93

ribs, as the mountain is bare of forest trees and clothed with grass. According to the measurements given by Junghuhn, the number of ribs increases by division in proportion as the declivity decreases. Above the zone of 9000 feet there are, on Gunung Sumbing, only about 10 such ribs; at an elevation of 8,500 feet there are 32; at 5500 feet, 72; and at 3,000 feet, more than 95. The angle of inclination at the same time diminishes from 37° to 25° and 101°. The ribs are almost equally regular on the volcano Gunung Tengger (8702 feet), whilst on the Gunung Ringgit they have been disturbed and covered by the destructive eruptions which followed the year 1586. "The production of these peculiar longitudinal ribs and the mountain fissures lying between them, of which drawings are given, is ascribed to erosion by streams."

T

It is certain that the mass of meteoric water in this tropical region is three or four times greater than in the temperate zone, indeed the showers are often like waterspouts, for although, on the whole, the moisture diminishes with the elevation of the strata of air, the great mountain cones exert on the other hand a peculiar attraction upon the clouds, and, as I have already remarked, in other places, volcanic eruptions are in their nature productive of storms. The clefts and valleys (Barrancos), in the volcanoes of the Canary Islands, and in the Cordilleras of South America, which have become of importance to the traveller from the frequent descriptions given by Leopold von Buch 5 and myself, because they open up to him the interior of the mountain, and sometimes even conduct him up to the vicinity of the highest summits, and to the circumvallation of a crater of elevation, exhibit analogous phenomena; but although these also at times carry off the accumulated meteoric waters, the original formation of the barrancos" upon the slopes of the volcanoes

93 Junghuhn, Bd. ii. s. 241–246.

Op. cit. sup. s. 566, 590 and 607-609.

95

95 Leopold von Buch, Phys. Beschr. der Canarischen Inseln, s. 206, 218, 248, and 289.

96 Barranco and Barranca, both of the same meaning, and suffi. ciently in use in Spanish America, certainly indicate properly a waterfurrow or water-cleft: la quiebra que hacen en la tierra las corrientes de las aguas ;—"una torrente que hace barrancas ;” but they also indi

is probably not to be ascribed to these. Fissures, caused by folding in the trachytic mass, which has been elevated whilst soft and only subsequently hardened, have probably preceded all actions of erosion and the impulse of water. But in those places where deep barrancos appeared in the volcanic districts visited by me on the declivities of bellshaped or conical mountains (en las faldas de los Cerros barrancosos), no trace was to be detected of the regularity, or radiate ramification with which we are made acquainted by Junghuhn's works in the singular outlines of the volcanoes of Java." The greatest analogy with the form here referred to is presented by the phenomenon to which Leopold von Buch, and the acute observer of volcanoes, Poulet Scrope, have already directed attention, namely, that great fissures almost always open at a right or obtuse angle from the centre of the mountain, radiating (although undivided), in accordance with the normal direction of the declivities, but not transversely to them.

The belief in the complete absence of lava-streams upon the island of Java,98 to which Leopold von Buch appeared to

cate any chasm. But that the word barranca is connected with barro, clay, soft, moist loam, and also road-scrapings, is doubtful.

97 Lyell, Manual of Elementary Geology, 1855, chap. xxix, p. 497. The most remarkable analogy with the phenomenon of regular ribbing in Java, is presented by the surface of the Mantle of the Somma of Vesuvius, upon the seventy folds of which, an acute and accurate observer, the astronomer Julius Schmidt, has thrown much light (Die Eruption des Vesuvs im Mai, 1855, s. 101-109). According to Leopold von Buch, these valley-furrows are not originally rain-furrows (fiumare), but consequences of cracking (folding, étoilement) during the first upheaval of the volcano. The usually radial position of the lateral eruptions in relation to the axis of the volcano, also appears to be connected therewith (s. 129).

98 "Obsidian, and consequently pumice-stones, are as rare in Java. as trachyte itself. Another very curious fact is the absence of any stream of lava in that volcanic island. M. Reinwardt, who has himself observed a great number of eruptions, says expressly that there have never been instances of the most violent and destructive eruption having been accompanied by lavas."-Léopold de Buch, Descr. des Iles Canaries, p. 419. Amongst the volcanic rocks of Java, for which the Cabinet of Minerals at Berlin is indebted to Dr. Junghuhn, dioritic-trachytes are most distinctly recognizable at Burungagung, s. 255 of the Leidner catalogue, at Tjinas, s. 232, and in the Gunung Parang, situated in the district Batu-gangi. This is conseVOL. V.

X

incline in consequence of the observations of Reinwardt, has been rendered more than doubtful by recent observations. Junghuhn, indeed, remarks “that the vast volcano Gunung Merapi has not poured forth coherent, compact lava-streams within the historical period of its eruptions, but has only thrown out fragments of lava (rubbish), or incoherent blocks of stone, although for nine months, in the year 1837, fiery streams were seen at night running down the cone of eruption." But the same observant traveller has distinctly quently the identical formation of dioritic-trachyte of the volcanoes of Orizaba and Toluca in Mexico, of the island Panaria in the Lipari Islands, and of Ægina in the Ægean Sea !

