204 M. Von Buch on Vokanos and Craters of' Elevation, 



light on this subject, as well as on the whole science of geog- 

 nosy, and from this source a new and unexpected view has 

 been obtained of the rocks of vokanos. By means of the con- 

 clusions resulting from these discoveries, and the more exten- 

 sive application of the more exact determinations which have 

 been rendered necessary, a new and entirely unexplored field 

 of investigation has been opened up. I may regard it as 

 one of the not wholly unimportant fruits of our autumn tour, 

 and ' one produced by the discoveries of Rose, that the rock 

 of Etna appeared to us for the first time in its true form and 

 in its true composition. The great abundance of crystals of 

 felspar contained, as I believed, in the lavas of Etna, had in- 

 duced me to assume that the entire volcano consisted, like 

 other volcanoes, of trachyte. And indeed the newest accounts 

 of the latest observers describe the declivities and the interior 

 of the mountain as formed of trachytic rocks. The discove- 

 ries of Rose teach us to adopt another opinion. The entire 

 want of obsidian and of pumice in Etna was of itself an ex- 

 tremely remarkable and striking phenomenon, since, in every 

 other case, trachyte indicates pumice, as, on the other hand, 

 pumice indicates obsidian and trachyte. After many careful 

 investigations in the district of Catania, and on Etna itself, 

 M. Elie de Beaumont and myself were, after much doubt, at 

 length convinced that felspar does not occur in Etna, and there- 

 fore that there is no trachyte. All the streams of lava, as well 

 as all the beds in the interior of the mountain, consist of a 

 mixture of augite and labradorite, and in this respect resemble 

 the dolerite of the basaltic series. But M. de Beaumont is in- 

 clined to think, that the preponderance of labradorite may ren- 

 der a new name necessary for the Etna rock. From such a rock 

 obsidian and pumice were certainly not to be expected. Etna 

 is hence more related to basaltic rocks than to trachyte. It does 

 not at all resemble the Lipari Islands, for some of these are 

 entirely composed of trachyte. The others, on the contrary, 

 viz. Lipari, Volcano, and Salinas, consist almost entirely of pu- 

 mice, or of tufaceous rocks, in which pumice appears as a chief 

 ingredient. It is only the constantly active Stromboli that 

 is again different from these last. It would appear from col- 

 lections, and from the investigations of Professor Friedrich 



