TRUE VOLCANOES. 287 



their average depth and the distance of their upper origin 

 from the margin of the crater or from an unopened summit. 

 The Gunung Sumbing (11,029 feet) is one of those volcanoes 

 which exhibit the finest and most regularly formed 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 de- 

 clivity decreases. Above the zone of 9000 feet there are, on 

 Gunung Sumbing, only about ten such ribs ; at an elevation 

 of 8500 feet there are thirty-two ; at 5500 feet, seventy-two ; 

 and at 3000 feet, more than ninety-five. The angle of in- 

 clination, at the same time, diminishes from 37° to 25° and 

 10^°. The ribs are almost equally regular on the volcano 

 Gunung Tengger (8702 feet), while on the Gunung Kinggit 

 they have been disturbed and coveredj 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." 



It is certain that the mass of meteoric water in this tropic- 

 al region is three or four times greater than in the temperate 

 zone ; indeed, the showers are often like water-spouts, for al- 

 though, on the whole, the moisture diminishes with the eleva- 

 tion 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 (JBarrancos) in the volcanoes of the Canary Islands, 

 and in the Cordilleras of South America, which have become 

 of importance to the traveler from the frequent descriptions 

 given by Leopold von BuchJ 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 analo- 

 gous 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 is probably 



* Junghuhn, bd. ii., s. 241-246. 



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



X Leopold von Buch, Phys. Beschr. der CanariscJten Jnscln, s. 206, 

 218, 248, and 289. 



§ Barranco and Barranca, both of the same meaning, and sufficient- 

 ly in use in Spanish America, certainly indicate properly a water-fur' 

 row or water-cleft : la quiebra que hacen en la tierra las corrientes de 

 las aguas — " una torrente que hace barrancas ;" but they also indicate 



