TRUE VOLCANOES. 239 



The volcano of Purace* near Popayan: 17,010 feet, according to 

 Jose Caldas. 



Fifth group, from 16,000 to more than 20,000 Fans or from 

 17,056 to 21,320 English feet in height. 



The volcano Sangai/-, to the southwest of Quito: 17,128 feet, ac- 

 cording to Bouguer and La Condamine.f 



The \o\cano Popocatepetl :X 17,729 feet, according to a trigonomet- 

 rical measurement by Humboldt. 



The volcano of Orizaba:^ 17,783 feet, according to Ferrer. 



Elias MountW (on the west coast of North America): 17,855 feet, 

 according to the measurements of Quadra and Galeano. 



the earthquake of Riobamba (1797), which gave rise to great depres- 

 sions of mountains. In the year 1802 I found the summit of the 

 volcano trigonometrically to be only 16,494 feet. 



* The barometrical measurement of the highest peak of the Volcan 

 de Purace by Francisco Jose Caldas, who, like my dear friend and 

 traveling companion, Carlos Montufar, fell a sacrifice to his love for 

 the independence and freedom of his country, is given by Acosta 

 {Vlajes Clentificos, p. 70) at 5184 metres (17,010 feet). I found the 

 height of the small crater, which emits sulphureous vapors with a 

 violent noise (Azufral del Boqueron), to be 14,427 feet ; Humboldt, 

 Recudl d Observ. Astronomiques et d^ Operations Trigonoinctriques, vol. i., 

 p. 304. 



t The Sangay is extremely remarkable from its uninterrupted ac- 

 tivity and its position, being removed somewhat to the eastward from 

 the eastern Cordillera of Quito, to the south of the Rio Pastaza, and 

 at a distance of 120 miles frqp the nearest coast of the Pacific — a 

 position which (like that of the volcanoes of the Celestial mountains 

 in Asia) by no means supports the theory according to which the east- 

 ern Cordilleras of Chili are free from volcanic eruptions on account 

 of their distance from the sea. The talented Darwin has not omitted 

 referring in detail to this old and widely diffused volcanic littoral 

 theory in the Geological Observations on South America, 1846, p. 185. 



X I measured Popocatepetl, which is also called the Volcan Grande 

 de Mexico, in the plain of Tetimba, near the Indian village San Nico- 

 las de los Ranchos. It seems to me to be still uncertain which of the 

 two volcanoes, Popocatepetl or the peak of Orizaba, is the highest 

 (see Humboldt, Eeceuil d^Observ. Astron., vol. ii., p. 543). 



§ The peak of Orizaba, clothed with perpetual snow, the geographic- 

 al position of which was quite erroneously indicated on all maps be- 

 fore my journey, notwithstanding the importance of this point for navi- 

 gation near the landing-place in Vera Cruz, was first measured trigo- 

 nometrically from the Encero by Ferrer, in 1796.. The measurement 

 gave 17,879 feet. I attempted a similar operation in a small plain 

 near Xalapa. I found only 17,375 feet, but the angles of elevation 

 were very small, and the base-line difficult to level. See Humboldt, 

 Essai Politique sur la Nouv. Espagne, 2me ed.,t. i., 1825, p. 166 ; Atlas 

 du Mexique (Carte des fausses positions), pi. x., and Kleinere Schriften, 

 bd. i., s. 468. 



Ii Humboldt, Essai sur la Geograplde des Plantes, 1807, p. 153. The 

 elevation is uncertain, perhaps more than -jl^th too high. 



