composée de gros blocs semblables à du basalte, vint non seulement remplir et combler cette baie dont la profondeur etait 60 brasses mais elle forma même, au dessus de la mer, des collines très élevées et fort étendues, qui entourent le pied du volcan, et s'appuient contre les flancs de cette montagne.

Aucune des matieres qui composent cette masse soulevée, n'a été fondue ou coulante; tous les blocs étaient crevassés, et degageaient d'abondantes vapeurs, mais ce soulèvement n'a rejeté ni rapilles, ni cendres, ni pierre-ponces. Les habitants de Banda, dont les maisons se trouvent sur le revers opposé, ne s'aperçurent de ce phénomène remarquable, qu'après que la plus grande partie de ce soulèvement se fut effectué, et lorsqu'ils en eurent été avertis par les vapeurs et par l'echauffement des eaux de la mer. Lorsque M. Reinwardts visita et examina cette localitè en 1821, des vapeurs d'eau et de souffre se degageaient encore entre ces blocs entassés. Le môle élevé au milieu de la baie, est formé de couches très épaisses, qui sont inclinés des deux cotés, et dont le milieu au cime est recourbée en dôme. Les couches inferieures sont tout-a-fait compactés; les couches superieures, au contraire, sont poreuses (Boon-mesch, p. 88). Il semble que ce soit la répétition des effects du soulèvement

resembling basalt, that not only filled up this bay, whose depth was sixty fathoms, but also formed above the level of the sea very high and extensive hills, which surround the base of the volcano, and rest against the sides of this mountain.

None of the substances composing this elevated mass were in a fluid state. All the blocks contained fissures and disengaged vapors in abundance; but the eruption threw out neither rapils, cinders, nor pumice-stones. The inhabitants of Banda, whose dwellings are situated on the opposite side, did not perceive this phenomenon until the greater part of the eruption had been completed, when they became apprised of it by the vapors and the warmth of the sea-water. When Mr. Rein

wardts visited and examined the locality, in 1821, steam and sulphurous vapors were still thrown off from the coacervated blocks. The mole raised in the middle of the bay is formed of very thick strata, sloping down to either shore and rounded at the summit in the form of a dome. The lower strata are extremely compact, while the upper ones on the contrary are porous. This appears to be a further effect of the raising of the cone itself of a volcano; from which occurrence one may

du cône même d'un volcan, et par cet évenément on peut se faire une idée de la possibilité de l'elévation des grandes masses solides qui ont produit les obélisques d' Auvergne, et les murs basaltiques saillants qui terminent les filons de basalte.

IV. Extract from a Paper on "the Pitch Lake of the Island of Trinidad," by N. Nugent, M. D., Transactions of the Royal Geological Society, London, 1811, vol. 1, p. 63.

Being desirous to visit the celebrated Lake of Pitch, previously to my departure from the Island of Trinidad, I embarked with that intention in the month of October, 1807, in a small vessel at Port Spain. After a pleasant sail of about thirty miles down the Gulf of Paria, we arrived at the point la Braye, so called by the French from its characteristic feature. It is a considerable headland, about eighty feet above the level of the sea, and perhaps two miles long and two broad. We landed on the southern side of the point, at the plantation of Mr. Vessigny. We ascended the hill, which was entirely composed of porcelain-jasper rock, to the plantation, where we procured a negro guide, who conducted us through a wood about three quarters of a mile. We now perceived a strong sulphurous and pitchy smell, like that of burning coal, and soon after had a view of the lake, which at first sight appeared to be an expanse of still water, frequently interrupted by clumps of dwarf trees or islets of rushes and shrubs; but on a nearer approach we found it to be in reality an extensive plain of mineral pitch, with frequent crevices and chasms filled with water. The singularity of the scene was altogether so great, that it was some time before 1 could recover from my surprise so as to investigate it minutely. The surface of the lake is of the color of ashes, and at this season was not polished or smooth so as to be slippery; the hardness or consistence was such as to bear any weight, and it was not adhesive, though it partially received the impression of the foot; it bore us

form an idea of the possibility of the elevation of the great solid masses that have produced the obelisks of Auvergne and of the projecting walls of basalt terminating the veins of that

substance.

