OX ITS EXTERIOR. VOLCANOES. 233 



Meerfelder Maar, (the latter of which is rich in balls of 

 olivine,) which contain many fine crystalline masses. We 

 will cite here Zircon, Hauyne, Leucite, ( 317 ) Apatite, 

 Nosean, Olivine, Augite, Ryacolite, common Felspar (Or- 

 thoclase), glassy Felspar, Mica, Sodalite, Grarnet, and 

 Titanite. If the number of fine crystallised minerals at 

 Vesuvius is much greater, (Scacchi counts 43 kinds,) 

 it should not be forgotten that very few of them were 

 emitted from the volcano; that the greater part of 

 them belong, according to Leopold von Buch's opinion, 

 ( 318 ) " not to Vesuvius, but to a tufa-covering, extending 

 far beyond Capua, which was upheaved by the cone 

 of Vesuvius together with itself at its elevation, and 

 was probably the product of a submarine volcanic action 

 hidden deep in the interior of the earth." 



Certain determinate directions of the different kinds 

 of phenomena produced by volcanic activity may also be 

 distinctly traced in the Eifel. " The eruptions of lava 

 in the high Eifel took place along a fissure nearly 

 28 miles long, running from south-east to north- 

 west, from Bertrich to the Goldberg near Ormond ; 

 on the other hand, the Maars from the Meerfelder 

 Maar to Mosbruch and the Laacher See follow a direc- 

 tion from south-west to north-east. These two leading 

 lines of direction intersect each other in the three 

 Maars of Daun. Eound the Laacher See no trachyte is 

 visible at the surface. The presence of this rock in the 

 depths below is only indicated by the peculiar nature of 

 the whole felspathic pumice of Laach, as well as by the 

 ejected balls of augite and felspar. The only visible 

 trachytes of the Eifel, however, composed of felspar with 

 large crystals of hornblende, are distributed between 



