo-oolitic formation of 503 Iron, oxide of, in lavas 463, 499 —— in sedimentary beds 480, 482 —— tendency in, to produce hollow concretions 398 —— sulphate of 489 Isabelle, M., on volcanic rocks of Banda Oriental 368

Joints in clay-slate 428 Jukes, Mr., on cleavage in Newfoundland 437

Kamtschatka, andesite of 347 Kane, Dr., on the production of carbonate of soda 328 King George’s sound, calcareous beds of 312

Lakes, origin of 300 —— fresh-water, near salt lakes 350 Lava, basaltic, of S. Cruz 389 —— claystone-porphyry, at Chiloe 395 —— —— ancient submarine 446 —— basaltic, of the Portillo range 457 —— feldspathic, of the Cumbre Pass 463 —— submarine, of the Uspallata range 471, 473, 476 —— basaltic, of the Uspallata range 475 —— submarine, of Coquimbo 484, 486 —— of Copiapo 490, 496, 499 Lemus island 393, 404 Lemuy islet 394 Lignite of Chiloe 395 —— of Concepcion 398 Lima, elevation of 323 Lime, muriate of 328, 344, 347 Limestone of Cumbre Pass 462 —— of Coquimbo 483, 485 —— of Copiapo 493 Lund and Clausen on remains of caves in Brazil 378, 380 Lund, M., on granites of Brazil 417 Lyell, M., on upraised shells retaining their colours 289 —— on terraces at Coquimbo 315 —— on elevation near Lima 327 —— on fossil horse’s tooth 364 —— on the boulder-formation being anterior to the extinction of North American mammifers 371 —— on quadrupeds washed down by floods 374 —— on age of American fossil mammifers 379 —— on changes of climate 409 —— on denudation 410 —— on foliation 438

MacCulloch, Dr., on concretions 437 —— on beds of marble 440 Maclaren, Mr., letter to, on coral-formations 413 _Macrauchenia Patachonica_ 358, 370 Madeira, subsidence of 302 Magellan, Strait, elevation near, of 288 Magnesia, sulphate of, in veins 387 Malcolmson, Dr., on trees carried out to sea 475 Maldonado, elevation of 277 —— Pampean formation of 365 —— crystalline rocks of 418 Mammalia, fossil, of Bahia Blanca 356, 364 —— —— near St. Fé 363 —— —— of Banda Oriental 366 —— —— of St. Julian 369 —— —— at Port Gallegos 391 —— washed down by floods 373 —— number of remains of, and range of, in Pampas 376 Man, skeletons of (Brazil) 279 —— remains of, near Lima 325 —— Indian, antiquity of 325 Marble, beds of 418 Maricongo, ravine of 500 Marsden, on elevation of Sumatra 305 _Mastodon Andium_, remains of 362 —— range of 378 Maypu, Rio, mouth of, with upraised shells 307 —— gravel fringes of 339 —— debouchement from the Cordillera 449 Megalonyx, range of 379 Megatherium, range of 379 Miers, Mr., on elevated shells 311 —— on the height of the Uspallata plain 335 Minas, Las 418 Mocha Island, elevation of 305 —— tertiary form of 398 —— subsidence at 411 Molina, on a great flood 341 Monte Hermoso, elevation of 280 —— fossils of 355 Monte Video, elevation of 278 —— Pampean formation of 365 —— crystalline rocks of 419 Morris and Sharpe, Messrs., on the palæozoic fossils of the Falklands 424 Mud, Pampean 352 —— long deposited on the same area 376 Murchison, Sir R., on cleavage 436 —— on waves transporting gravel 299 —— on origin of salt formations 505 —— on the relations of metalliferous veins and intrusive rocks 507 —— on the absence of granite in the Ural 512

_Nautilus d’Orbignyanus_ 400, 405 Navidad, tertiary formations of, subsidence of 400, 411 Negro, Rio, pumice of pebbles of 281 —— gravel of 295 —— salt lakes of 295 —— tertiary strata of 384 North America, fossil remains of 379 North Wales, sloping terraces absent in 340 —— bent cleavage of 434 Neuvo Gulf, plains of 282 —— tertiary formation of 384

