then, of settling this moot point, it also remains for the members of the _Novara_ Expedition to obtain. It would be important to examine the Sangay (16,068 feet)--which, like Stromboli, is in constant activity, yet without any traces of lava-streams--on account of the grains of quartz discovered by Wisse in the trachytic boulders ejected by the volcano, which is of such rare occurrence in the trachytes out of Hungary; and also on account of the close vicinity of beds of granite and gneiss, which are broken through by the Sangay trachyte, forming an island, as it were, of not hardly two miles in breadth. Still more deserving of attention is the extinct volcano El Altar de los Collanes (Capac Urcù) a sketch of which I presented in the atlas published in my "Kleine Schriften" (Plate V. p. 461), formerly higher than Chimborazo, 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 Quitó. Tradition relates that gold-mines were worked here during the days of the Incas, in the neighbourhood of volcanic 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 Urcù (18,170 feet) consist, crossing the Equator, S.E. of Otavalo? _En route_ from Quitó to Cayambe, the rich deposits of obsidian 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 Pastos, which form a separate 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 3949 toises (25,257 feet), and Illimani at 3753 toises (24,004), and accordingly both as much more lofty than Chimborazo, which is 3350 toises (21,426 feet)--the best starting-point would be the port of Arica, which may be reached, sailing the whole distance against the cold current, from Guayaquil, after a short stay at Callao de Lima. Of the volcanoes of Peru and Bolivia only three are now active.