Digitale Ausgabe

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I had made known, at the time of my return from America,the presence of the sulphuric and muriatic acids in the waterof the Rio Vinagre, which the aborigines call Pusambio (SeeViews of the Cordilleras, and Monuments of the People ofAmerica, 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 theydeparted for Bogota, to verify these facts. The analysis, whichwe owe to one of these expert chemists, is the first which hasbeen attempted on the water of the Rio Vinagre. I shall givesome extracts from the journal of my travels, in great part stillunpublished, explanatory of the local circumstances. The town of Popayan is situated in the beautiful valley ofthe Rio Cauca, on the Bogota road to Quito, at the foot ofthe two great volcanos of Puracé and Sotarà. These volca-nos, almost extinct, and exhibiting only the phænomena ofsolfataras, form part of the central chain of the Andes of NewGranada. At 1° 55′ and 2° 20′ of north latitude, the groupof mountains which incloses the sources of the Magdalena isdivided into three branches, of which the eastern is continuedtowards Timana and the Nevados of Chita and of Merida;the intermediate and central one towards the Paramos ofGuanacas and of Quimdiù; the western towards the platini-ferous district of the Choco and the isthmus of Panama. Inascending from the town of Popayan to the summit of thevolcano of Puracé, M. Bompland and I found at the heightof 8672 feet a little plain (Llano del Corazon), inhabited bypoor Indian husbandmen. This plain is separated from therest of the acclivity, with which it would otherwise be con-tinuous, by two ravines extremely deep: it is at the edge ofthese precipices that the village of Puracé is built. Springsrise every where from the trachytic rock; each garden is sur-

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* It cannot be doubted that the indications are by grammes and fractionsof grammes: a litre of the water of the Rio Vinagre includes 1·080 grammeof sulphuric acid and 0·184 gramme of muriatic acid. This proportionof sulphuric acid, is nevertheless very sensible to the taste, and is mani-fested by an abundant precipitate with the salts of barytes.[The litre being 2·113 pints, the contents of the water in English grainswill be as follows: sulphuric acid 16·68; muriatic acid 2·84; alumine3·7; lime 2·47.–Edit.]|110| rounded with a quickset hedge of narrow-leaved euphorbium(lechero) of the most delicate green. This beautiful verdurecontrasts in a striking manner with the back-ground of blackand arid mountains which surround the volcano, and whichare rent by the effects of the earthquakes. The site of the village is celebrated in the country on accountof three beautiful cascades (choreras) of the river of Pusambio,whose water is acid, and which the people, who know no otheracid than vinegar, call Rio Vinagre, sometimes Gran Vinagre.This river takes its rise at the height of nearly 10,871 feet, ina very inaccessible spot. Although the temperature of thewater be little different in the lower cascades from that of thesurrounding atmosphere, it is not less certain that the sourcesof the Rio Pusambio or Vinagre are very hot. This fact wasattested to me by the natives and by the missionary of thevillage of Puracé. In going to the summit of the volcano Isaw a column of smoke rise at the place where the acid watersmake their appearance. I have drawn the second of the fallsof the Vinagre (plate xxx. of the Views of the Cordilleras):the water, which opens itself a passage across a cavern, isprecipitated more than 383 feet in depth. The fall has a verypicturesque effect; but the inhabitants of Popayan would bebetter pleased if the river, instead of throwing itself into theRio Cauca, became engulfed in some other crevice; for suchis the delicacy of constitution of animals which breathe bygills, and which absorb the oxygen dissolved in the water, thatthe Cauca during a course of four leagues is destitute of fish,on account of the mixture of its waters with those of the RioVinagre*, which are charged both with oxide of iron and withsulphuric and muriatic acid. After staying a considerabletime on the craggy wall of rock which borders the cascade,a pricking sensation is felt in the eyes from the minute sprayin the atmosphere. Fish re-appear in the Rio Cauca at thepoint where it becomes enlarged by the influx of the Pinda-mon and of the Palacé†. A little to the north of the sources of the Pusambio risetwo other rivulets charged in like manner with free sulphuricacid, which the people call the Little Vinegars (los dos Vinagreschicos): they throw themselves into the Rio de San Francisco,which is itself but a tributary of the Gran Vinagre. Duringmy stay at Popayan, it was an opinion generally receivedthat all these acid waters contained some iron dissolved by a

