Analysis of the Water of the Rio Vinagre, in the Andes of Popayan, by M. Mariano de Rivero; with geognostic and physical Illustrations of some Phaenomena which are exhibited by Sulphur, Sulphuretted Hydrogen, and Water, in Volcanos.

By M. A. de Humboldt.

[Extract of a Letter dated the 8th October 1823.]

"IN compliance with the desire of M. de Humboldt, I procured some of the water of Rio Vinagre.

It was sent to me by M. Torres, who takes an interest in all that can contribute to scientific researches.

This water has yielded per litre: sulphuric acid, 1·080; muriatic acid, 0·184; alumine, 0.240; lime, 0.160; and some indications of iron.

The presence of muriatic acid confirms the observations made on the vapours and the stony productions of Vesuvius and of several other volcanos."

It cannot be doubted that the indications are by grammes and fractions of grammes: a litre of the water of the Rio Vinagre includes 1·080 gramme of sulphuric acid and 0·184 gramme of muriatic acid.

This proportion of sulphuric acid, is nevertheless very sensible to the taste, and is manifested by an abundant precipitate with the salts of barytes. [The litre being 2·113 pints, the contents of the water in English grains will be as follows: sulphuric acid 16·68; muriatic acid 2·84; alumine 3·7; lime 2·47.-Edit.]

Rivero.

I had made known, at the time of my return from America, the presence of the sulphuric and muriatic acids in the water of the Rio Vinagre, which the aborigines call Pusambio (See Views of the Cordilleras, and Monuments of the People of America, vol. ii. p. 166; Barometric Levelling of the Andes, No. 126; Caldas, Semanario del Nuevo Reyno de Granada, t. i. p. 265); but not being furnished with the salts of barytes, I had engaged MM. Rivero and Boussingault, when they departed for Bogota, to verify these facts.

The analysis, which we owe to one of these expert chemists, is the first which has been attempted on the water of the Rio Vinagre. I shall give some extracts from the journal of my travels, in great part still unpublished, explanatory of the local circumstances.

The town of Popayan is situated in the beautiful valley of the Rio Cauca, on the Bogota road to Quito, at the foot of the two great volcanos of Purace and Sotara.

These volcanos, almost extinct, and exhibiting only the phaenomena of solfataras, form part of the central chain of the Andes of New Granada. At 1° 55' and 2° 20' of north latitude, the group of mountains which incloses the sources of the Magdalena is divided into three branches, of which the eastern is continued towards Timana and the Nevados of Chita and of Merida; the intermediate and central one towards the Paramos of Guanacas and of Quimdiu; the western towards the platiniferous district of the Choco and the isthmus of Panama.

In ascending from the town of Popayan to the summit of the volcano of Purace, M.

Bompland and I found at the height of 8672 feet a little plain (Llano del Corazon), inhabited by poor Indian husbandmen.

This plain is separated from the rest of the acclivity, with which it would otherwise be continuous, by two ravines extremely deep: it is at the edge of these precipices that the village of Purace is built.

Springs rise every where from the trachytic rock; each garden is surrounded with a quickset hedge of narrow-leaved euphorbium (lechero) of the most delicate green.

This beautiful verdure contrasts in a striking manner with the back-ground of black and arid mountains which surround the volcano, and which are rent by the effects of the earthquakes.

The site of the village is celebrated in the country on account of three beautiful cascades (choreras) of the river of Pusambio, whose water is acid, and which the people, who know no other acid than vinegar, call Rio Vinagre, sometimes Gran Vinagre.

This river takes its rise at the height of nearly 10,871 feet, in a very inaccessible spot.

Although the temperature of the water be little different in the lower cascades from that of the surrounding atmosphere, it is not less certain that the sources of the Rio Pusambio or Vinagre are very hot.

This fact was attested to me by the natives and by the missionary of the village of Purace.

In going to the summit of the volcano I saw a column of smoke rise at the place where the acid waters make their appearance.

I have drawn the second of the falls of the Vinagre (plate xxx.

of the Views of the Cordilleras): the water, which opens itself a passage across a cavern, is precipitated more than 383 feet in depth.

