TRUE VOLCANOES. 437 



remains. It would in like manner be unobjectionable to 

 designate trachyte formations after particular mountains — 

 to make use of the expression TenerifFe trachyte or iEtna 

 trachyte for decided oligoclase or Labradorite formations. 

 So long as there was an inclination among geologists to find 

 albite every where among the very different kinds of feldspar 

 which are peculiar to the chain of the Andes, every rock in 

 which albite was supposed to exist was called andesite. I 

 first meet with the name of this mineral, with the distinct 

 definition that "andesite is composed of a preponderating 

 quantity of albite and a small quantity of hornblende," in 

 the important treatise written in the beginning of the year 

 1835, by my friend Leopold von Buch, on " Craters of up- 

 heaval and volcanoes.''* This tendency to find albite every 



* The name of andesite first occurs in print in Leopold von Buch's 

 treatise, read on the 26th March, 1835, at the BerHn Academy. That 

 great geologist Hmits the appellation of trachyte to those cases in 

 which glassy feldspar 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 

 feldspar 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 neighborhood of Catanea and at -^tna, Elie de Beaumont and I 

 have convinced ourselves that feldspar is not to be met with on ^tna, 

 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 

 feldspar^ in which case a new mineral is formed, which can no longer 

 be denominated trachyte. According to G. Rose's (present) investi- 

 gations, it may be considered tolerably certain that not one of the al- 

 most innumerable 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 Humboldt's journeys alone^ 

 with one half of these volcanoes and their products in both hemi- 

 spheres. Through Meyen we are acquainted with these albitiferous 

 minerals in Bolivia and the northern part of Chili ; through Poppig, 

 as far as the southernmost 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 prepon- 

 derance of albite and a small quantity 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 edi- 

 tion of his work on the Canary Islands. The volcanoes Pichincha, 

 Cotopaxi, Tungurahua, and Chimborazo, are all said to consist of an- 

 desite, while the Mexican volcanoes were called genuine (sanidinifer- 