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* M. Caldas has even attributed to this mixture, doubtless with littlereason, 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.|111| great quantity of carbonic acid. When it was merely remem-bered that the sources of the Vinagre are very hot, this opinionought to have been abandoned. I boiled some water takenfrom the cascade; and I found, after the ebullition, the sameacid 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 wasshown by the prussiate of lime, that of lime by the oxalate ofpotash. When the water was weighed with great care in theoffice of the mint of Popayan, the weight of an equal quantityof the water of the Vinagre was found to be to that of distilledwater as 2735\( \frac{1}{2} \) gr. to 2731 gr.; that is to say, that the specificgravity of the water of the cascade was 1,0015. The waters which I describe, and of which M. Rivero hasgiven the first analysis, must not be confounded with those ofthe two subterraneous lakes which we have found near the sum-mit of the volcano; one is 14,356 feet high, the other, abovethe snows, 15,475 feet. This volcano of Puracé is a dome ofsemivitreous trachyte, of a blueish grey and having a conchoidalfracture. It does not present a great crater at its summit,but several little mouths. It differs very much from theneighbouring volcano, the Sotarà, 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 ortears of obsidian, the surface of which is often tubercular.They present, what I have seen nowhere else in the two hemi-spheres, all the shades of colour, from deep black to that of anartificial glass entirely colourless. It may appear surprisingto see that this deprivation of colour has not been accompaniedby any inflation or porosity. The obsidians of Sotarà aremixed with fragments of enamel which resemble the porcelainof Réaumur, and adhering to which I have found masses offelspar which have resisted fusion. Here, as in the Andes of Quito, as at Mexico and at theCanary Islands, the system of basaltic rocks lies far from thetrachytes which form the volcanos of Puracé and of Soltarà.The basalts of the Tetilla of Julumito belong only to the leftbank of the Cauca. They rise from transition porphyries freefrom augite, containing some hornblende, a very little quartzin small crystals embedded in the mass, and a felspar whichpasses from the common to the vitreous variety. This por-

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* The conjoint presence of the sulphuric and muriatic acids has alsobeen observed by M. Vauquelin in the water which M. Leschenault hadtaken from the crater-lake of Mount Idienne in Java (Journal de Phy-sique, t. lxv. p. 406.) See Phil. Mag. vol. xlii. pp. 126, 182.|112| phyry is covered, near to Los Serillos, with a blackish-graylime-stone traversed by veins of carbonate of lime, and so muchovercharged with carbon that in some parts it stains the fingerslike an aluminous schist, or like the lydian * stone of Stee-ben in the Fichtelgebirge. The trachytic dome of Puracéwhich gives birth to the little river of sulphuric acid, rises outof a porphyritic syenite (with common felspar), which in itsturn is superposed on transition granite abounding in mica.This observation †, very important for the position of volcanicrocks, may be made near to Santa Barbara in ascending fromPopayan to the village of Puracé. The volcano, like the mostpart of the great volcanos of the Andes, presents layers ormantles 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 havebeen thrown up through crevices which have since becomeclosed. They are like those of the Fosso Grande of Vesuvius,which owe their granular texture to volcanic fire. It is notpossible to go on horseback further than the cascades of theRio Vinagre. From thence we were eight hours in mountingon foot to the summit of the volcano and in descending fromit. The weather was dreadful; snow and hail fell. I had agreat deal of difficulty in lighting the tinder at the point ofthe conductor of Volta’s electrometer; the balls of elder-pithseparated from 5 to 6 lines, and the electricity passed oftenfrom positive to negative without there being any other symp-tom of storm: for thunder and lightning are (according to myexperience) generally very rare when we are above 12,800 or14,000 feet high. The hail was white ‡; the hailstones, fromfive to seven lines in diameter, composed of layers varying intranslucency. They were not only much flattened towards thepoles, but so much increased in their equatorial diameter,that rings of ice separated themselves on the least shock. I

