M. Humboldt on koo Aitempts to ascend Chimborazo. 295 



cognise a lateral eruption of Chimborazo, the origin of the cone 

 must certainly be ascribed to the subterranean forces which, 

 under that mountain, have for thousands of years vainly sought 

 an opening. It is of later origin than the elevation of the great 

 dome-shaped mountain. TheYana-Urcu forms, with the northern 

 hill Naguangachi, a connected eminence in the form of a horse- 

 shoe ; the bow, more than a semicircle, is open towards the 

 cast. There probably lies in the centre of the horse-shoe, the 

 point out of which the black slags have been thrown, that now 

 lie spread far around. We found there a funnel-shaped depres- 

 sion of about 120 feet in depth, in the interior of which there is 

 a small hill, whose height does not equal that of the surround- 

 ing margin. Yana-Urcu probably signifies the .southern culmi- 

 nating point of the old crater-margin, which, at the most, is ele- 

 vated 400 feet above the level of Calpi. Naguangachi signifies 

 the northern lower end. The whole eminence reminds one, — 

 through its horse-shoe form, not in regard to its rock, — of the 

 somewhat higher hill Javirac (el Panecillo de Quito), which 

 rises isolated at the foot of the volcano Pichincha, in the plain of 

 Turubamba, and which, in La Condamine's, or rather Morain- 

 ville's map, is drawn erroneously as a perfect cone. According to 

 the tradition of the natives, and according to old MSS. which the 

 Cacike or Apu of Lican (the Conchocandi) possessed, the vol- 

 canic eruption of the Yana-Urca occurred immediately after 

 the death of the Inca Tupa-Yupanqui : — thus probably in the 

 middle of the 15lh century. Tradition says that a fire-ball, or 

 indeed a star, fell from heaven and set on fire the mountain. 

 Such fables, connecting the fall of aerolites with eruptions are 

 also spread among the tribes of Mexico. The rock of the 

 Yana-Urcu is a porous dark clove-coloured, often entirely black 

 slaggy mass, which may be easily confounded with porous ba- 

 salt. Olivin is entirely wanting in it, the white, sparingly dis- 

 tributed crystals it contains, are throughout small and probably 

 Labrador. Here and there, I saw a sprinkling of iron-pyrites. 

 The whole belongs probably to the black augile-porphyry, as 

 well as the whole formation of Chimborazo, of which we shall 

 speak further on, and to which I am not disposed to give the 

 name trachyte, since it contains no felspar, (with some albite), 

 such as is contained in our trachyte of the Siebcngebirge near 



