THE

Boston Journal

OF

PHILOSOPHY AND THE ARTS.

ART. LIV.-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 Phenomena which are exhibited by Sulphur, Sulphuretted Hydrogen, in Water, in Volcanos. By M. A. DE HUMBOLDT. [Phil. Mag.] (Concluded from p. 466.)

THE good curate of the village of Puracé 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 phenomenon, 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 sunmit 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 tradi tions about boiling waters that issued from the crater of Vesuvius in 1631; fabulous traditions, which are perpetuated by an inscription at Portici.

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. The 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

* M. de la Condamine (Mémoires de l'Académie 1754, p. 18) had already expressed very precise ideas on the cause of these phenomena, which are found equally weil 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 phenomena by M M. Monticelli and Covelli. (Storia del Vesuvio degli anni 1821-23, p. 91–98) Phil. Mag, vol. Ixiii, p. 46. By the mixture of the rain and the volcanic cinders, there is formed in the air (1. 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.

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 more frequently pure water, which does not act at all on the most sensible re-agents; at other times they contain muriatic acid. It is remarkable 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 Etna of March 23, 1536, and March 6, 1755, the sudden melting of the banks of snow produced great devastations.*

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 (Codazales) 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 Puracé, 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 phoenomena, which we only mention here, the Spanish Conquistadores have, since the sixteenth century, distinguished two sorts of volcanos,-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 dog-matical

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

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 Guatamala,* 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 Etna 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 phoenomena of volcanic inundations, so worthy of engaging the attention of natural philosophers. During the eruption of Etna in 1792, there opened on the declivity of the volcano, three miles from the crater, a gulf, from which issued for several weeks water mixed with ashes, scoriæ, and clays. These liquid ejections, which must not be confounded with the phoenomenon 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 phoenomena 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 rocks, throwing them to a great distance, as if they were projected by elastic forces.

The trachytes of Puracé contain sulphur like those of Mont

* Juarros, Compendio de la Historia de Gautemala, 1809, t. i. p. 72; t. ii. p. 351. Remesal. Hist. de la Provincia de San Vincente, 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. Mémoire sur la Dynastie regnante des Djogouns, 1820, p. 182.

Ferrara, Descr. dell' Etna, p. 132. As this phenomenon seems to have some relation to that of the Maya 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 Etna, 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 actions of the Salses.

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 Puracé, 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 ba-. sins 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' centessimal (118° F.), when the surrounding air was at 20° (68° F.) Here then is repeated on a small scale, in the clifts of a primitive rock, the phenomena of the trachytic solfatara of Budoshegy in Transylvania, which has been recently examined by M. Bouè. 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,

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