Owen, Professor, on fossil mammiferous remains 356, 358, 364, 366, 370

Palmer, Mr., on transportation of gravel 300 Pampas, elevation of 290 —— earthquakes of 290 —— formation of 295, 350 —— localities in which fossil mammifers have been found 380 Panuncillo, mines of 481 Parana, Rio, on saline incrustations 347 —— Pampean formations near 361 —— on the S. Tandil 420 Parish, Sir W., on elevated shells near Buenos Ayres 278, 279 —— on earthquakes in the Pampas 290 —— on fresh-water near salt lakes 350 —— on origin of Pampean formation 373 Patagonia, elevation and plains of 281 —— denudation of 291 —— gravel-formation of 295 —— sea-cliffs of 301 —— subsidence during tertiary period 411 —— crystalline rocks of 421 Payta, tertiary formations of 404 Pebbles of pumice 280 —— decrease in size on the coast of Patagonia 293 —— means of transportation 298 —— encrusted with living corallines 299 —— distribution of, at the eastern foot of Cordillera 337 —— dispersal of, in the Pampas 354 —— zoned with colour 443 Pentland, Mr., on heights in the Cordillera 460 —— on fossils of the Cordillera 465 Pernambuco 279 Peru, tertiary formations of 403 Peuquenes, Pass of, in the Cordillera 448 —— ridge of 452 Pholas, elevated shells of 303 Pitchstone of Chiloe 395 —— of Port Desire 421 —— near Cauquenes 448 —— layers of, in the Uspallata range 472 —— of Los Hornos 480 —— of Coquimbo 483 Plains of Patagonia 282, 291 —— of Chiloe 304 —— of Chile 333 —— of Uspallata 335 —— on eastern foot of Cordillera 336 —— of Iquique 346 Plata, La, elevation of 277 —— tertiary formation of 295, 353 —— crystalline rocks of 418 Playfair, Professor, on the transportation of gravel 300 Pluclaro, axis of 483 Pondicherry, fossils of 400 Porcelain rocks of Port Desire 422 —— of the Uspallata range 471, 473, 476 Porphyry, pebbles of, strewed over Patagonia 296 Porphyry, claystone, of Chiloe 395 —— —— of Patagonia 421 —— —— of Chile 442, 445 —— greenstone, of Chile 444 —— doubly columnar 448 —— claystone, rare, on the eastern side of the Portillo Pass 454 —— brick-red and orthitic, of Cumbre Pass 458, 467 —— intrusive, repeatedly injected 467 —— claystone of the Uspallata range 468 —— —— of Copiapo 489, 499 —— —— eruptive sources of 502 Port Desire, elevation and plains of 283 —— tertiary formation of 383 —— porphyries of 421 Portillo Pass in the Cordillera 448 Portillo chain 454, 458 —— compared with that of the Uspallata 478 Prefil or sea-wall of Valparaiso 310 Puente del Inca, section of 461 Pumice, pebbles of 230 —— conglomerate of R. Negro 382 —— hills of, in the Cordillera 347 Punta Alta, elevation of 280 —— beds of 356

Quartz-rock of the S. Ventana 421 —— C. Blanco 421 —— Falkland islands 424 —— Portillo range 455 —— viscidity of 475 —— veins of, near Monte Video 420 —— —— in dike of greenstone 426 —— grains of, in mica slate 430 —— —— in dikes 432, 434 —— veins of, relations to cleavage 437 Quillota, Campana of 442 Quintero, elevation of 311 Quiriquina, elevation of 306 —— deposits of 399

Rancagua, plain of 334 Rapel, R., elevation near 307 Reeks, Mr. T., his analysis of decomposed shells 328 —— his analysis of salts 344 Remains, human 324 Rio de Janeiro, elevation near 279 —— crystalline rocks of 415 Rivers, small power of transporting pebbles 298 —— small power of, in forming valleys 343 —— drainage of, in the Cordillera 449, 513 Roads, parallel, of Glen Roy 319 Rocks, volcanic, of Banda Oriental 367 —— Tres Montes 393 —— Chiloe 394 —— Tierra del Fuego 426 —— with laminar structure 440 Rodents, fossil, remains of 356 Rogers, Professor, address to Association of American Geologists 412 Rose, Professor G., on sulphate of iron at Copiapo 489

