xl PJii/sical and Geognostic Suggestions^ 



which I presented in the atlas published in my " Kleine 

 Schriften" (Plate V. p. 461), formerly higher than Chim- 

 borazo, and still (?) 16,380 feet. Not a single specimen of 

 its trachyte has ever been deposited in a European museum. 

 The Altar itself is readily accessible from Riobamba Nuevo. 

 In its vicinity may also be seen mica slate and gneiss, 

 cropping out at the Paramo del Hatillo near Guamote, and 

 Teocaxas, which are so seldom fallen in with in the highlands 

 of Quito. Tradition relates that gold-mines were worked here 

 during the days of the Incas, in the neighbourhood of vol- 

 canic trachytes. From the Altar the geologist might proceed, 

 by way of San Luis, (Query, whether the primitive clay-slate 

 found here be of the Silurian formation ?) and Guamote, to 

 Paramo del Assuay (2428 toises), and Cuenca, as far as 

 Atausca (2*^ 13' S.), where an immense mass of sulphur, lying 

 in a quartz seam is worked, forming a bed in the mica slate. 

 Of what rock does the easily accessible Cayambe UrciJ 

 (18,170 feet) consist, crossing the Equator, S.E. of Otavalo? 

 En route from Quito to Cayambe, the rich deposits of obsi- 

 dian near Quinche should also be inspected, which furnished 

 the large mirrors to the Incas, and farther to the north of 

 which are the volcanoes of Los Pastes, which form a sepa- 

 rate system by themselves. 



For examining the rocks and exploring the volcanoes of 

 Southern Peru and Bolivia — respecting which see the last 

 edition of Pentland's Maps, not those published between 1830 

 and 1848, in which the height of Sorata was indicated at 



