456 COSMOS. 



Third Division. "The ground-mass of this dioritic tra- 

 chyte contains many small crystals of oligoclase with black 

 hornblende and brown magnesian-mica. To this belong 

 the trachytes of ^gina, 74 of the valley of Kozelnik near 

 Schemnitz 75 , of Nagyag in Transylvania, of Montabaur in 

 the Duchy of Nassau, of the Stenzelberg and the Wolken- 

 biirg in the Siabengebirge near Bonn, of the Puy de Chau- 

 mout, near Clermont in Auvergne, and of the Liorant in 

 Cantal; also the Kasbegk in the Caucasus, the Mexican vol- 

 canoes of Toluca 76 and Orizaba, the volcano of Purace and the 

 splendid columns of Pisoje 77 near Popayan, though whether 

 the latter are trachytes is very uncertain. The domites 

 of Leopold von Buch belong likewise to this third di- 

 vision. In the white, fine-grained fundamental mass of 

 the trachytes of the Puy de Dome are found glassy crys- 

 tals, which were constantly taken for felspar, but which are 

 always streaked on the most distinct cleavage surface, and 

 are oligoclase ; hornblende and some mica are also present. 

 Judging from the volcanic specimens for which the royal 



74 From the close propinquity of Cape Perdica of the island of 

 JEgma, to the long famous red-brown Trozen-trachytes (Cosmos, see 

 above, p. 229) of the peninsula of Methana, and from the sulphur- 

 springs of Bromolimni, it is probable that the trachytes of Methana, as 

 well as those of the island of Kalauria, near the small town of Poros, 

 belong to the same third division of Gustav Rose (oligoclase with 

 hornblende and inica) (Curtius, Peloponnesos, Bd. ii, s. 439, 446, 

 tab. xiv). 



75 See the admirable geological map of the district of Schemnitz by 

 Bergrath, Johann von Peltko, 1852, and the Abhandlungen dtr Jc. k. 

 yeologischen Reichsanstalt, Bd. ii, 1855, Abth. i, s. 3. 



76 Cosmos, see above, pp. 401 2. 



77 The basaltic columns of Pisoje, the felspathic part of which has been 

 analysed by Francis (Poggend. Annal. Bd. lii, 1841, s. 471), near the 



banks of the Cauca, in the plain of Amolanga (not far from the Pueblos 

 of Sta. Barbara and Marmato), consist of a somewhat modified oligo- 

 clase in large beautiful crystals, and small crystals of hornblende. 

 Nearly allied to this mixture are, the quartz, containing dioritic-por- 

 phyry of Marmato, brought home by Degenhardt, the felspathic part of 

 which was named by Abich Andesine, the rock, destitute of quartz, 

 of Cucurusape, near Marmato, in Boussingault's collection (Charles 

 Ste.-Cl. Deville, Etudes de Lithologie, p. 29), the rock which I found 12 

 geographical miles eastward of Chimborazo, below the ruins of old 

 lliobamba (Humboldt, Kleinere Scliriften, Bd. i, s. 161), and lastly, the 

 rock of the Esterel Mountains in the department of the Var (Elie da 

 Beaumont, Explic. de la, Carte Geol. de France, t. i, p. 473). 



