5399, so that it must have lost 190 yards; and indeed the people in the vicinity say, that they have seen its summit crumble away before their eyes.

During our stay at Riobancha, we accidentally made a very curious discovery. The state of the province of Quito, previous to its conquest by the Inca Tupaynpangi, in 1470, is wholly unknown: but the king of the Indians, Leandro Zapla, who resides at Lican, and has a mind extraordinarily cultivated for an Indian, possesses manuscripts composed by one of his ancestors, in the sixteenth century, which contains the history of that period. They are written in the Paraguay tongue, which was formerly general in Quito, but is now lost, having been supplanted by the Inca. Fortunately another of Zapla's ancestors amused himself by translating these memoirs into Spanish. We have obtained from them valuable information, particularly in the memorable period of the eruption of Nevado del Atlas, which must have been the highest mountain in the world, loftier than Chimboraco, and ealled by the Indians Capa-urca, or chief of mountains.

[Bouguer. Estalla. Humboldt.]

SECTION III.

Volcanic Phænomena in the West Indies.

ALTHOUGH active volcanoes are by no means common in the islands distinguished by the name of the West Indies, there are few of them that do not betray some traces either of a volcanic origin or of volcanic effects. The Caribees are particularly characterised by such features, and especially Martinique, Guadaloupe, and St. Lucia. The mountain-soil of the first of these consists, to a very considerable extent, of pumice, either in lumps or powder, occasionally intermixed with a ferruginous sand, which is not unfre quently a volcanic production.

On the island of St. Lucie, or St. Lucia, are some bigh and craggy mountains, which bear evident marks of volcanoes; in one deep valley there are several ponds, the water of which boils up in a very powerful manner, and the streams that issue from it retain their heat at the distance of three miles from their source.

The mountains of Guadaloupe are, according to De Borda, not less lofty than those of Martinique, and the Souffriere or Sulphur

Mountain, ejected both smoke and flames during the time of his visit to the island. This very singular mountain is the highest of the whole; its summit is perfectly bare, nothing growing upon it but ferns, mosses, and a few other cryptogamic plants: but it affords a fine view of the neighbouring islands of Dominica, Mariegalante, Martinico, Montserrat, Nevis, and various others. Upon the highest part is a rugged platform, covered with burnt stones of all sizes; and from several clefts and chinks issue smoke. On the east side are two mouths, which open into a pit of sulphur, one of which is an oval hole of about an hundred feet in its greatest diameter, out of which also frequently arise thick clouds of black smoke, accompanied with sparks of fire. The negroes who sell brunstone fetch it from this mountain. About two hundred paces below the lowest of these mouths are three pools of very hot water, four or five paces from each other: the water of the largest is very dark coloured, and smells like that of a smith's forge; the second is whitish, and has the taste of alum; the third is blue, and has a vitriolic taste. Here are also several springs, which, uniting their streams, form various torrents. The middle and bottom of this burning mountain are extremely different from the top of it, being covered with tall trees and herbage, watered by a number of rivulets, and cultivated with the utmost care and industry.

Almost every island in the western Archipelago, particularly those which bave the highest laud, has, in like manuer, its Sulphur-hill, or Souffrière, as it is denominated by the French. In some of these the volcano has become extinct, and is no longer to be traced; but in others, as Guadaloupe, St. Lucia, and St. Vincent, there are decided and well-characterised craters, which are occasionally active, and throw out ashes, scoriæ, and lava with the flame.

The most singular of these Souffrières occurs in the island of Montserrat, and is thus ably described by Dr. Nugent. "The island of Montserrat, so called by the Spaniards from a fancied resemblance to the celebrated mountain of Catalonia, is every where extremely rugged and mountainous, and the only roads, except in one direction, are narrow bridle-paths winding through the recesses of the mountains; there is hardly a possibility of using wheeled carriages, and the produce of the estates is brought to the place of shipment on the backs of mules. Accompanied by a friend, I accordingly set out on horseback from the town of Plymouth, which