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* M. Vauquelin has recently proved by a direct analysis the presenceof carbon in the purest lydian stones. I had found, in a series of experi-ments made on the galvanic exciters in 1798, that the lydian stones of thetransition schists of Steeben produced jointly with zinc the same effect asgraphite or carburet of iron. I have since made some trials to prove che-mically the presence of carbon in several varieties of lydian stone.—Seemy Experiments on the Nervous and Muscular Fibre (in German), t. ii.pp. 163.† See an account of the whole of these phænomena of the volcanos ofPopayan 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 Paramode Guanacas, where the road from Bogota to Popayan passes to the heightof 14,700 feet, there has been seen fall, not snow, but red hail. Did it inclosethose same germs of vegetable organization which have been discoveredabove the polar circle?|113| had already twice observed and described this phænomenon, inthe mountains of Bareuth, and near Cracow, during a journey inPoland. Can it be admitted that the successive layers which areadded to the central nucleus are in a state of fluidity so great thatthe rotary motion can cause the flattening of the spheroids? When the barometer indicated that we were come very nearthe limit of perpetual snow, we found the masses of sulphurdisseminated in imperfectly columnar trachytic rocks aug-mented. This phænomenon struck me the more, as I knewhow rare sulphur is on the sides of inflamed volcanos:—a co-lumn of yellowish smoke and a frightful noise informed us ofthe neighbourhood of one of the mouths (bocas) of the volca-no. We had some trouble to approach its edge; the declivityof the mountain being very steep, and the crevices only coveredby a crust of sulphur, of whose thickness we were ignorant. Webelieved we might rate the extent of this crust, which is ofteninterrupted by rocks, at more than 12,000 square feet. Theselittle ridges of trachytic rocks act strongly on the magnet. I triedto keep at as much distance from them as possible, to determinethe inclination of the needle. It was at the town of Popayan(height 5825 English feet) 23°,05, centesimal division; at thevillage of Puracé (height 8671 feet) 21°,81; near the summit ofthe volcano of Puracé (height 14,542 feet) 20°,85. The in-tensity of the magnetic force varied very little at Popayan andat the village of Puracé; and the diminution of the inclinationis certainly not the effect of the height, as is proved by somany other observations which I have made on the summit ofthe Andes, but the effect of local attractions depending oncertain centres of action in the trachytes. The mouth of the volcano of Puracé is a perpendicularcleft, the visible opening of which is only 6 feet long and 3broad. It is covered in form of a vault by a layer of verypure sulphur, which is 18 inches thick, and which the force ofthe elastic vapours has split on the north side. At the distanceof 12 feet from the mouth we felt an agreeable heat. The cen-tigrade 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 of14,356 feet), rose to 15° (61° F.). Placed in such a manner asnot to be incommoded by the vapours, we had the pleasure ofdrying our clothes. The frightful noise which is heard nearthis opening has almost always the same intensity: it canonly be compared to that which would be caused by severalsteam-engines together, were the dense steam suffered toescape from all at the same moment. We threw great stonesinto the crevice, and we discovered on this occasion that the|114| opening communicated with a basin full of boiling water.The vapours which escape with so much violence are of thesulphurous acid, which is indicated by their suffocating smell.We shall soon see that the water of the subterraneous lakeis charged with sulphuretted hydrogen; but the odour of thisgas is not smelt at the summit of the volcano, because it isdisguised by the much stronger smell of the sulphurous acidvapours. I had not any means of determining the tempera-ture of these vapours, which seem to undergo a prodigiouslystrong pressure in the interior of the volcano. As the Indianspretend that the opening has several compartments which arenot all filled with water, and that the noise which is heard attimes in the interior of the crevice is the forerunner of flames,I introduced, by means of a long pole, some papers colouredwith the tincture of violet, under the vault, where I could besure of not touching the surface of the water. Drawing backthe pole, I found the papers strongly reddened, but not at allinflamed, as was easy to be foreseen. We suceeded after several vain attempts in obtaining somewater from the crevice: this was by tying a tutuma (the fruit ofthe Crescentia Cujete) to a stick 8 feet long. The water wasdirectly poured into a bottle hermetically stopped. We ex-amined it on our return to the village of Puracé: it exhaled astrong smell of sulphuretted hydrogen; it had no acid taste,but some weak precipitates caused by the nitrate of silvershowed the presence of muriatic acid. The crust of sulphurwhich forms above the mouth arises without doubt from thecontact of the vapours of sulphurous acid with the sulphurettedhydrogen which the subterraneous lake disengages. Even thewater of this lake is covered with a coat of sulphur, which dis-appeared in the places where we threw the stones. It resultsfrom these observations, that only the presence of the muriaticacid, or of combinations of this acid with salifiable bases, indi-cates a feeble analogy between the waters of Rio Vinagre andthose of the lakes. The first, which spring much lower, at thedeclivity of the volcano of Puracé, are charged with free sul-phuric acid: the others, which are found at the summit of