The fall has a very picturesque effect; but the inhabitants of Popayan would be better pleased if the river, instead of throwing itself into the Rio Cauca, became engulfed in some other crevice; for such is the delicacy of constitution of animals which breathe by gills, and which absorb the oxygen dissolved in the water, that the Cauca during a course of four leagues is destitute of fish, on account of the mixture of its waters with those of the Rio Vinagre, which are charged both with oxide of iron and with sulphuric and muriatic acid.

After staying a considerable time on the craggy wall of rock which borders the cascade, a pricking sensation is felt in the eyes from the minute spray in the atmosphere.

Fish re-appear in the Rio Cauca at the point where it becomes enlarged by the influx of the Pindamon and of the Palace.

M. Caldas has even attributed to this mixture, doubtless with little reason, the absence of goitres in the valley of Rio Cauca.

-- Semanario, t. i. p. 265. See my Memoir on the Goitres in the Cordilleras.

-- (Magendic, Jour. de Physiol. t. iv. p. 109.)

Journal de Physique, t. lxii. p. 61.

A little to the north of the sources of the Pusambio rise two other rivulets charged in like manner with free sulphuric acid, which the people call the Little Vinegars (los dos Vinagres chicos): they throw themselves into the Rio de San Francisco, which is itself but a tributary of the Gran Vinagre.

During my stay at Popayan, it was an opinion generally received that all these acid waters contained some iron dissolved by a great quantity of carbonic acid.

When it was merely remembered that the sources of the Vinagre are very hot, this opinion ought to have been abandoned.

I boiled some water taken from the cascade; and I found, after the ebullition, the same acid taste and the same precipitates as in the unboiled water.

At this period I had very few re-agents left.

The nitrate of silver gave a white and milky precipitate, indicating the presence of muriates.

The presence of iron was shown by the prussiate of lime, that of lime by the oxalate of potash.

When the water was weighed with great care in the office of the mint of Popayan, the weight of an equal quantity of the water of the Vinagre was found to be to that of distilled water as 2735 [Formel] gr. to 2731 gr.; that is to say, that the specific gravity of the water of the cascade was 1,0015.

The conjoint presence of the sulphuric and muriatic acids has also been observed by M. Vauquelin in the water which M. Leschenault had taken from the crater-lake of Mount Idienne in Java (Journal de Physique, t. lxv. p. 406.)

See Phil. Mag. vol. xlii. pp. 126, 182.

The waters which I describe, and of which M. Rivero has given the first analysis, must not be confounded with those of the two subterraneous lakes which we have found near the summit of the volcano; one is 14,356 feet high, the other, above the snows, 15,475 feet.

This volcano of Purace is a dome of semivitreous trachyte, of a blueish grey and having a conchoidal fracture.

It does not present a great crater at its summit, but several little mouths.

It differs very much from the neighbouring volcano, the Sotara, which is of a conical form, and which has thrown out an immense quantity of obsidians.

These masses, covering the plains of Julumito, are balls or tears of obsidian, the surface of which is often tubercular.

They present, what I have seen nowhere else in the two hemispheres, all the shades of colour, from deep black to that of an artificial glass entirely colourless.

It may appear surprising to see that this deprivation of colour has not been accompanied by any inflation or porosity.

The obsidians of Sotara are mixed with fragments of enamel which resemble the porcelain of Reaumur, and adhering to which I have found masses of felspar which have resisted fusion.

Here, as in the Andes of Quito, as at Mexico and at the Canary Islands, the system of basaltic rocks lies far from the trachytes which form the volcanos of Purace and of Soltara.

The basalts of the Tetilla of Julumito belong only to the left bank of the Cauca.

They rise from transition porphyries free from augite, containing some hornblende, a very little quartz in small crystals embedded in the mass, and a felspar which passes from the common to the vitreous variety.

This porphyry is covered, near to Los Serillos, with a blackish-gray lime-stone traversed by veins of carbonate of lime, and so much overcharged with carbon that in some parts it stains the fingers like an aluminous schist, or like the lydian stone of Steeben in the Fichtelgebirge.