without any tremulous motion whatever, and several head of cattle were browsing on it in perfect security. In the dry season, however, the surface is much more yielding, and must be in a state approaching to fluidity, as is shown by pieces of recent wood and other substances being enveloped in it. Even large branches of trees which were a foot above the level, had in some way become enveloped in the bituminous matter. The interstices or chasms are very numerous, ramifying and joining in every direction; and in the wet season being filled with water, present the only obstacle to walking over the surface; these cavities are generally deep in proportion to their width, some being only a few inches in depth, others several feet, and many almost unfathomable; the water in them is good and uncontaminated by the pitch; the people of the neighborhood derive their supply from this source, and refresh themselves by bathing in it; fish are caught in it, and particularly a very good species of mullet. The arrangement of the chasms is very singular; the sides, which of course are formed of the pitch, are invariably shelving from the surface, so as nearly to meet at the bottom, but then they bulge out towards each other with a considerable degree of convexity. This may be supposed to arise from the tendency in the pitch slowly to coalesce, whenever softened by the intensity of the sun's rays. These crevices are known occasionally to close up entirely, and we saw many marks or seams from this cause. How these crevices originate it may not be so easy to explain. One of our party suggested that the whole mass of pitch might be supported by the water which made its way through accidental rents, but in the solid state it is of greater specific gravity than water, for several bits thrown into one of the pools immediately sunk.* The lake (I call it so, because I think the common name appropriate enough) contains many islets covered with long grass and shrubs, which are the haunts of birds of the most exquisite plumage,

* Pieces of asphaltum are, I believe, frequently found floating on the Dead Sea in Palestine, but this arises probably from the extraordinary specific gravity of the waters of that lake, which Dr. Marcet found to be 1.211. Mr. Hatchell states the specific gravity of ordinary asphaltum to vary from 1.023 to 1.165; but in the two varieties of that of Trinidad, it was as great as 1.336 and 1.744.

SECOND SERIES, VOL. III. NO. I.

4

as the pools are of snipe and plover. Alligators are also said to abound here, but it was not our lot to encounter any of these animals. It is not easy to state precisely the extent of this great collection of pitch; the line between it and the neighboring soil is not always well defined, and indeed it appears to form the substratum of the surrounding tract of land. We may say, however, that it is bounded on the north and west sides by the sea, on the south by the rocky eminence of porcelain jasper, before mentioned, and on the east by the usual argillaceous soil of the country; the main body may perhaps be estimated at three miles in circumference; the depth cannot be ascertained, and no subjacent rock or soil can be discovered. Where the bitumen is slightly covered by soil, there are plantations of cassava, plantains and pine-apples, the last of which grow with luxuriance, and attain to great perfection. There are three or four French and one English sugar estate in the immediate neighborhood; our opinions of the soil did not, however, coincide with that of Mr. Anderson, who, in the account he gave some years ago, thought it very fertile. It is worthy of remark, that the main body of the pitch which may properly be called the lake, is situated higher than the adjoining land, and that you descend by a gentle slope to the sea, where the pitch is much contaminated by the sand of the beach. During the dry season, as I have before remarked, this pitch is much softened, so that different bodies have been known slowly to sink into it; if a quantity be cut out, the cavity left will be shortly filled up; and I have heard it related, that when the Spaniards undertook formerly to prepare the pitch for economical purposes, and had imprudently erected their cauldrons on the very lake, they completely sunk in the course of a night, so as to defeat their intentions. Numberless proofs are given of its being at times in this softened state: the negro houses of the vicinage, for instance, built by driving posts in the earth, frequently are twisted or sunk on one side. In many places it seems to have actually overflown like lava, and presents the wrinkled appearance which a sluggish substance would exhibit in motion.

This substance is generally thought to be the asphaltum of naturalists in different spots however it presents different appearances. In some parts it is black, with a splintery conchoidal fracture, of considerable specific gravity, with

little or no lustre, resembling particular kinds of coal, and so hard as to require a severe blow of the hammer to detach or break it; in other parts, it is so much softer, as to allow one to cut out a piece in any form with a spade or hatchet, and in the interior is vesicular and oily; this is the character of by far the greater portion of the whole mass; in one place it bubbles up in a perfectly fluid state, so that you may take it up in a cup, and I am informed that in one of the neighboring plantations there is a spot where it is of a bright color, shining, transparent, and brittle, like bottle-glass or resin. The odor in all these instances is strong, and like that of a combination of pitch and sulphur. No sulphur however is any where to be perceived, but from the strong exhalation of that substance and the affinity which is known to exist between the fluid bitumen and it, much is, no doubt, contained in a state of combination; a bit of the pitch held in the candle melts like sealing-wax, and burns with a light flame which is extinguished whenever it is removed; and on cooling the bitumen hardens again. From this property it is sufficiently evident that this substance may be converted to many useful purposes; and accordingly it is universally used in the country wherever pitch is required.

I have been informed by several persons that the sea in the neighborhood of La Braye is occasionally covered with a fluid bitumen, and in the south-eastern part of the island there is certainly a similar collection of this bitumen, though of less extent, and many small detached spots of it are to be met with in the woods; it is even said that an evident line of communication may thus be traced between the two great receptacles. There is every probability, that in all these cases the pitch was originally fluid, and has since become inspissated by exposure to the air, as happens in the Dead Sea and other parts of the east.