down from the English pitching-place to Orotava, they computed to be about fifteen English miles, travelling at the rate of about three miles an hour. Mr. Glas supposes the perpendicular height of the English pitching-place to be about four English miles, and adding to that a mile of perpendicular height from it to the peak, observes, that the whole will be about five English miles, and that he is very certain he cannot be mistaken in this calculation above a mile either way; but this is merely conjectural, being founded on no solid data. Dr. Heberden, who was provided with proper instruments to ascertain its height, and has made the nicest observations at three different times, found it to be 2566 fathoms, or 15,396 English feet, above the level of the sea, which is only 148 yards less than three miles, reckoning the mile at 1760 yards; but the Chevalier de Borda, who measured the height of this mountain in the year 1776, makes it to be only 1931 toises, or 12340 English feet. Capt. Cook, in his first voyage, describes the appearance of this mountain, when viewed from the sea at sun-set, as very striking; for when the sun was below the horizon, and the rest of the island appeared of a deep black, the mountain still reflected his rays, and glowed with a warmth of colour which no painting can express. Mr. William Auderson, already mentioned, says of the peak of Teneriffe," It is cer tainly far from equalling the noble figure of Pico, one of the Western Islands, though its perpendicular height may be greater. This circumstance perhaps arises from its being surrounded by other high hills, whereas Pico stands without a rival,

Though the body of the mountain is covered with clouds, the peak is generally seen above them, quite clear, but sometimes the contrary happens, the whole body of the mountain being without a cloud, and only the summit of the peak covered with a thick white cloud, as with a cap. "This," says Dr. Heberden, " is often observed in the finest weather, and the Spaniards, on this occasion, say, "El pico tiene su sombrerillo puesto, The peak has put his little hat on ;" and the look on it as a certain sign of rain. The doctor says farther, that during the six or seven years that he lived in the villa of Orotava, where he had a continual sight of the peak, he never remembered one instance in which the prediction of rain failed. When Sir Joseph Banks visited this island, the doctor presented him with some salt which he collected at the top of the mountain, which he supposes to be the true natrum, or nitrum, of the ancients.

SECTION IV.

Volcanoes of the Isle of Bourbon.

THE face of the Isle of BOURBON or REUNION is peculiarly volcanic, and studded with masses of basaltic columns, of various forms and directions. M. Bory has given an interesting and picturesque description of these, in his "Voyage dans les quatres principales Isles des Mers d'Afrique," printed at Paris 1804, in 3 vols. 8vo. The principal summit of the volcano is allowed to retain the appellation of Mascarenhas, after the name of the Portuguese admiral by whom the island was first discovered. "The small hill,” says M. Bory, "at the basis of which we were now arrived, after so much fatigue, is about a hundred and sixty feet in height. It did not appear to us truncated, and we soon climbed it, though the sides be very steep, so as to form with the horizon an angle of more than eighty degrees. They are composed of little currents of glassy scoriæ, spongy, very light and brittle, and exteriorly of a brown colour, with metallic or red reflections from the pores. This volcanic substance is easily broken with the fingers, and reduced to brilliant dust, which resembles aventurine. From the top of the Piton we perceived, on the right and the left, parts of the circumference of two immense craters, which induced us to call this the central hill. The access of this central hill is nearly perpendicular; and on the summit is a round hole about forty fathoms in diameter, and eighty feet in depth. The bottom of this crater was filled with fragments of greyish lava, piled without any order, while the sides were very thin and much scorified on the outside; and were not covered with any sort of varnish, nor with that lava in tears or drops, which in general clothe the other vents. They are formed of confused fragments of different hard and grey lavas, compact, or porous. From some rents there arose light vapours, leaving yellow traces of sublimated sulphur, on the spots exposed to their contact. At one place, where a projecting rock formed a cornice, stopping for a while one of these cords of vapour, it was dissolved in drops of water to a considerable quantity.

"In general a very false idea is formed of volcanoes, and many works which pretend to describe them, paint them very different from what they are. If we believe many travellers, on the brink of a

crater, the eye cannot without terror penetrate the vast depth. As, before I had seen volcanoes, I was persuaded that their chief focus was not their summit, and that the substances which they eject were conveyed from a great depth, I believed that the vents of a burning mountain were immeasurable precipices. I had not yet reflected that when an eruption happens lava must remain in the interior of the crater, forming a solid bottom when the volcano ceased to burn, and which is broken by the following eruptions.

"Meanwhile we asked each other whence the sulphureous vapours could proceed, which annoyed us from time to time, and sought to guess what could produce the noise we heard, when one of our company, who had advanced towards the left, stopped short with strong signs of terror. On hearing his inarticulate cries, I imagined that he must see some extraordinary object, which he could not find words to express. The negroes around him stood petrified. I advanced, and at the sight of a wonderful spectacle very difficult to describe, I was seized with amazement in my turn, and could not explain my sensations. At cur feet, from the bottom of an elliptic abyss formed like a tunnel of vast extent, and of which the sides of burnt laya threatened a speedy ruin, issued two contiguous gerbes, or perpendicular spouts, like a Chinese tree in artificial fire-works; but here the fiery matter seemed like tumultuous waves, darted to the height of more than a hundred twenty feet, dashing against each other with a bloody light, in spite of the splendour of an unclouded sun.

