MAARS. 225 



opinion of Leopold von Buch,* "are quite foreign to Vesu- 

 vius, and to be referred to a tufaceous covering diffused far 

 beyond Capua, which was- upheaved by the rising cone of 

 Vesuvius, and has probably been produced by a deeply-seat- 

 ed submarine volcanic action." 



Certain definite directions of the various phenomena of 

 volcanic activity are unmistakable 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- 

 rich to the Goldberg, near Ormond, directed from southeast 

 to northwest ; on the other hand, the Maars, from the Meer- 

 felder Maar to Mosbruch and the Laacher lake, follow a line 

 of direction from southwest to northeast. These two pri- 

 mary directions intersect each other in the three Maars of 

 Daun. In the neighborhood of the Laacher lake trachyte 

 is nowhere visible on the surface. The occurrence of this 

 rock below the surface is only indicated by the peculiar na- 

 ture of the perfectly feldspar-like pumice-stone of Laach, 

 and by the bombs of augite and feldspar thrown out. But 

 the trachytes of the Eifel, composed of feldspar and large 

 crystals of hornblende, are only visibly distributed among 

 basaltic mountains: as in the Sellberg (1893 feet), near 

 Quiddelbach ; in the rising ground of Struth, near Kelberg ; 

 and in the wall-like mountain chain of Reimerath, near 

 Boos." 



Next to the Lipari and Ponza islands few parts of Europe 

 have probably produced a greater mass of pumice-stone than 

 this region of Germany, which, with a comparatively small el- 

 evation, presents such various forms of volcanic activity in its 

 Maars (cratcres cV explosion}, basaltic rocks, and lava-emitting 

 volcanoes. The principal mass of the pumice-stone is situ- 

 ated between Nieder Mendig and Sorge, Andernach and Rii- 

 benach ; the principal mass of the ductetein, or Trass (a very 

 recent conglomerate, deposited by water), lies in the valley 

 of Brohl, from its opening into the Rhine upward to Burg- 

 brohl, near Plaidt and Kruft. The Trass formation of the 

 Brohl valley contains, together with fragments of graywacke- 

 slate and pieces of wood, small fragments of pumice-stone, 

 differing in nothing from the pumice-stone which constitutes 

 the superficial covering of the region, and even that of tho 



* Leopold von Buch, in Poggend., Annalen, bd. xxxvii., s. 179. Ac- 

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

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

 1853, s. 259. 



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