Note 23 — Chapter I

To the above general observations, which are made on the authority of Dr. Horsfield, it may not be uninteresting to subjoin a more particular account of two or three of the volcanos which have been examined by that gentleman; those of Tánkuban-Prahu, Papandáyang, and Gúntur are, therefore, extracted from a paper published by Dr. Horsfield in the Batavian Transactions.

"Tankuban-Prahu.​—This mountain (which has derived its name from its appearance at a distance, resembling a prahu, or boat, turned upside down) forms a vast truncated cone. Its base extends to a very great distance, and it belongs to the largest mountains of the island, forming one of its most interesting volcanos. Although it has had no violent eruption for many ages, as is evident from the progress of vegetation, and from the depth of black mould which covers its sides, its interior has continued in a state of uninterrupted activity.

"The crater is one of the largest, perhaps the largest, of the island. It has, in general, the shape of a funnel; but its sides are very irregular. The brim, or margin, which bounds it at the top, has also different degrees of elevation, rising and descending along the whole course of its circumference. The perpendicular depth at the side, where I descended (in the south), is at least two hundred and fifty feet: in the west the margin rises considerably higher. The regular circumference of the crater I estimate one English mile and nearly an half. The south side of the interior crater, near the top, is very steep. I found it impossible to descend, without the assistance of ropes tied to the shrubs at the margin. It consists here of small fragments of lava. About one-third of its depth it becomes more oblique or inclining, and the lower part consists of large piles of rocks, through which the descending streams of water have excavated a winding channel. The east side descends gradually about one-half of the depth, where it is terminated abruptly by a perpendicular pile of large rocks, which continues to the bottom. The north side is more gradually shelving than the others, and is partly covered with vegetation. The west side is one perpendicular pile of rocks. The nucleus of the mountain consists of large masses of basaltes, in which the volcanic opening is situated; and the sides exhibit piles and strata of this stone in every possible variety of configuration. In some places the rocks have the appearance of a regular wall, which is suddenly diversified by large fragments suspended apparently by a small base, and threatening to fall down every instant. Sometimes they rise in an oblique manner, and appear to have been disposed by art. But I shall not attempt a minute description of the disposition of the rocks and the strata which form the internal walls of the crater, which, without an accurate drawing, would be tedious and scarcely intelligible. The surface of the rocks which line the interior of the crater is completely calcined, generally of a white colour, sometimes inclining to grey or yellow. In many places small fragments of lava adhere to and cover the rocks of basalt: these are of different sizes, and of great variety of form and colour; but the most are calcined or burnt, or the surface like the rocks themselves. The different sides of the internal crater are excavated in many places, by furrows made by the descending water, which penetrate to a considerable depth, and expose more completely the interior basaltic composition. The bottom of the crater has a diameter of three hundred yards, but is not completely regular; its form depends on the gradual meeting of the sides below. Its surface is much diversified: it is strewed, like the sides, with immense blocks of basalt, the interstices between which are excavated, in a similar manner, by the streams of the descending water.

"Near the centre, somewhat inclining to the west side, it contains an irregular oval lake, or collection of water, whose greatest diameter is nearly one hundred yards: it dilates into several branches. The water is white, and exhibits truly the appearance of a lake of milk, boiling with a perpetual discharge of large bubbles, which rise with greatest force from the eastern side. The heat is 112° of Fahrenheit's scale: the apparent boiling arises from a constant development of fixed air. The water has a sulphureous odour; its taste is astringent, somewhat saline. Shaken in a bottle it explodes its fixed air with great violence. The sides of the lake, to some distance, are lined by a white aluminous earth, most impalpably fine, and very loose, on which account it is very difficult to approach the water. In attempting to examine its temperature, and to collect for analysis, I sunk into the earth to a considerable distance, and found it necessary to dispose large fragments of basaltes before I was able to pass over it. This earth consists of the clay (alumine) of the lavas dissolved by the sulphureous steams on the bottom of the crater; it is of the purest kind, and divided to a degree minute almost beyond conception. Large quantities have been several times thrown out of the ancient craters of the island. One eruption of this substance occurred in the year 1761 from the mountain Gedé: it was considered as an eruption of ashes.