"One of these fiery spouts was perpendicular, while the other somewhat oblique seemed at intervals to diminish or increase. Rocks not yet melted, in sharp fragments, distinguishable on the purple of the burning waves by their deep black hue, were pushed with violence from amidst the melted matter in which they had passed from the cavities of the mountain, and fell with great noise, describing a long parabola. A continual noise, resembling that of a vast cataract, accompanied this majestic scene, which filled the soul at once with terror and admiration."

The account of several eruptions of this grand volcano is also interesting. The lava sometimes give indications of containing mineral alkali. In the eruption of 1800, the lava fell in three torrents into a ravine, about eighty feet in depth, forming a horrible cascade, the middle, or hottest torrent being, by the account communicated to M. Bory, as fluid as water, while the two others seemed to have the consistence of honey. When the lava joined

the sea, the scene was tremendous, but there is no hint of any appearance of basaltic columns. The spouts of fire often produce the phenomenon of cords of lava, twisted in different directions.

[Phil. Trans. Cook. De Borda. Glas. Bory.]

CHAP. XV.

AMERICAN VOLCANOES.

W

SECTION I.

Volcanoes of Mexico:

E shall now proceed to a brief notice of the chief volcanoes of the American continent, and shall commence with the northern side of the isthmus.

The very singular territory of Mexico, or New Spain, contains numerous volcanoes of a powerful and extraordinary character. Not fewer than twenty-one are laid down on the maps, from that of Soconusco, in the north, to that of Vara in the south. They are all in the south western coast; and after a considerable interval, reemerge towards the eastern coast in the vicinity of the city of Mexico. The principal are those of Orizava, Popacatepec, Iztaccihuath, Ilascala, Tentzon, Toloccam, and above all Jorullo, or Xurullo.

The volcano of Orizaba, or as Clavigero writes it, Pojauhtecatl, began to send forth smoke in 1545, and continued its emissions for twenty years, when it ceased, and has not since renewed them. This celebrated mountain lies sixty miles to the south-east of the city of Mexico, not far from the road to Vera Cruz. According to D'Auteroche, it is the loftiest in the Spanish territory; and according to Gage, as high as the highest of the Alps. Its summit is visible from the capital, and is covered with perpetual snow, yet its sides are adorned with forests of large cedars, pines, and other valuable and picturesque trees.

The detached mountains, called by the Mexicans Popacatapec and Iztaccihuatl, but by the Spaniards Sierra Nevada [the Snowy ridge] in the neighbourhood of each other, lie also to the south-east of Mexico, at about thirty miles distant. The crater of the former,

Clavigero makes more than half a mile wide; but though active formerly, it has not emitted flames of late. In the last centuryś however, it still continued to emit flames and ashes, the last of which overspread the country to a considerable extent. Iztaccihuath appears to have been exhausted for a longer period than the preceding. Both these mountains, like Orizava, have their summits covered with perpetual snow, in such quantities as to supply the metropolis and the adjacent country for forty miles round, as an article of luxury to the wealthy.

All the others we have enumerated have been quiescent, perhaps immemorially, except Jorullo, which is the most singular of the whole; and whose history, therefore, we shall give more at large from the very interesting account of it, lately published by M. Humboldt.

as

"The grand catastrophe," says he, " in which this volcanic mountain issued from the earth, and by which the face of a considerable extent of ground was totally altered, was perhaps one of the most extensive physical changes, that the history of our globe exhibits. Geology points out spots in the ocean, where, within the last two years, volcanic islets have arisen above the surface of the sea, near the Azores, in the Archipelago, and on the south of Iceland: but it records no instance of a mountain of scoriæ and ashes, 517 met. [563 yards] above the old level of the neighbouring plains, suddenly formed in the centre of a thousand small burning cones, thirtysix leagues from the shore, and forty-two leagues from any other volcano. This phænomenon remained unknown to the mineralogists and natural philosophers of Europe, though it took place but fifty years ago, and within six days journey of the capital of Mexico.

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Decending from the central flat towards the coasts of the Pacific ocean, a vast plain extends from the hills of Aguasarco to the villages of Toipa, and Patatlan, equally celebrated for their fine cotton plantations. Between the picachos del Mortero and the cerras de las Cuevas and de Cuiche, this plain is only from 750 to 800 met. [820 to 880 yards] above the level of the sea. Basaltic hills rise in the midst of a country, in which porphyry with base of green-stone predominates. Their summits are crowned with oaks always in ver dure, and the foliage of laurels and olives intermingled with dwarf fan palms. This beautiful vegetation forms a singular contrast with the arid plain, which has been laid waste by volcanic fire.