234 REACTION OF THE INTERIOR OF THE EARTH 



basaltic mountains or hills; as in the Seilberg (1892 feet 

 high), near Quiddelbach, on the Height of Struth near 

 Kelberg, and in the wall-like ridge of Eeimerath near 

 Boos." 



Next after the Lipari and Ponza Islands few parts of 

 Europe have produced more pumice than this part of 

 Germany, which, with a comparatively small elevation, 

 presents such different forms of volcanic activity, Maars 

 or craters of explosion, basaltic hills, and lava-emitting 

 volcanoes. The principal mass of the pumice is between 

 Niedermendig and Sorge, Andernach and Eiibenach ; 

 the principal mass of the " Duckstein " or Trass (a very 

 recent conglomerate deposited by water) is in the 

 Brohlthal, from its mouth at the Rhine up to Burg- 

 brohl, near Plaidt and Kruft. The trass formation of 

 the Brohlthal contains, besides fragments of graywacke 

 schist and pieces of wood, fragments of pumice which 

 are in no way distinguishable from the superficial 

 covering of the district, and even of the trass itself. I 

 have always doubted, notwithstanding some analogies 

 which the Cordilleras might seem to present, whether 

 the trass could be ascribed to eruptions of mud from 

 the lava-emitting volcanoes of the Eifel. I rather con- 

 jecture, with H. von Dechen, that the pumice was 

 thrown out dry, and that the trass was formed in the 

 same manner as other conglomerates. "There is no 

 pumice in the Siebengebirge, and the great eruption of 

 pumice in the Eifel (the principal mass of which still 

 overlies the Loess, and in parts alternates with it) may, 

 according to the conjecture to which the local relations 

 tend to lead us, have taken place in the valley of the 

 Rhine above Neuwied, in the great Neuwied basin, 