thevolcano, contain sulphuretted hydrogen. As the upper mouthsare found at very different heights above the level of the sea,it may be supposed that their subterraneous waters are owingto the melting of the snows, and that they do not communicate.The Rio Vinagre receives its acid in the interior of a volcanowhich abounds in sulphur, and the temperature of which ap-pears extremely elevated, although for centuries no luminousphænomenon has been perceived at its summit. |115| The good curate of the village of Puracé thought to rendera great service to his parishioners, as well as to the inhabitantsof the town of Popayan, in causing, as he said, the chimneysof the volcano to be cleaned now and then. He ordered theIndians to take away the crust of sulphur which rises in formof a dome above the crevice. This crust has acquired some-times, as they affirm, a thickness of as much as four feet inless than two years. It lessens without doubt the opening bywhich the vapours of sulphurous acid escape; but it may beconceived 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 commotionsby acting against the rocky sides of the volcano. For severalyears the lakes, which represent in miniature the crater-lakesof our extinguished volcanos, seem each to preserve the samelevel of their line of water; which proves that the evaporationis 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 inun-dations. I dwell on this phænomenon, because it seems tothrow some light on a problem of the geology of volca-nos, which has not been sufficiently examined: I mean theejections of water and mud. At Vesuvius these ejectionsare only apparent, and come neither from the interior of thecrater nor from the lateral crevices. An immense electrictension manifests itself in the atmosphere which surroundsthe summit of the volcano at the time of great eruptions.Flashes of lightning cleave the air; the aqueous vapoursthrown out by the crater are cooled; thick clouds envelop thesummit during the continuance of this storm, confined to alittle space; the water descends in torrents, and is mixed withthe tufaceous substances which it drags with it *. These ef-fects, purely meteorological, have given rise to the traditionsabout boiling waters that issued from the crater of Vesuvius

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* M. de la Condamine (Mémoires de l’Académie 1754, p. 18) had alreadyexpressed very precise ideas on the cause of these phænomena, which arefound equally well explained in the Storia dell’ incendio del 1737, publishedby the Academy of Naples. I saw in my last journey to Naples, (December1822,) 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 onlymud, but masses of lava 48 feet in circumference and 25 feet high. Seethe excellent description of these phænomena by MM. Monticelli andCovelli. (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 cin-ders, there is formed in the air (l. c. p. 94) a kind of pisolites with concen-tric layers, which I also found on the plain of Hambato, among the ancientejections of the Carguairazo. The inhabitants of the province of Quitocall these pisolites earth hailstones.|116| in 1631; fabulous traditions, which are perpetuated by an in-scription at Portici. In the volcanos of the Andes which exceed the limit of per-petual snow, the causes of inundations are very different fromthose which we have just indicated. As the eruptions ofthese colossal summits take place only after long intervals(every thirty or forty years, or still more rarely), banks of snowof an enormous thickness accumulate on the sides of the moun-tains. These snows do not melt at the time of the explosiononly, but sometimes several days before. Thus in February1803, during my stay at Guayaquil, the inhabitants of theprovince of Quito were frightened at the appearance of thecone of Cotopaxi, which lost a great part of its snows ina single night, and showed plainly the black colour of itsburnt rocks. Whatever idea may be formed of the powerof the volcanic forces, and of the intensity of the subterraneousfires in the Andes, it cannot be admitted that the thick sidesof a cone could be uniformly warmed, and transmit the heatwith such rapidity (by the conductibility of their mass) to theoutside. The sudden melting of the snows, when, in the Cor-dilleras, it precedes the eruptions, is probably owing only toan infinity of little fumaroles which disengage hot vapoursthrough the fissured rock of the cone. These vapours, accord-ing to what I have had opportunity of observing in the cra-ters of Vesuvius, the Peak of Teneriffe, and the volcano ofJorullo in Mexico, are most frequently pure water, whichdoes not act at all on the most sensible re-agents; at othertimes they contain muriatic acid. It is remarked that thesame crevice gives, at very near epochs, distilled (pure) waterand very acid waters. The artificial spring which M. Gim-bernat has had the ingenious idea of forming at the sum-mit of Vesuvius, by the condensation of the vapours in a glasstube, has sometimes shown these variations: they prove eitherthe change of chemical action in the interior of the volcano,or the accidental opening of some new communications. Inthe Andes of Quito, as in Iceland, and in the eruptions ofÆtna of March 23, 1536, and March 6, 1755, the suddenmelting of the banks of snow produced great devastations*. At other times, by slow infiltrations the snow waters are ac-cumulated in the lateral cavities of the volcano; shocks ofviolent earthquakes, which do not always coincide with theepoch of the fiery eruptions, open these cavities; and waterslong kept in, which support little fish of the genus Pimelodes,carry with them pulverized trachytes, pumice-stones, tufas,