S. Blas, elevation of 281 S. Cruz, elevation and plains of 284 —— valley of 285 —— nature of gravel in valley of 296 —— boulder formation of 371 —— tertiary formation of 386 —— subsidence at 412 S. Fé Bajada, formations of 363 S. George’s bay, plains of 282 S. Helena island, sea-cliffs, and subsidence of 301 S. Josef, elevation of 281 —— tertiary formation of 383 S. Juan, elevation near 278 S. Julian, elevation and plains of 284 —— salt lake of 348 —— earthy deposit with mammiferous remains 369 —— tertiary formations of 384 —— subsidence at 411 S. Lorenzo, elevation of 323 —— old salt formation of 504 S. Mary, island of, elevation of 305 S. Pedro, elevation of 278 Salado, R., elevated shells of 279 —— Pampean formation of 353 Salines 348 Salt, with upraised shell 324, 327 —— lakes of 348 —— purity of, in salt lakes 349 —— deliquescent, necessary for the preservation of meat 349 —— ancient formation of, at Iquique 504 —— —— at S. Lorenzo 504 —— strata of, origin of 505 Salts, superficial deposits of 344 Sand-dunes of the Uruguay 279 —— of the Pampas 281 —— near Bahia Blanca 281, 293 —— of the Colorado 281, 294 —— of S. Cruz 286 —— of Arica 323 Sarmiento, Mount 427 Schmidtmeyer on auriferous detritus 506 Schomburghk, Sir R., on sea-bottom 299 —— on the rocks of Guyana 415 Scotland, sloping terraces of 340 Sea, nature of bottom of, off Patagonia 292 —— power of, in forming valleys 343 Sea cliffs, formation of 301 Seale, Mr., model of St. Helena 301 Sebastian Bay, tertiary formation of 391 Sedgwick, Professor, on cleavage 336 Serpentine of Copiapo 489 Serpulæ, on upraised rocks 325 Shale-rock, of the Portillo Pass 452 —— of Copiapo 493 Shells, upraised state of, in Patagonia 288 —— elevated, too small for human food 308 —— transported far inland, for food 309 —— upraised, proportional numbers varying 312, 324 —— —— gradual decay of 323, 324, 327 —— —— absent on high plains of Chile 335 —— —— near Bahia Blanca 358 —— preserved in concretions 394, 397 —— living and fossil range of, on west coast 406, 408 —— living, different on the east and west coast 411 Shingle of Patagonia 295 Siau, M., on sea-bottom 299 Silver mines of Arqueros 431 —— of Chanuncillo 494 —— of Iquique 503 —— distribution of 506 Slip, great, at S. Cruz 387 Smith, Mr., of Jordan Hill, on upraised shells retaining their colours 289 —— on Madeira 302 —— on elevated seaweed 325 —— on inclined gravel beds 467 Soda, nitrate of 346 —— sulphate of, near Bahia Blanca 348, 349 —— carbonate of 347 Soundings off Patagonia 293, 299 —— in Tierra del Fuego 300 Spirifers 486, 488 Spix and Martius on Brazil 417 Sprengel on the production of carbonate of soda 328 Springs, mineral, in the Cumbre Pass 461 Stratification of sandstone in metamorphic rocks 414 —— of clay-slate in Tierra del Fuego 428 —— of the Cordillera of Central Chile 442, 448, 461 —— little disturbed in Cumbre Pass 460, 466 —— disturbance of, near Copiapo 501 Streams of lava at S. Cruz, inclination of 390 —— in the Portillo range 457 String of cotton with fossil-shells 325 _Struthiolaria ornata_ 392 Studer, M., on metamorphic rocks 438 Subsidence during formation of sea-cliffs 301 —— near Lima 327 —— probable, during Pampean formation 376 —— necessary for the accumulation of permanent deposits 411 —— during the tertiary formations of Chile and Patagonia 413 —— probable during the Neocomian formation of the Portillo Pass 453 —— probable during the formation of conglomerate of Tenuyan 459 —— during the Neocomian formation of the Cumbre Pass 465 —— of the Uspallata range 474, 477 —— great, at Copiapo 496 —— —— during the formation of the Cordillera 510 Sulphur, volcanic exhalations of 509 Sumatra, promontories of 305 Summary on the recent elevatory movements 259, 329, 514 —— on the Pampean formation 371, 515 —— on the tertiary formations of Patagonia and Chile 391, 404, 513 —— on the Chilean Cordillera 508 —— on the cretaceo-oolitic formation 508 —— on the subsidences of the Cordillera 509 —— on the elevation of the Cordillera 511, 517