The trachytic dome of Purace which gives birth to the little river of sulphuric acid, rises out of a porphyritic syenite (with common felspar), which in its turn is superposed on transition granite abounding in mica.

This observation , very important for the position of volcanic rocks, may be made near to Santa Barbara in ascending from Popayan to the village of Purace.

The volcano, like the most part of the great volcanos of the Andes, presents layers or mantles of melted stony matter, not real currents of lava.

Some fragments of granular limestone, probably magnesian, which I found at more than 12,790 feet high, seem to have been thrown up through crevices which have since become closed.

They are like those of the Fosso Grande of Vesuvius, which owe their granular texture to volcanic fire.

It is not possible to go on horseback further than the cascades of the Rio Vinagre.

From thence we were eight hours in mounting on foot to the summit of the volcano and in descending from it.

The weather was dreadful; snow and hail fell.

I had a great deal of difficulty in lighting the tinder at the point of the conductor of Volta's electrometer; the balls of elder-pith separated from 5 to 6 lines, and the electricity passed often from positive to negative without there being any other symptom of storm: for thunder and lightning are (according to my experience) generally very rare when we are above 12,800 or 14,000 feet high.

The hail was white; the hailstones, from five to seven lines in diameter, composed of layers varying in translucency.

They were not only much flattened towards the poles, but so much increased in their equatorial diameter, that rings of ice separated themselves on the least shock.

I had already twice observed and described this phaenomenon, in the mountains of Bareuth, and near Cracow, during a journey in Poland. Can it be admitted that the successive layers which are added to the central nucleus are in a state of fluidity so great that the rotary motion can cause the flattening of the spheroids?

M. Vauquelin has recently proved by a direct analysis the presence of carbon in the purest lydian stones.

I had found, in a series of experiments made on the galvanic exciters in 1798, that the lydian stones of the transition schists of Steeben produced jointly with zinc the same effect as graphite or carburet of iron.

I have since made some trials to prove chemically the presence of carbon in several varieties of lydian stone.--See my Experiments on the Nervous and Muscular Fibre (in German), t. ii. pp. 163.

See an account of the whole of these phaenomena of the volcanos of Popayan in my Essai sur le Gisement des Roches, 1823, pp. 129, 139, 340.

I have already remarked elsewhere in the Ann.

de Chimie, that at Paramo de Guanacas, where the road from Bogota to Popayan passes to the height of 14,700 feet, there has been seen fall, not snow, but red hail.

Did it inclose those same germs of vegetable organization which have been discovered above the polar circle?

When the barometer indicated that we were come very near the limit of perpetual snow, we found the masses of sulphur disseminated in imperfectly columnar trachytic rocks augmented.

This phaenomenon struck me the more, as I knew how rare sulphur is on the sides of inflamed volcanos:--a column of yellowish smoke and a frightful noise informed us of the neighbourhood of one of the mouths (bocas) of the volcano.

We had some trouble to approach its edge; the declivity of the mountain being very steep, and the crevices only covered by a crust of sulphur, of whose thickness we were ignorant.

We believed we might rate the extent of this crust, which is often interrupted by rocks, at more than 12,000 square feet.

These little ridges of trachytic rocks act strongly on the magnet.

I tried to keep at as much distance from them as possible, to determine the inclination of the needle.

It was at the town of Popayan (height 5825 English feet) 23°,05, centesimal division; at the village of Purace (height 8671 feet) 21°,81; near the summit of the volcano of Purace (height 14,542 feet) 20°,85.

The intensity of the magnetic force varied very little at Popayan and at the village of Purace; and the diminution of the inclination is certainly not the effect of the height, as is proved by so many other observations which I have made on the summit of the Andes, but the effect of local attractions depending on certain centres of action in the trachytes.

The mouth of the volcano of Purace is a perpendicular cleft, the visible opening of which is only 6 feet long and 3 broad. It is covered in form of a vault by a layer of very pure sulphur, which is 18 inches thick, and which the force of the elastic vapours has split on the north side.

At the distance of 12 feet from the mouth we felt an agreeable heat.