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* Ferrara, Campi Flegrei, 1810, p. 165.—Idem, Descriz, dell’ Etna, 1818,p. 89, 116—120.|117| and other incoherent matters. These liquid ejections spreadsterility over the plains for centuries. Muddy clays (lodazales)covered a space of more than four square leagues, when, inthe night of the 19th of June 1698, the Peak of Carguai-razo, the actual height of which exceeds 15,700 feet, sunkdown with a noise. The lakes of sulphureous water that wefound at the summit of Puracé, explain what the inhabit-ants of Quito report of the fetid smell of the waters which de-scend sometimes from the sides of the volcanos during greateruptions. Struck with the novelty of these phænomena,which we only mention here, the Spanish Conquistadores have,since the sixteenth century, distinguished two sorts of volca-noes,—the fire volcanos and the water volcanos (volcanes defuego y de agua). This last denomination, which one mightsay was invented to bring near to each other the volcanists andthe neptunists, and to put an end to the famous schism ofdogmatical geology, has been applied especially to the moun-tains 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 stoneswhich it sent forth the 11th of September 1541, the town ofAlmolonga, which is the ancient capital of the country. Thismountain does not attain the limit of perpetual snow, but itremains covered with snow several months of the year. Whenwe call to mind the confusion of the accounts that are foundin our own days in the public papers of Europe, every timethat Ætna or Vesuvius are in action, we cannot complain ofthe uncertainty in which the chroniclers of Spanish Americaand the Conquistadores of the sixteenth century leave us respect-ing the phænomena of volcanic inundations, so worthy of enga-ging the attention of natural philosophers. During the eruptionof Ætna in 1792, there opened on the declivity of the volcano,3 miles from the crater, a gulf† from which issued for se-veral weeks water mixed with ashes, scoriæ, and clays. Theseliquid ejections, which must not be confounded with the phæ-

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* 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 inJapan (July 27, 1783), boiling waters were mixed with the rapilli. (Mémoiresur la Dynastie régnante des Djogouns. 1820, p. 182.)† Ferrara, Descr. dell’ Etna, p. 132. As this phænomenon seems tohave some relation to that of the Moya de Pelileo, which contains the carbu-rets of hydrogen, and which I made known at my return from America, Iobtained very lately an explanatory manuscript note from the learned Si-cilian geologist, M. Ferrara, on the muddy eruption of Ætna observedMarch 25, 1792.|118| nomenon of the Salses *, or air volcanos, were very thick.It is easily conceivable that, in the equinoctial zone, even verylow mountains may by a particular disposition of their sub-terraneous cavities, and by the excessive abundance of thetropical rains, be subject to cause frightful inundations eachtime that they undergo shocks of earthquakes. Furthermore,the phænomena which we have been describing are repeatedfrom time to time far from the volcanos, in secondary moun-tains, in the centre of Europe. Sad examples have provedin our days that in the Alps of Switzerland, where no shocksof earthquakes are felt, a simple hydrostatic pressure lifts upand breaks with violence banks of rock, throwing them to agreat distance, as if they were projected by elastic forces. The trachytes of Puracé contain sulphur like those of Mont-Dore in Auvergne, of Budoshegy in Transylvania, of theIsle of Montserrat in the Little Antilles, and of the Anti-sana in the Andes of Quito. It is still formed daily in theclefts around the gulfs of Puracé, either by a very slow subli-mation, or by the contact of the sulphurous acid vapourswith the sulphuretted hydrogen of the lake. The volcano la-bours in its interior like the solfataras; but it presents nothingin its form that resembles the places which are designated bythat name, and which I have visited; for example, the solfa-taras of Puzzuoli, the Peak of Teneriffe, and the volcanoof Jorullo in Mexico. These last three are craters whichhave vomited lava; they show that their first state was verydifferent to that in which we see them at present. With veryelevated temperatures, the chemical products of a volcano arenot the same as with a very low temperature. If the appella-tion solfatara be given indefinitely to every place where sul-phur is formed or deposited, this denomination may also beapplied to a district which I shall describe here, and whichcontrasts singularly with the trachytes of volcanos. In cross-ing the Cordilleras of the Andes of Quindiu, between the ba-sins of the Cauca and of the Magdalena (lat. 4° 50′—4° 45′)I saw an immense formation of gneiss and of micaceous schistresting immediately on an ancient granite. The layers ofmicaceous schist which alternate with strata of gneiss are freefrom garnets, whilst the gneiss contains many. But, in thesesame primitive micaceous schists, a little to the west of thestation of the Moral, at the height of 6800 feet above thelevel of the sea, in the Quebrada del Azufral, some decayed veins

