4G8 COSMOS. 



In these considerations on the individual diversity of tho 

 mineralogical constitution of neighbouring volcanoes, we find 

 a condemnation of the mischievous attempt to introduce a 

 name for a species of trachyte, derived from a mountain- 

 chain, chiefly volcanic, of more than 7200 geographical miles 

 in length. The name of Jura limestone, which I was the 

 first to introduce, 8 ^ is unobjectionable, because it is taken 

 from a simple unmixed rock ; from a chain of mountains 

 whose antiquity is characterised by its containing organic 

 remains. It would in like manner be unobjectionable to 

 designate trachyte-formations after particular mountains, 

 to make use of the expression Teneriffe-trachyte or Etna- 

 trachyte for decided oligoclase or labradorite formations. 

 So long as there was an inclination among geologists to find 

 albite everywhere among the veiy different kinds of felspar 

 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 upheaval 

 and volcanoes"** This tendency to find albite every where 



84 In the course of a geological tour which I made, in 1795, through 

 the south of France, western Switzerland, and the north of Italy, I had 

 satisfied myself that the Jura limestone, which Werner reckoned among 

 his Muschel-kalk, constituted a peculiar formation. In my treatise 

 on subterranean gases, published by my brother, Wilhelm von Hum- 

 boldt, in 1799, during my residence in South America, this formation, 

 which I provisionally designated as Jura limestone, was for the first 

 time mentioned (s. 39). This account of the new formation was imme- 

 diately transferred to the Oberbergrath Karsteu's miueralogical table?, 

 at that time so generally read (1800, p. 64, and preface, p. vii), I named 

 none of the petrifactions which characterise the Jura formation, and in 

 relation to which Leopold von Buch has acquired so much credit 

 (1839) ; I erred likewise in the age ascribed by me to the Jura forma- 

 tion, supposing it to be older than muschel-kalk, on account of its 

 propinquity to the Alps, which were considered older than Zechstein. 

 In the earliest tables of Bucklancl, on the Superposition of strata in the 

 British Islands, the Jura limestone of Humboldt is reckoned as belong- 

 ing to the upper oolite. Compare my Essai Geogn. sur le Gisement des 

 Roches, 1823, p. 281. 



85 The name of Andesite first occurrs in print in Leopold von Buch's 

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