"I was witness to a similar eruption, which occurred from the mountain of Klut, in the month of June last year. The earth very much resembled ashes, and was so impalpably fine and light, that the common breeze of the monsoon carried it from this mountain, situated in the longitude of Surabáya, to Batavia and farther westward. It possessed the properties of the purest clay, and being mixed with water became viscid and ductile. It can easily be formed into vessels, and if procurable in large quantities, might usefully be employed in the arts. All its properties indicated sufficiently that it was the alumine of the lavas, divided in an extreme degree by the causes above-mentioned. The Javanese are not wholly unacquainted with the properties of this earth. It is a custom amongst silversmiths to collect the ashes thrown out by similar eruptions, for the purpose of making moulds for the finest works.

"Towards the eastern extremity of the lake are the remaining outlets of the subterraneous fires: they consist of several apertures, from which an uninterrupted discharge of sulphureous vapours takes place. Two of these are larger than the rest; they are several feet distant from each other. The apertures are of an irregular oblong form, and covered with crystals of impure sulphur, which form from the discharged vapours, and adhere to those incrustations of the aluminous earth which have formed themselves in a great variety of configurations (hollows, tubes, &c.) near the apertures. The vapours rush out with incredible force, with violent subterraneous noises, resembling the boiling of an immense cauldron in the bowels of the mountain: their colour is white, like the concentrated vapours of boiling water. The apertures cannot be approached without the greatest danger, as their true extent cannot be discovered: they are surrounded by incrustations of sulphur adhering to delicate laminæ of the aluminous earth, which are extremely brittle. The greatest diameter of the large opening is nearly twelve inches.

"To give an adequate description of the interior of this crater would furnish matter for an able pen: the force of the impression is increased, perhaps, by the recollection of the danger which has been overcome in descending to the bottom. Every thing here contributes to fill the mind with the most awful satisfaction. It doubtless is one of the most grand and terrific scenes which nature affords; and, in the present instance, the extent of the crater, as well as the remains of the former explosions, afforded a view and enjoyment which is not in my power to describe.

"Papandayang.​—The Papandáyang, situated on the western part of the district of Cheribon, in the province of Suka-pura, was formerly one of the largest volcanos of the island; but the greatest part of it was swallowed up in the earth, after a short but very severe combustion, in the year 1772. The account which has remained of this event asserts, that near midnight, between the 11th and 12th of August, there was observed about the mountain an uncommonly luminous cloud, by which it appeared to be completely enveloped. The inhabitants, as well about the foot as on the declivities of the mountain, alarmed by this appearance, betook themselves to flight; but before they could all save themselves, the mountain began to give way, and the greatest part of it actually fell in and disappeared in the earth. At the same time, a tremendous noise was heard, resembling the discharge of the heaviest cannon. Immense quantities of volcanic substances, which were thrown out at the same time and spread in every direction, propagated the effects of the explosion through the space of many miles.

"It is estimated, that an extent of ground, of the mountain itself and its immediate environs, fifteen miles long and full six broad, was by this commotion swallowed up in the bowels of the earth. Several persons, sent to examine the condition of the neighbourhood, made report, that they found it impossible to approach the mountain, on account of the heat of the substances which covered its circumference, and which were piled on each other to the height of three feet; although this was the 24th of September, and thus full six weeks after the catastrophe. It is also mentioned, that forty villages, partly swallowed up by the ground and partly covered by the substances thrown out, were destroyed on this occasion, and that 2,957 of the inhabitants perished. A proportionate number of cattle was also destroyed, and most of the plantations of cotton, indigo, and coffee, in the adjacent districts, were buried under the volcanic matter. The effects of this explosion are still very apparent on the remains of this volcano; but I defer an account of it, till I have had an opportunity of making a more minute examination.