The centigrade thermometer, which had kept till then at 6°,2 (43° F.) (a cold not at all considerable in a time of hail, and at a height of 14,356 feet), rose to 15° (61° F.).

Placed in such a manner as not to be incommoded by the vapours, we had the pleasure of drying our clothes.

The frightful noise which is heard near this opening has almost always the same intensity: it can only be compared to that which would be caused by several steam-engines together, were the dense steam suffered to escape from all at the same moment.

We threw great stones into the crevice, and we discovered on this occasion that the opening communicated with a basin full of boiling water.

The vapours which escape with so much violence are of the sulphurous acid, which is indicated by their suffocating smell.

We shall soon see that the water of the subterraneous lake is charged with sulphuretted hydrogen; but the odour of this gas is not smelt at the summit of the volcano, because it is disguised by the much stronger smell of the sulphurous acid vapours.

I had not any means of determining the temperature of these vapours, which seem to undergo a prodigiously strong pressure in the interior of the volcano.

As the Indians pretend that the opening has several compartments which are not all filled with water, and that the noise which is heard at times in the interior of the crevice is the forerunner of flames, I introduced, by means of a long pole, some papers coloured with the tincture of violet, under the vault, where I could be sure of not touching the surface of the water.

Drawing back the pole, I found the papers strongly reddened, but not at all inflamed, as was easy to be foreseen.

We suceeded after several vain attempts in obtaining some water from the crevice: this was by tying a tutuma (the fruit of the Crescentia Cujete) to a stick 8 feet long. The water was directly poured into a bottle hermetically stopped.

We examined it on our return to the village of Purace: it exhaled a strong smell of sulphuretted hydrogen; it had no acid taste, but some weak precipitates caused by the nitrate of silver showed the presence of muriatic acid.

The crust of sulphur which forms above the mouth arises without doubt from the contact of the vapours of sulphurous acid with the sulphuretted hydrogen which the subterraneous lake disengages.

Even the water of this lake is covered with a coat of sulphur, which disappeared in the places where we threw the stones.

It results from these observations, that only the presence of the muriatic acid, or of combinations of this acid with salifiable bases, indicates a feeble analogy between the waters of Rio Vinagre and those of the lakes.

The first, which spring much lower, at the declivity of the volcano of Purace, are charged with free sulphuric acid: the others, which are found at the summit of the volcano, contain sulphuretted hydrogen.

As the upper mouths are found at very different heights above the level of the sea, it may be supposed that their subterraneous waters are owing to the melting of the snows, and that they do not communicate.

The Rio Vinagre receives its acid in the interior of a volcano which abounds in sulphur, and the temperature of which appears extremely elevated, although for centuries no luminous phaenomenon has been perceived at its summit.

The good curate of the village of Purace thought to render a great service to his parishioners, as well as to the inhabitants of the town of Popayan, in causing, as he said, the chimneys of the volcano to be cleaned now and then. He ordered the Indians to take away the crust of sulphur which rises in form of a dome above the crevice.

This crust has acquired sometimes, as they affirm, a thickness of as much as four feet in less than two years.

It lessens without doubt the opening by which the vapours of sulphurous acid escape; but it may be conceived that the elastic force of these vapours is such that, if the opening were entirely stopped up for some moments, it would sooner break the new arch than produce commotions by acting against the rocky sides of the volcano.

For several years the lakes, which represent in miniature the crater-lakes of our extinguished volcanos, seem each to preserve the same level of their line of water; which proves that the evaporation is equal to the infiltration of the waters of snow and rain: but this equilibrium has not always been equally steady.

About the year 1790 the Boca grande caused partial inundations.

I dwell on this phaenomenon, because it seems to throw some light on a problem of the geology of volcanos, which has not been sufficiently examined: I mean the ejections of water and mud.

At Vesuvius these ejections are only apparent, and come neither from the interior of the crater nor from the lateral crevices.

An immense electric tension manifests itself in the atmosphere which surrounds the summit of the volcano at the time of great eruptions.

