MAARS. 235 



Maar so rich in bombs of olivine, contain fine crystallized 

 masses. We may here mention, zircon, hauyne, leucite, 93 apa- 

 tite, nosean, olivine, augite, rhyacolite, common felspar 

 (orthoclase) , glassy felspar (sanidine), mica, sodalite, garnet, 

 and titanic iron. If the number of beautifully crystallized 

 minerals on Vesuvius be so much greater (Scacchi counts 

 43 species), we must not forget, that very few of them are 

 ejected from the volcano, and that the greater number belongs 

 to the portion of the so-called eruptive matters of Vesu- 

 vius, which, according to the opinion of Leopold von Buch, 94 

 " are quite foreign to Vesuvius, and to be referred to a 

 tufaceous covering diffused far beyond Capua, which was up- 

 heaved by the rising cone of Vesuvius, and has probably 

 been produced by a deeply-seated submarine volcanic action." 

 Certain definite directions of the various phenomena of 

 volcanic activity are unmistakeable even in the Eifel. " The 

 eruptions, producing lava-streams, of the upper Eifel lie in 

 one fissure, nearly 32 English miles in length, from Bert- 



93 Leucite (of the same kind from Vesuvius, from Rocoa di Papa in 

 the Albanian mountains, from Viterbo, from the Rocca Monfina, 

 according to Pilla, sometimes of more than 3 inches in diameter, and 

 from the dolerite of the Kaiserstuhl in the Breisgau), occurs also " in 

 position as leucite-rock in the Eifel, on the Burgberg, near Rieden. 

 The tufa in the Eifel incloses large blocks of leucitophyre near Boll 

 and Weibern." I cannot resist the temptation to borrow the following 

 important observation from a chemico-geognostic memoir read by Mits- 

 cherlich a few weeks since before the Academy of Berlin. "Aqueous 

 vapours alone may have effected the eruptions of the Eifel ; but they 

 would have divided olivine and augite into the finest drops and pow- 

 der, if they had met with them in a fluid state. With the funda- 

 mental mass of the erupted matters fragments of the old, broken up rock 

 are most intimately mixed, for example on the Dreiser Weiher, and 

 these are frequently caked together. The larger olivine masses and the 

 masses of augite even usually occur surrounded by a thick crust of 

 this mixture ; a fragment of the old rock never occurs in the olivine or 

 augite, both were consequently formed before they reached the spot 

 where the breaking up took place. Olivine and augite had therefore 

 separated from the fluid basaltic mass before this met with an accumu- 

 lation of water or a spring which caused its expulsion." See also upon 

 the bombs an older memoir by Leonard Homer, in the Transactions of 

 the Geological Society, 2nd series, vol. iv, pt. 2, 1836, p. 467. 



94 Leopold von Buch, in Poggend. Annalen, Ed. xxxvii, s. 17P. 

 According to Scacchi, the eruptive matters belong to the first outbreak 

 of Vesuvius in the year 79. Leonhard's Neues Jahrbuch fur Mineral 

 1853, s. 259. 



