Note 24 — Chapter I

Mineral wells, of various qualities, are found in almost every part of the island. As an instance of the hot wells, the following account of those found in Cheribon is selected. "At the village of Bongas (situated about ten miles to the north-east of Karang-Sambong) I directed my route to the large mountain, in order to examine part of the hills along its foot, called the hills of Pana-wangan, and several hot wells which are found near their borders. On approaching these hills, after a very gentle acclivity covered entirely by calcareous stones, I very soon came to the spot of the hot wells. They are found on a gently inclining plain, about one hundred yards in circumference. This plain is perfectly white; and on approaching it, it is perceived at some distance by a sulphureous vapour, arising from the whole neighbourhood. The water springs from several apertures, but their temperatures are not equal; the hottest indicates the degree of one hundred and thirty of Fahrenheit's scale. They all contain a very large quantity of calcareous earth in solution and suspension, which coming into contact with the air, immediately separates, and adheres to the surrounding objects, or is precipitated to the ground. The branches of the shrubs in the vicinity are all enveloped by a stalactical incrustation. The water from the different wells gently descending the white calcareous plain, is collected in a rivulet below. A large number of calcareous rocks are found in the vicinity of the plains; some are covered with elegant crystals of calcareous spar, others have a coralline appearance, and some have the fracture of alabaster. On proceeding up the hills, immense irregular blocks of calcareous rocks are found strewed about in the valleys. About one hundred yards above this district are several wells of naphtha, or petroleum. It rises in small plashes of water, about twelve or eighteen inches in diameter, upon which it drives its black specks, emitting the peculiar odour of the petroleum. The earth in the circumference of these plashes is strongly impregnated with this oil: it is very tough, and from that immediately bounding apertures, the naphtha flows out on its being pressed; some portions exactly resemble asphaltum. A considerable space of ground is occupied by these wells. The stones are all calcareous. A few hundred yards above this spot, the borders of the hills become very steep. I examined them to some extent. They are composed exclusively of calcareous stones. Several extensive stalactitic caves are found at no great distance above the wells; they exhibit the usual appearances of calcareous caves and vaults. The process of incrustation is continually going on. In some places, deep perforations extend into the heart of the hills."​—Essay on the Mineralogy of Java, by Dr. Horsfield. Bat. Trans. vol. ix.

Among other objects of curiosity, which can only be illustrated by particular description, are the explosions of mud, situated between the district of Grobogan on the west, and of Blora and Jipang on the east. By the natives they are termed Blédeg, and are described by Dr. Horsfield as salt wells.

"These salt wells," he observes, "are dispersed through a district of country several miles in circumference, the base of which, like that of other parts of the island which furnish mineral and other saline waters, is limestone. They are of considerable number, and force themselves upwards, through apertures in the rocks, with some violence and ebullition. The waters are strongly impregnated with sea-salt, and yield upon evaporation very good salt for culinary purposes. (In quantity not less than two hundred tons in the year.)

"About the centre of this limestone district, is found an extraordinary volcanic phenomenon. On approaching it from a distance, it is first discovered by a large volume of smoke rising and disappearing at intervals of a few seconds, resembling the vapours arising from a violent surf: a dull noise is heard, like that of distant thunder. Having advanced so near, that the vision was no longer impeded by the smoke, a large hemispherical mass was observed, consisting of black earth, mixed with water, about sixteen feet in diameter, rising to the height of twenty or thirty feet in a perfectly regular manner, and as it were pushed up, by a force beneath; which suddenly exploded with a dull noise, and scattered about a volume of black mud in every direction. After an interval of two or three, or sometimes four or five seconds, the hemispherical body of mud or earth rose and exploded again. In the same manner this volcanic ebullition goes on without interruption, throwing up a globular body of mud, and dispersing it with violence through the neighbouring plain. The spot where the ebullition occurs is nearly circular and perfectly level, it is covered only with the earthy particles impregnated with salt water, which are thrown up from below; the circumference may be estimated at about half an English mile. In order to conduct the salt water to the circumference, small passages, or gutters, are made in the loose muddy earth, which lead it to the borders, where it is collected in holes dug in the ground for the purpose of evaporation.

"A strong, pungent, sulphureous smell, somewhat resembling that of earth-oil, is perceived on standing near the explosion; and the mud recently thrown up possesses a degree of heat greater than that of the surrounding atmosphere. During the rainy season these explosions are more violent, the mud is thrown up much higher, and the noise is heard at a greater distance.

"This volcanic phenomenon is situated near the centre of the large plain which interrupts the large series of volcanos; and owes its origin to the general cause of the numerous volcanic eruptions which occur on the island." Batavian Trans. vol. ix.

"These salt wells, as Dr. Horsfield terms them, and other phenomena connected with them, appear to be precisely of the same description as the mud volcano at Macalouba, in Sicily, and the eruptions described by Pallas, at Tainan and Kercha (the boundary of Europe to the south-east of Little Tartary) and no doubt owe their origin to similar causes​—the extrication of gas, as well described by Dallas, in his Translation of the History of Volcanos, by the Abbé Ordinaire," page 249. All the phenomenon described in this work, as well in Sicily as at Tainan and Kercha, are to be found in Java, where, on the hypothesis of the Abbé, "the vitriolic acid liberating a great quantity of fixed air from the salts with which this argillaceous and limy mass is impregnated, is observed escaping copiously, by a general bubbling on the surface of the plain, when the substances are sufficiently diluted by rain," &c.

On the hypothesis of the Abbé it may, therefore, be doubted whether the assertion "that the Blédegs owe their origin to the general cause of the numerous volcanos on the island, is correct." Pallas conceives that the phenomenon at Kercha and Tainan may be explained by supposing a deep coal mine to have been for ages on fire, that the sea broke in upon it, that the water was turned into steam, and that the expansion occasioned thereby, and the struggle of the different gases to get free, force the upper surface, &c. but there seems no necessity for admitting the action of fire; the mud he describes is only luke-warm, this is precisely the case in Java.

It is remarkable that in Java, as in Sicily, in the vicinity of these phenomena, "the country around is of calcareous earth; briny springs and salt mines are found in the neighbourhood; some beds of oil of petroleum are also observed floating on adjacent stagnant waters."