"Guntur.​—The whole of the eastern part of this mountain is completely naked, and exposes to view, in a striking manner, the course of the lavas of the latter eruptions: the top is a regular cone, and covered with loose fragments of lava. I shall give a very concise abstract of the observations on the mountain, and on the different streams of lava which have lately flowed from its crater. I could distinctly trace, from the base of the conical top to the roots of the mountain, five different eruptions. The latest stream of lava which I examined (the mountain has since had a later eruption) was thrown out in 1800. Its course along the top cannot be distinctly observed, being completely covered with sand and small fragments of lava, which generally rise towards the end of an eruption. At the place where the stream first appeared distinctly, it was about five yards broad and completely even on the surface: having proceeded about twenty yards further it gradually widened, and was formed into a connected stream, higher in the middle, the sides tapering or inclining towards the top, forming a ridge with a pointed or sharp back. As the stream arrived at the foot of the mountain, it spread more and more, and pursued its course to the eastward, about six hundred yards over the adjacent country. Its greatest breadth, from north to south, is about one hundred and sixty yards, and it terminates abruptly by a rounded margin, consisting of large blocks of lava piled upon each other, nearly perpendicularly, to the height of fifteen to twenty feet.

"This stream of lava, like all the others of later date which I have examined on the island, does not consist of a connected mass of fluid lava, united like a stream of melted metal; at least on the surface where it is exposed to view. It is made up of separate masses, which have an irregular (generally oblong or cubical) shape, and lie upon each other as 'loose disjointed clods,' in an immense variety of disposition. In some of these fragments I think I could observe a tendency to assume the regular basaltic figure. During its course down the steeps of the mountain, the stream, as has been observed, forms the long connected ridge (which has been described above, in the account of the volcanos, as generally covering the sides); but having arrived at the foot and spread more at large, these lumps of lava dispose themselves, in some instances, in plains, bounded by deep vallies: now they rise to a considerable height, and form a steep perpendicular eminence; then again they are piled upon each other more gradually, and appear rising by steps and divisions. But to give an accurate description of the arrangement of these fragments of lava would be unnecessarily prolix, and would require, to be clearly understood, a good drawing. In different places, the sulphureous vapours have forced their way through the interstices of the blocks of lava. The sides of their outlets (whose form is very irregular) is covered with a white calcareous crust; and the heat is so great, that small pieces of paper thrown into them are immediately singed.

"This stream of lava is bounded on the north by another, of the same nature and disposition, thrown out of the mountain (according to an estimate made from the commencement and progress of vegetation upon it) about thirty years ago. In its course along the sides of the mountain it forms the same pointed ridges above described. It affords a plain demonstration of the manner in which the surface of lava is decomposed and rendered fit for vegetation. A third district of lava bounds the new stream first described in the south: it is more extensive than the others, and consists of several distinct regions, probably thrown out during one eruption (which appears to have been more violent than the others), but in successive periods shortly following each other. It extends farther to the eastward than the others, and covers a great portion of the foot of the mountain. Vegetation has already made considerable progress upon it: in the vallies between the separate streams of lava are found not only plants but also small shrubs. At one place, near the termination of this stream, the lava is piled up in two irregular ridges to the height of twenty feet; and at a small distance from its eastern extremity, in a spot which has escaped the effects of the later eruptions, and is covered by pleasant wood, are three different hot wells, within the circumference of a quarter of a mile. In the south, this district of lava is bounded by a recent stream, which appears to have been thrown out in 1800, by the same eruption which produced the first mentioned stream. It differs from the others only in the colour of its lava, which has a reddish hue: it is less considerable in extent than any of the others, and cannot be traced far from the foot of the mountain. The fifth stream of lava which I examined is still farther towards the south, and is one of the oldest which have been discharged from the eastern part of the crater. Near the foot of the mountain, vegetation has made greater progress than in any of the other districts of lava.

"The colour of the recent lava of this mountain is jet-black or grey: one of the streams only has a reddish colour. Its texture is very loose, and its fracture very porous. The smaller fragments have much the appearance of the scoriæ of a blacksmith's forge: on being thrown against each other, they emit a sound like two bricks coming into contact. The interior crater of this mountain, as it has remained after the eruption of 1800, is less interesting than the others which I have examined. Its shape is somewhat oval, the greatest diameter being about one hundred yards: its depth is not very considerable. Its structure, in general, is similar to that of Tankuban-prahu. It has one remaining aperture, which discharges with great force hot sulphureous vapours."

Batavian Transactions, vol. ix.