is situated at the foot of the mountains on the sea shore. We proceeded by a circuitous and steep route about six iniles, gradually ascending the mountain, which consisted entirely of an uniform porphyritic rock, broken every where into fragments and large blocks, and which in many places was so denuded of soil as to render it a matter of astonishment how vegetation, and particularly that of the cane, should thrive so well. The far greater part of the whole island is made up of this porphyry, which by some systematics would be considered as referable to the newest floëtz trap formation, and by others would be regarded only as a variety of lava. It is a compact and highly-indurated argillaceous rock of a grey colour, replete with large and perfect crystals of white felspar and black hornblende. Rocks of this description generally pass in the West Indies by the vague denomination of fire-stone, from the useful property they possess of resisting the operation of intense heat. A considerable quantity of this stone is accordingly exported from Montserrat to the other islands which do not contain it, being essential in forming the masonry around the copper boilers in sugar works. We continued our ride a considerable distance beyond the estate called Galloway's (where we procured a guide) till we came to the side of a very deep ravine which extends in a winding direc tion the whole way from one of the higher mountains to the sea. A rugged horse-path was traced along the brink of the ravine, which we followed amidst the most beautiful and romantic scenery. At the head of this ravine is a small amphitheatre formed by lofty surrounding mountains, and here is situated what is termed "The Sulphur." Though the scene was extremely grand and well worthy of observation, yet I confess I could not help feeling a good deal disappointed, as there was nothing like a crater to be seen, or any thing else that could lead me to suppose the place had any connexion with a volcano. On the north, east, and west sides were lofty mountains wooded to the tops, composed apparently of the same kind of porphyry we had noticed all along the way. On the south, the same kind of rock of no great height, quite bare of vegetation, and in a very peculiar state of decomposition. And on the southeastern side, our path and the outlet into the ravine. The whole area thus included, might be three or four hundred yards in length, and half that distance in breadth. The surface of the ground, not occupied by the ravine, was broken and strewed with fragments and

and masses of the porphyritic rock, for the most part so exceedingly decomposed as to be friable and to crumble on the smallest pressure. For some time I thought that this substance, which is perfectly white, and in some instances exhibits an arrangement like crystals, was a peculiar mineral; but afterwards became convinced, that it was merely the porphyritic rock singularly altered, not by the action of the air or weather, but, as I conjecture, by a strong sulphureous or sulphuric acid vapour which is generated here, aud which is probably driven more against one side by the eddy wind up the ravine, the breeze from any other quarter being shut out by the surrounding hills*.

Amidst the loose stones and fragments of decomposed rock are many fissures and crevices, whence very strong sulphureous exhalations arise, and which are diffused to a considerable distance; these exhalations are so powerful as to impede respiration, and near any of the fissures are quite intolerable and suffocating. The buttons of my coat, and some silver and keys in my pockets, were instantaneously discoloured. An intense degree of heat is at the same time evolved, which, added to the apprehension of the ground crumbling and giving way, renders it difficult and painful to walk near any of these fissures. The water of a rivulet which flows down the sides of the mountain and passes over this place, is made to boil with vio. lence, and becomes loaded with sulphureous impregnations. Other

* This peculiar decomposition of the surrounding rock has been frequently observed in similar situations, and under analogous circumstances, and has I find been accounted for by other persons in tho same way: thus Dolomieu says, “La couleur blanche des pierres de l'interieur de tous les craters inflammés est due à une veritable alteration de la lave produite par les vapeurs acido-sulfureuses qui les penetrent, et qui se combinent avec l'argile qui leur sert de base, y formant l'alun que l'on retire des matières volcaniques.” Voy. aux Isles de Lipari, p. 18.

And he afterwards adds, "Cette alteration des laves par les vapeurs acidosulfureuses, est une espèce d'analyse que la nature fait elle même des matières volcaniques. Il y a des laves sur lesquelles les vapeures n'ont pas encore eu assez de tems d'agir pour les dénaturer entièrement, et alors on les voit dan différens etats de decomposition que l'on reconnoit par le couleur."

Alum is doubtless formed at this place, as well as elsewhere, under similar circumstances: the potash necessary for the composition of this salt, being, as well as the argil, derived from the surrounding rock.

branches of the same rivulet which do not pass immediately near these fissures, remain cool and limpid; and thus you may with one hand touch one rill that is at the boiling point, and with the other hand touch another rill which is of the usual temperature of water in that climate. The exhalations of sulphur do not at all times proceed from the same fissures, but new ones appear to be daily formed, others becoming, as it were, extinct. On the margins of these fissures, and indeed almost over the whole place, are to be seen most beautiful crystallizations of sulphur, in many spots quite as fine and perfect as those from Vesuvius, or indeed as any other specimens I have ever met with. The whole mass of decomposed rock in the vicinity is, in like manner, quite penetrated by sulphur. The specimens which I collected of the crystallized sulphur, as well as of the decomposed and undecomposed porphyry, were left inadvertently on board the packet at Falmouth, which prevents my having the pleasure of exhibiting them to the Society. I did not perceive at this place any trace of pyrites, or any other metallic substance, except indeed two or three small fragments of clay ironstone at a little distance, but did not discover even this substance any where in situ. It is very probable that the bed of the glen or ravine might throw some light on the internal structure of the place; but it was too deep, and its banks infinitely too precipitous, for me to venture down to it. I understood that there was a similar exhalation and deposition of sulphur on the side of a mountain not more than a mile distant in a straight line; and a subterranean communication is supposed to exist between the two places.

[De Borda, Journal des Mines, Geological Transact. Vol. I.]

CHAP. XVI.

ISLANDS SUDDENLY THROWN UP FROM THE SEA.

BESIDES the convulsions of nature displayed in volcanoes, other operations are carried on below the fathomless depths of the sea, the nature of which can only be conjectured of by the effects pro