Flashes of lightning cleave the air; the aqueous vapours thrown out by the crater are cooled; thick clouds envelop the summit during the continuance of this storm, confined to a little space; the water descends in torrents, and is mixed with the tufaceous substances which it drags with it . These effects, purely meteorological, have given rise to the traditions about boiling waters that issued from the crater of Vesuvius in 1631; fabulous traditions, which are perpetuated by an inscription at Portici.

M. de la Condamine (Memoires de l'Academie 1754, p. 18) had already expressed very precise ideas on the cause of these phaenomena, which are found equally well explained in the Storia dell' incendio del 1737, published by the Academy of Naples. I saw in my last journey to Naples, (December 1822,) the ravages caused by the torrents of water from the side of Ottajano, at the foot of Vesuvius.

They had transported into the plain, not only mud, but masses of lava 48 feet in circumference and 25 feet high.

See the excellent description of these phaenomena by MM. Monticelli and Covelli.

(Storia del Vesuvio degli anni 1821--1823, p. 91--98.)

Phil. Mag. vol. lxiii. p. 46.

By the mixture of the rain and the volcanic cinders, there is formed in the air (l. c. p. 94) a kind of pisolites with concentric layers, which I also found on the plain of Hambato, among the ancient ejections of the Carguairazo.

The inhabitants of the province of Quito call these pisolites earth hailstones.

In the volcanos of the Andes which exceed the limit of perpetual snow, the causes of inundations are very different from those which we have just indicated.

As the eruptions of these colossal summits take place only after long intervals (every thirty or forty years, or still more rarely), banks of snow of an enormous thickness accumulate on the sides of the mountains.

These snows do not melt at the time of the explosion only, but sometimes several days before.

Thus in February 1803, during my stay at Guayaquil, the inhabitants of the province of Quito were frightened at the appearance of the cone of Cotopaxi, which lost a great part of its snows in a single night, and showed plainly the black colour of its burnt rocks.

Whatever idea may be formed of the power of the volcanic forces, and of the intensity of the subterraneous fires in the Andes, it cannot be admitted that the thick sides of a cone could be uniformly warmed, and transmit the heat with such rapidity (by the conductibility of their mass) to the outside.

The sudden melting of the snows, when, in the Cordilleras, it precedes the eruptions, is probably owing only to an infinity of little fumaroles which disengage hot vapours through the fissured rock of the cone.

These vapours, according to what I have had opportunity of observing in the craters of Vesuvius, the Peak of Teneriffe, and the volcano of Jorullo in Mexico, are most frequently pure water, which does not act at all on the most sensible re-agents; at other times they contain muriatic acid.

It is remarked that the same crevice gives, at very near epochs, distilled (pure) water and very acid waters.

The artificial spring which M. Gimbernat has had the ingenious idea of forming at the summit of Vesuvius, by the condensation of the vapours in a glass tube, has sometimes shown these variations: they prove either the change of chemical action in the interior of the volcano, or the accidental opening of some new communications.

In the Andes of Quito, as in Iceland, and in the eruptions of AEtna of March 23, 1536, and March 6, 1755, the sudden melting of the banks of snow produced great devastations.

Ferrara, Campi Flegrei, 1810, p. 165.--Idem, Descriz, dell' Etna, 1818, p. 89, 116--120.

At other times, by slow infiltrations the snow waters are accumulated in the lateral cavities of the volcano; shocks of violent earthquakes, which do not always coincide with the epoch of the fiery eruptions, open these cavities; and waters long kept in, which support little fish of the genus Pimelodes, carry with them pulverized trachytes, pumice-stones, tufas, and other incoherent matters.

These liquid ejections spread sterility over the plains for centuries.

Muddy clays (lodazales) covered a space of more than four square leagues, when, in the night of the 19th of June 1698, the Peak of Carguairazo, the actual height of which exceeds 15,700 feet, sunk down with a noise.

The lakes of sulphureous water that we found at the summit of Purace, explain what the inhabitants of Quito report of the fetid smell of the waters which descend sometimes from the sides of the volcanos during great eruptions.