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* 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 belongto the action of the Salses.|119| extremely full of crevices abound in sulphur*, and exhale a sul-phureous vapour, the temperature of which rose to 47°8 cen-tesimal (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 primitiverock, the phænomena of the trachytic solfatara of Budoshegyin Transylvania, which has been recently examined by M.Bouè. The micaceous schist of Quindiu, which surrounds theopen veins, is decomposed, and the sulphur is formed in massesconsiderable enough to become the object of a sulphur-workwhich supports a family settled in the ravine of the Azufral.The rock contains some decomposed pyrites; but I muchdoubt whether these pyrites perform the important part innature which has been so long ascribed to them in geologicaltreatises. In the midst of the granitic rocks of Quindiu risethe trachytes of the volcano of Tolima, a truncated cone, whichreminds us of the form of the Cotopaxi, and which, accordingto a geodesic measurement made by me at the west of Ibagué,is the highest summit of the Andes in the northern hemi-sphere †. A rivulet which emits considerably the smell ofsulphuretted hydrogen descends from the Peak of Tolima,and proves that the trachytes which have penetrated thegranitic rocks also contain sulphur. Two learned travellers,MM. Rivero and Boussingault, have recently visited this littlesolfatara in the micaceous schist of Quindiu: they have sentsome specimens to the cabinet of the Ecole des Mines at Paris,which contains the most complete and instructive series of geo-gnostic specimens. Following the Cordillera of the Andes south-wards, these same alternations of primitive formations and ofporphyritic and trachytic regions are found:—but what was mysurprise, when beyond the equator I ascertained that the cele-brated mountain of sulphur of Ticsan (S. lat. 2° 10′), betweenQuito and Cuenca, is neither composed of trachyte, nor ofchalk or of gypsum, but of micaceous schist. This mountain of sulphur, which the Indians call Quello, issituated, according to my barometric measurement, at theheight of 8000 feet above the level of the ocean. It is entirelycomposed of primitive micaceous schist (glimmerschiefer),which is not even anthracitic, as are the varieties of this rockpeculiar to transition countries. In some very deep ravinesbetween Ticsan and Alausi, the micaceous schist is seen rest-ing on gneiss. The sulphur is contained in a stratum of quartzwhich is more than 1200 feet thick: it lies in a tolerably re-gular direction N. 18° E., and inclined like the micaceous

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* See my Barometric and Geognostic Levelling of the Cordilleras, No. 102.† Height 18,321 feet; N. lat. 14° 46′.|120| schist from 70° to 80° to the north west. The bed of quartz,which passes sometimes into the hornstone, is wrought in anopen working. The declivity of the Cerro Quello, on whichthe works were begun some centuries since, is opposite tothe south-south-east; and the bed of quartz appears to beprolonged towards the north-north-west, that is to say, to-wards the coast of the Pacific Ocean. It is however assertedthat sulphur has not been found on the surface of the groundin this direction to the distance of 2000 toises from Ticsan.All is covered there with a thick vegetation. Towards theend of the eighteenth century, masses of sulphur were stillworked, which were from 2 to 3 feet in diameter. At presentthey are working some quartzose strata much less rich, inwhich the sulphur is only dispersed in nodules from 3 to 4inches thick. It is observed that the quantity of sulphur in-creases with the depth; but the working has been so unskil-fully directed that the lower strata are nearly inaccessible.The quartz in which the sulphur is dispersed presents neithergreat fissures nor cavities, or druses; nor have I been ableto find any specimen of crystallized sulphur. The mineral which is the object of the working of the CerroQuello does not form a mass or complication of veins, as mightbe supposed: the sulphur is disseminated without any con-tinuity by little masses in the quartz which traverses the mi-caceous schist in a direction parallel to its strata. The cleftsthat have perhaps formerly united these masses are