99

99 Junghuhn, Bd. ii. s. 309 and 314. The fiery streaks which were seen on the volcano G. Merapi, were formed by closely approximated streams of scoriæ (traînées de fragmens), by non-coherent masses, which roll down during the eruption towards the same side, and strike against each other from their very different weights on the steep declivity. In the eruption of the G. Lamongan on the 26th March, 1847, a moving line of scoriæ of this kind divided into two branches several hundred feet below its point of origin. "The fiery streak,” we find it expressly stated (Bd. ii. s. 767), “"did not consist of true fused lava, but of fragments of lava rolling closely after one another." The G. Lamongan and the G. Semeru are the two volcanoes of the island of Java, which are found to be most similar, by their activity in long periods, to the Stromboli, which is only about 2980 feet high, as they, although so remarkably different in height (the Lamongan being 5340 and the Semeru 12,235 feet high), exhibited eruptions of scoriæ, the former after pauses of 15 to 20 minutes (eruptions of July, 1838, and March, 1817), and the second of 1 to 3 hours (eruptions of August, 1836, and September, 1844,) (Bd. ii. s. 554 and 765-769). At Stromboli itself, together with numerous eruptions of scoriæ, small, but rare effusions of lava also occur, which, when detained by obstacles, sometimes harden on the declivities of the cone. I lay great stress upon the various forms of continuity or division, under which completely or partially fused matters are thrown or poured out, whether from the same or different volcanoes. Analogous investigations, undertaken under various zones, and in accordance with guiding ideas, are greatly to be desired, from the poverty and great one-sidedness of the views, to which the four active European volcanoes lead. The question raised by me in 1802 and by my friend Boussingault in 1831,-whether the Antisana in the Cordilleras of Quito has furnished lava-streams? which we shall touch upon hereafter, may perhaps find its solution in the division of the fluid matter. The essential character of a lava-stream is that of a uniform, coherent fluid, -a band-like stream, from the surface of which scales separate during its cooling and hardening. These scales, beneath which the nearly homogeneous lava long continues to flow, upraise

2

described, in great detail, three black, basaltic lava-streams on three volcanoes :-Gunung Tengger, Gunung Idjen, and Slamat.100 On the latter the lava-stream, after giving rise to a water-fall, is continued into the tertiary rocks. From such true effusions of lava, which, form coherent masses, Junghuhn very accurately distinguishes, in the eruption of Gunung Lamongan, on the 6th July, 1838, what he calls a stonestream, consisting of glowing and usually angular fragments, erupted in a row. "The crash was heard of the breaking stones, which rolled down, like fiery points, either in a line or without any order." I purposely direct especial attention to the very various modes in which fiery masses appear on the slopes of a volcano, because in the dispute upon the maximum angle of fall of lava-streams, glowing streams of stones (masses of scoria) following each other in rows, are sometimes confounded with continuous lava-streams.

As the important problem of the rarity or complete deficiency of lava-streams in Java,- -a problem which touches on the themselves in part, obliquely or perpendicularly, by the inequality of the internal movement and the evolution of hot gases; and when, in this way, several lava-streams, flowing together, form a lava lake, as in Iceland, a field of detritus or fragments is produced on their cooling. The Spaniards, especially in Mexico, call such a district, which is very disagreeable to pass over, a malpais. Such lava-fields, which are often found in the plain at the foot of a volcano, remind one of the frozen surface of a lake, with short, upraised ice-blocks.

100 The name G. Idjen, according to Buschmann, may be explained by the Javanese word hidjên, singly, alone, separately:-a derivative from the substantive hidji or widji, grain, seed, which with sa expresses the number one. With regard to the etymology of G. Tengger, see the important work of my brother upon the connections between Java and India (Kawi-Sprache, Bd. i, s. 188), where there is a reference to the historical importance of the Tengger Mountain, which is inhabited by a small tribe of people, who, opposed to the now general Mahomedanism of the island, have retained their ancient Indo-Javanic faith. Junghuhn, who has very industriously explained the names of mountains from the Kawi language says (Th. ii. s. 554), that in the Kawi, Tengger signifies hill; the word also receives the same signification in Gericke's Javanese Dictionary (Javaansch-nederduitsch Woordenbock, Amst., 1847). Slamat, the name of the high volcano of Tegal, is the well-known Arabic word selamat, which signifies happiness and safety.

1 Junghuhn, Bd. ii. Slamat, s. 153 and 163; Idjen, s. €98; Tengger, 8. 773.

2 Bd. ii. s. 760-762.

internal constitution of volcanoes, and, which I must add, has not been treated with sufficient earnestness, has recently been so often spoken of, the present appears a fitting place in which to bring it under a more general point of view. Although it is very probable that, in a group or series of volcanoes all the members stand in a certain common relation to the general focus, the molten interior of the earth, still each individual presents peculiar physical and chemical processes as regards strength and frequency of activity, degree and form of fluidity, and material difference of products,—peculiarities which cannot be explained by the comparison of the form, and elevation above the present surface of the sea. The gigantic mountain, Sangay, is as uninterruptedly active as the lowly Stromboli; of two neighbouring volcanoes, one throws out pumice-stone without obsidian, the other both at once; one furnishes only loose cinders, the other lava flowing in narrow streams. These characteristic processes, moreover, in many volcanoes appear not to have been always the same at various epochs of their activity. To neither of the two continents is rarity or total absence of lava streams to be peculiarly ascribed. Remarkable distinctions only occur in those groups with regard to which we must confine ourselves to definite historical periods near to our own times. The non-detection of single lava-streams depends simultaneously upon many conditions. Amongst these we may instance the deposition of vast layers of tufa, rapilli, and pumice-stone; the simultaneous and non-simultaneous confluence of several streams, forming a widely exSended lava-field covered with detritus; the circumstance that in a wide plain the small conical eruptive-cones, the volcanic platform, as it were, from which, as at Lancerote, the lava had flowed forth in streams, have long since been destroyed. In the most ancient conditions of our unequally cooling planet, in the earliest foldings of its surface, it appears to me very probable that a frequent viscid outflow of trachytic and doleritic rocks, of masses of pumice-stone or perlite, containing obsidian took place from a composite network of fissures, over which no platform has ever been elevated or built up. The problem of such simple effusions from fissures deserves the attention of geologists.

In the series of Mexican volcanoes, the greatest and, since