Struck with the novelty of these phaenomena, which we only mention here, the Spanish Conquistadores have, since the sixteenth century, distinguished two sorts of volcanoes,--the fire volcanos and the water volcanos (volcanes de fuego y de agua).

This last denomination, which one might say was invented to bring near to each other the volcanists and the neptunists, and to put an end to the famous schism of dogmatical geology, has been applied especially to the mountains of Guatimala and of the Archipelago of the Philippines.

The Volcan de agua, placed between the volcano of Guatimala and that of Pocaya, ruined, by torrents of water and stones which it sent forth the 11th of September 1541, the town of Almolonga, which is the ancient capital of the country.

This mountain does not attain the limit of perpetual snow, but it remains covered with snow several months of the year.

When we call to mind the confusion of the accounts that are found in our own days in the public papers of Europe, every time that AEtna or Vesuvius are in action, we cannot complain of the uncertainty in which the chroniclers of Spanish America and the Conquistadores of the sixteenth century leave us respecting the phaenomena of volcanic inundations, so worthy of engaging the attention of natural philosophers.

During the eruption of AEtna in 1792, there opened on the declivity of the volcano, 3 miles from the crater, a gulf from which issued for several weeks water mixed with ashes, scoriae, and clays.

These liquid ejections, which must not be confounded with the phaenomenon of the Salses , or air volcanos, were very thick.

It is easily conceivable that, in the equinoctial zone, even very low mountains may by a particular disposition of their subterraneous cavities, and by the excessive abundance of the tropical rains, be subject to cause frightful inundations each time that they undergo shocks of earthquakes.

Furthermore, the phaenomena which we have been describing are repeated from time to time far from the volcanos, in secondary mountains, in the centre of Europe.

Sad examples have proved in our days that in the Alps of Switzerland, where no shocks of earthquakes are felt, a simple hydrostatic pressure lifts up and breaks with violence banks of rock, throwing them to a great distance, as if they were projected by elastic forces.

Juarros, Compendio de la Historia de Guatemala, 1809, t. i. p. 72; t. ii. p. 351. -- Remesal, Hist.

de la Provincia de San-Vicente, lib. iv. cap. 6.-- Also in the great eruption of the volcano of the province of Sinano in Japan (July 27, 1783), boiling waters were mixed with the rapilli.

(Memoire sur la Dynastie regnante des Djogouns.

1820, p. 182.)

Ferrara, Descr. dell' Etna, p. 132.

As this phaenomenon seems to have some relation to that of the Moya de Pelileo, which contains the carburets of hydrogen, and which I made known at my return from America, I obtained very lately an explanatory manuscript note from the learned Sicilian geologist, M. Ferrara, on the muddy eruption of AEtna observed March 25, 1792.

There is only the muddy torrent (fiume di fango) of Santa-Maria- Nascemi (March 18, 1790), in the Val di Noto, which seems to me to belong to the action of the Salses.

The trachytes of Purace contain sulphur like those of Mont- Dore in Auvergne, of Budoshegy in Transylvania, of the Isle of Montserrat in the Little Antilles, and of the Antisana in the Andes of Quito.

It is still formed daily in the clefts around the gulfs of Purace, either by a very slow sublimation, or by the contact of the sulphurous acid vapours with the sulphuretted hydrogen of the lake.

The volcano labours in its interior like the solfataras; but it presents nothing in its form that resembles the places which are designated by that name, and which I have visited; for example, the solfataras of Puzzuoli, the Peak of Teneriffe, and the volcano of Jorullo in Mexico.

These last three are craters which have vomited lava; they show that their first state was very different to that in which we see them at present.

With very elevated temperatures, the chemical products of a volcano are not the same as with a very low temperature.

If the appellation solfatara be given indefinitely to every place where sulphur is formed or deposited, this denomination may also be applied to a district which I shall describe here, and which contrasts singularly with the trachytes of volcanos.

In crossing the Cordilleras of the Andes of Quindiu, between the basins of the Cauca and of the Magdalena (lat. 4° 50'--4° 45') I saw an immense formation of gneiss and of micaceous schist resting immediately on an ancient granite.

The layers of micaceous schist which alternate with strata of gneiss are free from garnets, whilst the gneiss contains many.