nolonger visible, but all the quartz seems to have undergonean extraordinary change. It is tarnished, often brittle,and breaks in some parts on the least shock; which indicatesan imperceptible cleavage. The temperature of the rockdid not differ from that of the exterior air. The inha-bitants like to attribute the violent earthquakes to which theircountry has been sometimes exposed to concavities whichthey suppose to exist under the mountain of sulphur. If thishypothesis be well founded, it must be admitted that the causewhich it indicates acts but locally. In the great catastropheof the 4th of February 1797, which destroyed so many thou-sand Indians in the province of Quito,—the three places wherethere is the most sulphur, the Cerro Quello; the Azufral ofCuesaca near to the Villa of Ibarra, and the Machay of Saint-Simon, near the volcano of Antisana, were but very feeblyagitated; but at a much earlier period there has been ex-perienced, even on the bed of quartz which includes the sul-phur near Ticsan, an explosion similar to that of a mine. The bed of quartz appears at the surface on the two sides ofthe little river of Alausi; and facing the Cerro Quello is|121| found a little plain, where, in the seventeenth century, was si-tuated the village of Ticsan. The ruins of the church of PuebloViejo are still seen. An earthquake wholly local (for its effectswere confined to a very small space of country) made the sur-rounding hills sink down: a part of the village sunk; anotherpart was thrown into the air, as happened at Riobamba,where I found the bones of the unfortunate inhabitants of thetown thrown on the Cerro de la Culca, to a height of severalhundred feet. The Indians of Ticsan who survived this ca-tastrophe constructed their habitations more to the north, farfrom the mountain of sulphur whose neighbourhood theydreaded. It may be that the coincidence of these phænomenaof explosion and of the position (gisement) of a substance easyto be converted into elastic vapours has only been accidental:but it may be also that ancient communications with the interiorof the globe, those upon which is formed by sublimation theimmense deposit of sulphur, become re-established from timeto time, and allow the volcanic forces to shake the surface ofthe soil. Near the ruins of Pueblo Viejo of Ticsan I found ahill of gypsum lying above the micaceous schist: as this hill isnot covered by other formations, it is difficult to decide whetherthe gypsum, partly fibrous and mixed with clay, is primitive,like that of Val Canaria, or transition, like the gypsum of theTarentaise. The abundance of sulphur in primitive countries is a veryimportant geological fact, in relation to the study of volcanosand of rocks through which the subterraneous fire has openeditself a passage. Before I had visited the Andes of Quito andthe mountain of Ticsan, sulphur was known only in the tran-sition limestone and gypsum; in the gypsums, marles and mu-riatiferous clays of secondary countries, and in the rocks ex-clusively called volcanic. These different geological situations,to which may be added the tertiary districts, very ill explainedthe frequency of the sulphureous vapours exhaled by themouths of the volcanos whose centre of action was placed (anddoubtless with propriety) very much below the secondary andintermediate rocks. In proportion as we become acquaintedwith a greater part of the globe we not only see positive geo-gnosy, that is to say, the view of the formations and of the geo-logical positions, extended; but even geogony, or systematic geo-gnosy, the conjectural science which investigates the causes ofphænomena, begins to be founded on the analogy of morecertain facts. We may have been struck for some time pastwith the little masses of native sulphur which are disseminatedin some metalliferous veins, and which traverse granitic rocks;for example, in Schwarzwald, near Riepoldsau. The mountain|122| of Ticsan which I have made known, leaves no further doubtrespecting the existence of sulphur in the primitive districts.It has also been lately found in Brazil, that the chloriticquartz formation which covers, in the Capitania de MinasGeraes, the primitive clay-slate, contains both gold and sul-phur. Laminæ of this rock strongly heated burn with ablue flame. Near to Villarica, in the district called AntonioPereira, a schist, of the same age as that on which is super-posed the itacolumite or chloritic quartz, contains a calca-reous bed traversed by veins of quartz, which the Baron d’Esch-wege (director of the gold and diamond mines of these coun-tries) has found filled with little nodules of pulverulent sulphur.All these phænomena increase in interest, when we reflect thatthis learned geologist, and also another German traveller(M. Pohl) incline to the opinion that gold, micaceous iron, dia-monds, euclases, platina, and palladium, which are peculiarto the alluvial districts of Brazil, have been derived either fromthe destruction of the great formation of chloritic quartz, orfrom that of a ferruginous bed (itabarite) which is placed abovethis formation.