ON ITS EXTERIOE. VOLCANOES. 445 



gimga, as well as those of Huichapa, south-east of Que- 

 retaro ; the pumice accumulations at the Rio Mayo ( G37 ) ; 

 and those near Tschegem in the Caucasus ( 638 ) ; and near 

 Tollo ( 639 ) in Chili, at a distance from any active volcanic 

 frameworks, all appear to me to belong to the class of 

 phenomena of eruptions in the variously fissured flat 

 surface of the earth. Another Chilian volcano, that of 

 Antuco( 640 ), of which Poppig has given a description 

 as scientifically important as it is pleasing in style, 

 produces, like Vesuvius, " ashes," small triturated rapilli 

 (sand), but no pumice, and no vitrified or obsidian-like 

 rock. Without the presence of obsidian or of glassy 

 felspar, and with great diversity of composition in the 

 trachytes, we see both the production and the non- 

 ' production of pumice. Pumice, as the sagacious Darwin 

 has observed, is, moreover, wanting in the entire group 

 of the Galapagos. We have already remarked elsewhere 

 that in the great volcano of the Sandwich Islands, Mauna 

 Loa, as well as in the volcanoes of the Eifel, which once 

 poured forth lava( 641 ), cones of ashes are wanting. 

 Although the island of Java has a range of more than 

 forty volcanoes, of which twenty-three are now active, 

 yet Junghuhn has only been able to discover two points 

 at the volcano Grunung Gruntur, not far from Bandong, 

 and in the great Tengger mountains ( 642 ) where masses 

 of obsidian have formed. They do not appear to have 

 occasioned any formation of pumice. The seas of sand 

 (dasar), which are at a mean height of nearly 7000 feet 

 above the sea, are covered, not with pumice, but with a 

 layer of rapilli, which are described as half-vitrified 

 obsidian-like pieces of basalt. The cone of Vesuvius, 

 which has never emitted pumice, sent forth, from the 