But, in these same primitive micaceous schists, a little to the west of the station of the Moral, at the height of 6800 feet above the level of the sea, in the Quebrada del Azufral, some decayed veins extremely full of crevices abound in sulphur, and exhale a sulphureous vapour, the temperature of which rose to 47°8 centesimal (118° F.), when the surrounding air was at 20°2 (68° F.) Here then is repeated on a small scale, in the clefts of a primitive rock, the phaenomena of the trachytic solfatara of Budoshegy in Transylvania, which has been recently examined by M. Boue.

The micaceous schist of Quindiu, which surrounds the open veins, is decomposed, and the sulphur is formed in masses considerable enough to become the object of a sulphur-work which supports a family settled in the ravine of the Azufral.

The rock contains some decomposed pyrites; but I much doubt whether these pyrites perform the important part in nature which has been so long ascribed to them in geological treatises.

In the midst of the granitic rocks of Quindiu rise the trachytes of the volcano of Tolima, a truncated cone, which reminds us of the form of the Cotopaxi, and which, according to a geodesic measurement made by me at the west of Ibague, is the highest summit of the Andes in the northern hemisphere . A rivulet which emits considerably the smell of sulphuretted hydrogen descends from the Peak of Tolima, and proves that the trachytes which have penetrated the granitic rocks also contain sulphur.

Two learned travellers, MM. Rivero and Boussingault, have recently visited this little solfatara in the micaceous schist of Quindiu: they have sent some specimens to the cabinet of the Ecole des Mines at Paris, which contains the most complete and instructive series of geognostic specimens.

Following the Cordillera of the Andes southwards, these same alternations of primitive formations and of porphyritic and trachytic regions are found:--but what was my surprise, when beyond the equator I ascertained that the celebrated mountain of sulphur of Ticsan (S. lat. 2° 10'), between Quito and Cuenca, is neither composed of trachyte, nor of chalk or of gypsum, but of micaceous schist.

See my Barometric and Geognostic Levelling of the Cordilleras, No. 102.

Height 18,321 feet; N. lat. 14° 46'.

This mountain of sulphur, which the Indians call Quello, is situated, according to my barometric measurement, at the height of 8000 feet above the level of the ocean.

It is entirely composed of primitive micaceous schist (glimmerschiefer), which is not even anthracitic, as are the varieties of this rock peculiar to transition countries.

In some very deep ravines between Ticsan and Alausi, the micaceous schist is seen resting on gneiss.

The sulphur is contained in a stratum of quartz which is more than 1200 feet thick: it lies in a tolerably regular direction N. 18° E., and inclined like the micaceous schist from 70° to 80° to the north west. The bed of quartz, which passes sometimes into the hornstone, is wrought in an open working.

The declivity of the Cerro Quello, on which the works were begun some centuries since, is opposite to the south-south-east; and the bed of quartz appears to be prolonged towards the north-north-west, that is to say, towards the coast of the Pacific Ocean. It is however asserted that sulphur has not been found on the surface of the ground in this direction to the distance of 2000 toises from Ticsan.

All is covered there with a thick vegetation.

Towards the end of the eighteenth century, masses of sulphur were still worked, which were from 2 to 3 feet in diameter.

At present they are working some quartzose strata much less rich, in which the sulphur is only dispersed in nodules from 3 to 4 inches thick.

It is observed that the quantity of sulphur increases with the depth; but the working has been so unskilfully directed that the lower strata are nearly inaccessible.

The quartz in which the sulphur is dispersed presents neither great fissures nor cavities, or druses; nor have I been able to find any specimen of crystallized sulphur.

The mineral which is the object of the working of the Cerro Quello does not form a mass or complication of veins, as might be supposed: the sulphur is disseminated without any continuity by little masses in the quartz which traverses the micaceous schist in a direction parallel to its strata.

The clefts that have perhaps formerly united these masses are no longer visible, but all the quartz seems to have undergone an extraordinary change.

It is tarnished, often brittle, and breaks in some parts on the least shock; which indicates an imperceptible cleavage.

