142 



TRAVELS AMONGST THE GREAT ANDES. 



WESTERN ANDES. 



CoTOCACHi. Hyperstheniferous au- 

 yite-andesite. 



PiCHiNCHA. Highest peak, chiefly 

 hornblende - andesites. Second peak 

 (Rucu - Pichincha) hyperdhe7iifero'u.'< 

 augite-andedtes. 



CoRAZOX. Augite-midesites, usually 

 hyperstheniferous ; in one case (summit 

 ridge) rather rich in this mineral. 



Illiniza. Few si^ecimens. The be.st 

 preserved a hornUendic mtgite-andesite, 

 with some mica and hypersthene. The 

 summit rock a micaceous andesite. 



Carihuairazo. Summit rock aii- 

 (/ite-andesite, perhaps hyperstheniferous. 



Chimborazo. Augite - andesites, 

 generally hyj^erstheniferous; sometimes 

 almost entitled to be called a hypier- 

 stheneandesite. Occasionally hm-n blende 

 is also present. 



EASTERN ANDES. 



Cayambe. Generally a ugite-andesite, 

 but with considei'able minor varia- 

 tions of the pyroxenic constituent ; 

 best general term hornhlendic augite- 

 andesite : one a mica-andesite. 



Antisana. The main mass of the 

 mountain augite -andesites, sometimes 

 hyperstlieniferous. From an outlying 

 part of the mountain come some pitch- 

 stones, pi'ol)ably very glassy dacite. 



SiNCHOLAGUA. Aiujite - andesite, 

 probaljly hyperstheniferous. 



CoTOPAXi. Hyperstheniferous augite- 



andesite. 



Altar. Augite-andesites, probal)ly 

 in general hyperstheniferous. Some of 

 the rocks seem to come nearer to 

 basalt in their composition than is 

 usual in these .specimens from the 

 Ecuadorian Andes. 



Saia-urcu, the only non-volcanic peak ascended by Mr. Whymper, lies to 

 the east, rather to the south-east of Cayambe. Among its rocks are varieties 

 i)f mica-schists and fine-grained gneisses, and a sjjecimen of 'spotted schist,' 

 ccmsisting chiefly of small crystals of mica, and a mineral or minerals belong- 

 ing to the lum-alkaline alumina silicates. I am a little doubtfid whether the 

 felspar-like mineral in the so-called gneisses may not be rather kyanite or 

 some kindred mineral. So far as I can judge from the lithological characters 

 of the rocks I slioidd regard them as Archican, and comi)are them Avith the 

 definitely bedded schists, which usually belong to the nuddle or u]>])er ])art 

 of that great series. 



Mr. Wliymper nowhere saw crystalline igneous rock in the mountain 

 region of the Andes. From a boulder in a stream at the western margin he 

 lirought a specimen of tonalite (or quartz-diorite) ; and from the district east 

 of that visited l)y him he secui'ed a sjiecimen of granite. 



He brought back a considerable series of specimens of volcanic dusts from 



