TliUE VOLCANOES. 481 



totally different composition (containing labraclorite instead 

 of oligoclase), shows neither obsidian nor pumice ; this same 

 deficiency I observed on my ascent of the Tungurahua. The 

 volcano Purace, near Popayan, has a great deal of obsidian 

 mixed in its trachytes, but has never yielded any pumice. 

 The immense plains out of which rise the Ilinissa, Carguai- 

 razo, and Altar are covered with pumice. The subterranean 

 pumice- quarries near Lactacunga, as well as those of 

 Huichapa south-east of Queretaro; and the accumulations 

 of pumice at the Rio Mayo, 13 those near Tschegem in the 

 Caucasus, 14 and near Tollo 15 in Chili, at a distance from active 

 volcanic structures, appear to me to belong to the phenomena 

 of eruption from the numerous fissures in the level surface of 

 the earth. Another Chilian volcano, that of Antuco, 16 (of 

 which Poppig has given a description as scientifically impor- 

 tant as it is agreeably written) produces, like Vesuvius, 

 ashes, triturated rapilli (sand), but gives out no pumice, 

 no vitrified or obsidian-like mineral. Without the presence 

 of either obsidian or glassy felspar, we sometimes meet with 

 pumice in trachytes of very dissimilar composition, although 

 in many cases it is not present. Pumice, as Charles Darwin 

 observes, is entirely wanting in those of the Archipelago of 

 the Galapagos. We have already remarked in another place 

 that cones of cinders are wanting in the mighty volcano of 

 Mauna Loa in the Sandwich Islands, as well as in the vol- 

 canoes of the Eifel " which once emitted lava-streams. 

 Though the island of Java contains a series of more than 

 forty volcanoes, of which as many as twenty-three are still 

 active, yet Junghuhn was only able to discover two points 

 in the volcano of Gunung Guntur, near Bandong and the 

 great Tengger Mountains, 18 in which masses of obsidian have 

 been formed. These do not appear to have given occasion 



13 Nivellement Barometrique, in Humboldt, Observat. Astron., vol. i, 

 p. 305, No. 149. 



14 See above, p. 345. 



15 For an account of the pumice-bill of Tollo, at a distance of two 

 days' journey from tbe active volcano of Maypu, which has itself never 

 ejected a fragment of such pumice, see Meyen, Reise urn die Erde, 

 Th. i, s. 338 und 358. 



16 Poppig, Reise in Chile und Peru, Ed. i, s. 426. 



17 See above, p. 392, and notes, pp. 320 3. 



18 Franz Junghuhn, Java, Bd. ii, s. 388, 592. 



VOL. V. 2 I 



