Cl NOTES. 



(^ p. 422. Like the granitic pieces enveloped in the trachytes of Jorullo. 

 Kosmos, Bd. iv. S. 345 (English edition, present volume, p. 300 301). 



( 5S4 ) p. 422. Also in the Eifel, according to the high authority of Berg- 

 hauptmann von Dechen. Kosmos, Bd. iv. S. 281 (present volume, p. 235). 



( 58S ) p. 422. Kosmos, Bd. iv. S. 357 (present volume, p. 312). The Rio 

 de Guaillabamba flows into the Kio de las Esmeraldas. The village of Guailla- 

 bamba, near which I found the isolated basalts containing olivine, is only 6908 

 feet above the sea. The heat in this valley is extremely oppressive, and it is 

 still worse in the Valle de Chota, between Tusa and the Villa de Ibarra, of 

 which the lowest part is only 5288 feet above the sea, and which may rather be 

 called a deep cleft than a valley, being rather under 9600 feet wide, and fully 

 4800 feet deep. (Humboldt, Kec. d'Observ. astronomiques, vol. i. p. 307.) The 

 eruption of fragments called Volcan de Ansango, on the declivity of Antisana, 

 is not a formation of basalt; they consist of a trachyte containing oligoclase, and 

 bearing some resemblance to a basalt. On the mutual avoidance, or " antago- 

 nisme des basaltes et des trachytes," see my Essai ge'ognostique sur le gisement 

 des Eoches, 1823, p. 348 and 359, and, in general, p. 327336. 



( 588 ) p. 425. Sebastien Wisse, Exploration du Volcau de Sangay, in the 

 Comptes rendns de 1'Acad. des Sciences, t. xxxvi. (1853) p. 721 ; compare also 

 Kosmos, Bd. iv. S. 292, Anm. 40, and S. 301 303 (English edition, p. 248, 

 and Note 364). According to Boussingault, the erupted fragments brought back 

 by Wisse, and which were collected on the upper portion of the declivity of the 

 cone (the traveller reached a height of 960 feet below the summit, which has 

 itself a diameter of 486 feet), consist of a black pitch-like substance, in which 

 are embedded crystals of glassy (?) felspar. A very remarkable phenomenon, 

 unique, I believe, in volcanic eruptions, so far as we are at present aware, is that, 

 together with these large black pieces of trachyte, small angular pieces of pure 

 quartz are erupted. These fragments (according to a letter written, in January 

 1851, by my friend Boussingault) are not more than four cubic centimetres in 

 volume. In the trachytic masses themselves there is no quartz interspersed. 

 All volcanic trachytes which I have examined in the Cordilleras of South 

 America and Mexico, and even those trachytic porphyries in which the rich 

 silver-veins of Real del Monte, Moran, and Regla, north of the high valley of 

 Mexico, occur, are entirely without quartz. Notwithstanding this apparent 

 antagonism between quartz and trachyte in burning volcanoes, I am not in- 

 clined to deny the volcanic origin of the millstone trachytes (trachytes et 

 porphyres meulieres) to which Beudant has justly called attention. The manner 

 in which these have burst forth from fissures is, however, doubtless a mode of 



