122 The Andes and the Amazon. 



capped with trachyte and porphyry.* Large masses of solid 

 rock are rarely seen ; every thing is cracked, calcined, or 

 triturated. While in Bolivia the Eastern Cordillera shovi^s 

 a succession of sharp, ragged peaks, in contrast with the 

 conical summits of the Cordillera of the coast, there is no 

 such distinction in the Andes of the equator.f The Eastern 

 Cordillera has a greater mean height, and it displays more 

 volcanic activity. Twenty volcanic mountains surround the 

 valley, of which twelve are in the oriental chain. Three 

 of the twenty are now active (Cotopaxi, Sangai, and Pichin- 

 cha), and five others are known to have erupted since the 

 Conquest (Chiles, Imbabura, Guamani, Tunguragua, and 

 Quirotoa). The truncated cone of Cotopaxi, the jagged, 

 xllpine crest of ruined Altar, and the dome of Chimborazo, 

 are the representative forms of the volcanic summits. The 

 extinct volcanoes usually have double domes or peaks, while 

 the active peaks are slender cones. Antisana and Cayam- 

 bi are fashioned after Chimborazo, though the latter is ta- 

 ble-topped rather than convex ; Caraguairazo, Quirotoa, Ili- 

 niza, Sincholagua, Euminagui, and Corazon, resemble Al- 

 tar; Tunguragua, Sangai, Llanganati, Cotocachi, Chiles, and 

 Imbabura, imitate Cotopaxi ; Pichincha, Atacatzo, and Gua- 

 mani are irregular. The Ecuadorian volcanoes have rarely 

 ejected liquid lava, but chiefly water, mud, ashes, and frag- 

 ments of trachyte and porphyry. Cotopaxi alone produces 



■ * "As a general rule, whenever the mass of mountains rises much above 

 the limit of perpetual snow, the primitive rocks disappear, and the summits 

 are trachyte or trappean porphyry."— Humboldt'. In general, " the great 

 Cordilleras are formed of innumerable varieties of granites, gneiss, schists, 

 hornblende, chloritic slates, porphyries, etc., and these rocks alternate with 

 each other in meridional bands, which in the ridges frequently present the ap- 

 pearance of a radiated or fan-shaped stracture, and under the plains are more 

 or less vertical." — Evan Hopkins, F.G.S. 



t VonTschudi makes the incorrect statement that " throughout the whole 

 extent of South America there is not a single instance of the Western Cordil- 

 lera being intersected by a river. " Witness the Esmeraldas. 