The temperature of the rock did not differ from that of the exterior air.

The inhabitants like to attribute the violent earthquakes to which their country has been sometimes exposed to concavities which they suppose to exist under the mountain of sulphur.

If this hypothesis be well founded, it must be admitted that the cause which it indicates acts but locally.

In the great catastrophe of the 4th of February 1797, which destroyed so many thousand Indians in the province of Quito,--the three places where there is the most sulphur, the Cerro Quello; the Azufral of Cuesaca near to the Villa of Ibarra, and the Machay of Saint- Simon, near the volcano of Antisana, were but very feebly agitated; but at a much earlier period there has been experienced, even on the bed of quartz which includes the sulphur near Ticsan, an explosion similar to that of a mine.

The bed of quartz appears at the surface on the two sides of the little river of Alausi; and facing the Cerro Quello is found a little plain, where, in the seventeenth century, was situated the village of Ticsan.

The ruins of the church of Pueblo Viejo are still seen.

An earthquake wholly local (for its effects were confined to a very small space of country) made the surrounding hills sink down: a part of the village sunk; another part was thrown into the air, as happened at Riobamba, where I found the bones of the unfortunate inhabitants of the town thrown on the Cerro de la Culca, to a height of several hundred feet.

The Indians of Ticsan who survived this catastrophe constructed their habitations more to the north, far from the mountain of sulphur whose neighbourhood they dreaded.

It may be that the coincidence of these phaenomena of explosion and of the position (gisement) of a substance easy to be converted into elastic vapours has only been accidental:

but it may be also that ancient communications with the interior of the globe, those upon which is formed by sublimation the immense deposit of sulphur, become re-established from time to time, and allow the volcanic forces to shake the surface of the soil.

Near the ruins of Pueblo Viejo of Ticsan I found a hill of gypsum lying above the micaceous schist: as this hill is not covered by other formations, it is difficult to decide whether the gypsum, partly fibrous and mixed with clay, is primitive, like that of Val Canaria, or transition, like the gypsum of the Tarentaise.

The abundance of sulphur in primitive countries is a very important geological fact, in relation to the study of volcanos and of rocks through which the subterraneous fire has opened itself a passage.

Before I had visited the Andes of Quito and the mountain of Ticsan, sulphur was known only in the transition limestone and gypsum; in the gypsums, marles and muriatiferous clays of secondary countries, and in the rocks exclusively called volcanic.

These different geological situations, to which may be added the tertiary districts, very ill explained the frequency of the sulphureous vapours exhaled by the mouths of the volcanos whose centre of action was placed (and doubtless with propriety) very much below the secondary and intermediate rocks.

In proportion as we become acquainted with a greater part of the globe we not only see positive geognosy, that is to say, the view of the formations and of the geological positions, extended; but even geogony, or systematic geognosy, the conjectural science which investigates the causes of phaenomena, begins to be founded on the analogy of more certain facts.

We may have been struck for some time past with the little masses of native sulphur which are disseminated in some metalliferous veins, and which traverse granitic rocks; for example, in Schwarzwald, near Riepoldsau.

The mountain of Ticsan which I have made known, leaves no further doubt respecting the existence of sulphur in the primitive districts.

It has also been lately found in Brazil, that the chloritic quartz formation which covers, in the Capitania de Minas Geraes, the primitive clay-slate, contains both gold and sulphur.

Laminae of this rock strongly heated burn with a blue flame.

Near to Villarica, in the district called Antonio Pereira, a schist, of the same age as that on which is superposed the itacolumite or chloritic quartz, contains a calcareous bed traversed by veins of quartz, which the Baron d'Eschwege (director of the gold and diamond mines of these countries) has found filled with little nodules of pulverulent sulphur.

All these phaenomena increase in interest, when we reflect that this learned geologist, and also another German traveller (M. Pohl) incline to the opinion that gold, micaceous iron, diamonds, euclases, platina, and palladium, which are peculiar to the alluvial districts of Brazil, have been derived either from the destruction of the great formation of chloritic quartz, or from that of a ferruginous bed (itabarite) which is placed above this formation.