Tacna, elevation of 323 Tampico, elevated shells near 329 Tandil, crystalline rocks of 420 Tapalguen, Pampean formation of 353 —— crystalline rocks of 420 Taylor, Mr., on copper veins of Cuba 506 Temperature of Chile during the tertiary period 408 Tension, lines of, origin of, axes of elevation and of cleavage 440 Tenuy Point, singular section of 395 Tenuyan, valley of 454, 478 Terraces of the valley of S. Cruz 286 —— of equable heights throughout Patagonia 290 —— of Patagonia, formation of 294 —— of Chiloe 304 —— at Conchalee 311 —— of Coquimbo 316 —— not horizontal at Coquimbo 317 —— of Guasco 320 —— of S. Lorenzo 323 —— of gravel within the Cordillera 337 Theories on the origin of the Pampean formation 372 Tierra Amarilla 489 Tierra del Fuego, form of sea-bottom 300 —— tertiary formations of 391 —— clay-slate formation of 424 —— cretaceous formation of 426 —— crystalline rocks of 426 —— cleavage of clay-slate 427, 436 Tosca rock 352 Trachyte of Chiloe 394 —— of Port Desire 421 —— in the Cordillera 347 Traditions of promontories having been islands 305 —— on changes of level near Lima 327 Trees buried in plain of Iquique 346 —— silicified, vertical, of the Uspallata range 473 Tres Montes, elevation of 303 —— volcanic rocks of 393 _Trigonocelia insolita_ 392 Tristan Arroyo, elevated shells of 278 Tschudi, Mr., on subsidence near Lima 327 Tuff, calcareous, at Coquimbo 313 —— on basin-plain near St. Jago 334 —— structure of, in Pampas 352 —— origin of, in Pampas 374 —— pumiceous, of R. Negro 382 —— Nuevo Gulf 383 —— Port Desire 383 —— S. Cruz 386 —— Patagonia, summary on Chiloe 391 —— formation of, in Portillo chain 395 —— great deposit of, at Copiapo 457 Tuffs, volcanic, metamorphic, of Uspallata 471 —— of Coquimbo 484

Ulloa, on rain in Peru 324 —— on elevation near Lima 327 Uruguay, Rio, elevation of country near 278 Uspallata, plain of 335, 515 —— pass of 459 —— range of 368 —— concluding remarks on 476

Valdivia, tertiary beds of 398 —— mica-slate of 433 Valley of S. Cruz, structure of 285 —— Coquimbo 314 —— Guasco, structure of 320 —— Copiapo, structure of 321 —— S. Cruz, tertiary formations of 386 —— Coquimbo, geology of 482 —— Guasco, secondary formations of 487 —— Copiapo, secondary formations of 488 —— Despoblado 496, 497, 499 Valleys in the Cordillera bordered by gravel fringes 337 —— formation of 338 —— in the Cordillera 449 Valparaiso, elevation of 307 —— gneiss of 435 Vein of quartz near Monte Video 419 —— in mica-slate 430 —— relations of, to cleavage 437 —— in a trap dike 426 —— of granite, quartzose 432, 475 —— remarkable, in gneiss, near Valparaiso 435 Veins, relations of, to concretions 396 —— metalliferous, of the Uspallata range 475 —— metalliferous, discussion on 505 Venezuela, gneissic rocks of 415 Ventana, Sierra, Pampean formation near 353 —— quartz-rock of 421 Villa Vincencio Pass 468 Volcan, Rio, mouth of 449 —— fossils of 453 Volcanoes of the Cordillera 392, 447, 511 —— absent, except near bodies of water 457 —— ancient submarine, in Cordillera 502 —— action of, in relation to changes of level 514 —— long action of, in the Cordillera 517

Wafer on elevated shells 322 Waves caused by earthquakes, power of, in transporting boulders 326, 344 —— power of, in throwing up shells 309 Weaver, Mr., on elevated shells 329 White, Martin, on sea-bottom 299 Wood, silicified, of Entre Rios 364 —— S. Cruz 388 —— Chiloe 394, 396 —— Uspallata range 473 —— Los Hornos 479 —— Copiapo 495, 497

Yeso, Rio, and plain of 450 Ypun Island, tertiary formation of 393

Zeagonite 426