TRUE VOLCAN03S. 469 



lasted for five or six years, until renewed investigations of a 



great geologist limits the appellation of trachyte to those cases in which 

 glassy felspar is contained, and thus speaks in the above treatise, 

 which was not printed till 1836 (Poggend. Annal., Bd. xxxvii, s. 

 188 190): "The discoveries of Gustav Rose, relating to felspar, 

 have shed a new light on volcanoes and geology in general, and the 

 minerals of volcanoes have in consequence presented a new and totally 

 unexpected aspect. After many careful investigations in the neigh- 

 bourhood of Catanea and at Etna, Elie de Beaumont and I have con- 

 vinced ourselves that felspar is not to be met with on Etna, and 

 consequently there is no trachyte either. All the lava-streams, as well 

 as all the strata in the interior of the mountain, consist of a mixture of 

 augite and labradorite. Another important difference in the minerals 

 of volcanoes is manifested when albite takes the place of felspar, in 

 which case a new mineral is formed, which can no longer be denomi- 

 nated trachyte. According to G. Rose's (present) investigations, it may 

 be considered tolerably certain that not one of the almost innumer- 

 able volcanoes of the Andes consists of trachyte, but that they all 

 contain albite in their constituent mass. This conjecture seems a very 

 bold one, but it loses that appearance when we consider that we have 

 become acquainted, through Huinboldt's journeys alone, with one-half 

 of these volcanoes and their products in both hemispheres. Through 

 Meyen we are acquainted with these albitiferous minerals in Bolivia 

 and the northern part of Chili; through Poppig, as far as the southern- 

 most limit of the same country ; through Erman, in the volcanoes of 

 Kamtschatka. Their presence being so widely diffused and so distinctly 

 marked, seems sufficiently to justify the name of andesite, under which 

 this mineral, composed of a preponderance of albite and a small quan- 

 tity of hornblende, has already been sometimes noticed." Almost at 

 the same time that this appeared, Leopold von Buch enters more into 

 the detail of the subject in the addenda with which, in 1836, he so 

 greatly enriched the French edition of his work on the Canary Islands. 

 The volcanoes Pichincha, Cotopaxi, Tungurahua, and Chimborazo, are 

 all said to consist of andesite, while the Mexican volcanoes were called 

 genuine (sanidiniferous) trachytes (Description physique des lies Canaries, 

 1836, pp. 486, 487, 490, and 515). This lithological classification of the 

 volcanoes of the Andes and those of Mexico shows that, in a scientific 

 point of view, such a similarity of mineralogical constitution and the 

 possibility of a general denomination derived from a large extent of 

 country, cannot be thought of. A year later, when Leopold von Buch 

 first made mention, in Poggendorjfs Annalen, of the name of Andesite, 

 which has been the occasion of so much confusion, I committed the 

 mistake myself of making use of it on two occasions; once, in 1836, 

 in the account of my attempt to ascend Chimborazo, in Schumacher's 

 Jakrbuch, 1837, s. 204, 205 (reprinted in my Kleinere Schriften, 

 Bd. i, s. 160, 161), and again, in 1837, in the treatise on the high- 

 land of Quito (in Poggend. Ann., Bd. xl, s. 165). "Recent times have 

 taught us," I observed, already strongly opposing my friend's conjecture 

 as to the similar constitution of all the Andes-volcanoes, " that the 



