1:20 COSMOS. 



precisely, on the arrangement of the trachytes according to 

 their composition — excites any particular interest, the merit 

 of this classification is entirely due to my friend and Sibe- 

 rian fellow-traveler, Gustav liose. His accurate observa- 

 tion of nature, and the happy combination which he possesses 

 of chemical, crystallo-mineralogical, and geological knowl- 

 edge, have rendered him peculiarly well qualified to promul- 

 gate new views on that set of minerals whose varied but fre- 

 quently recurring association is the product of volcanic ac- 

 tion. This great geologist, partly at my instigation, has with 

 the greatest kindness, especially since the year 1834, repeat- 

 edly examined the fragments which I brought from the slopes 

 of tlie volcanoes of New Granada, Los Pastos, Quito, and the 

 high land of Mexico, and compared them with the specimens 

 from other parts of the globe contained in the rich mineral 

 collection of the Berlin Cabinet. Before my collections were 

 separated from those of my companion Aime Bonpland, Leo- 

 pold von Buch had examined them microscopically with per- 

 severing diligence (in Paris, 1810-1811, between his return 

 from Norway and his voyage to TenerifFe). He had also at 

 an earlier period, during my residence with Gay-Lussac at 

 Rome (in the summer of 1805), as well as afterward in 

 France, made himself acquaintedr- with what I had noted 

 down in my traveling journal on the spot, in the month of 

 July, 1802, respecting certain volcanoes, and in general on 

 the alRnity between volcanoes and certain porphyries desti- 

 tute of quartz.* I preserve, as a memorial which I consider 



tral mountain, perhaps a cone of eruption, is seen in them, as in Lo- 

 gomontanus. In a beautiful sketch of the crater system of -^tna, 

 which my friend Christian Peters, the astronomer (now in Albany, 

 North America), sent me from Fiensburg, in August, 1854, the para- 

 sitic marginal crater, called the Pozzo di Fuoco, which was formed in 

 January,' 1833, on the east-southeast side, and which had several vio- 

 lent eruptions of lava, is distinctly recognizable. 



* The unspecific and indefinite term *' trachyte" (Rauhstein), which 

 is now so generally applied to the rock in which the volcanoes break 

 out, was first given to a rock of Auvergne in the year 1822, by Hauy, in 

 the second edition of his Traite de Mineralogie, vol. iv., p, 579, with a 

 mere notice of the derivation of the word, and a short description in 

 which the older appellations of granite chauffe en "j^acQ of Desmarets, 

 trap-porphyry, and domite are not even mentionedV It was only by 

 oral communication, originating in Ilauy's Lectures in the Jardin des 

 Plantes, that the term " trachyte" was propagated previous to 1822; 

 for example, in Leopold von Buck's treatise on basaltic islands and 

 craters of upheaval, published in 1818; in Daubuisson's Traite de Min-' 

 eralogie^ 1819; and in 'Beudant's important work. Voyage en Hongrie. 

 Prom letters lately received by me from M. Elie de Beaumont, I find 



