230 REACTION OF THE INTERIOR OF THE EARTH 



by Abich. In the Eifel volcanoes, two kinds of volcanic 

 activity, of very different age, must be carefully distin- 

 guished from each other, the strictly so-called volcanoes, 

 sending forth streams of lava, and the feebler explosion 

 phenomena of the Maars. To the first belong the 

 basaltic, oliviniferous, vertically columnar lava-stream 

 in the Uesbach valley near Bertrich ; ( 315 ) the volcano of 

 Grerolstein, situated in a limestone containing dolomite, 

 embedded in the Devonian grauwacke schist ; and 

 the long ridge of the Mosenberg (1753 feet above the 

 sea) not far from Bettenfeld, west of Manderscheid. 

 The last-named volcano has three craters, of which the 

 first and second (the northernmost ones) are perfectly 

 round, and their floors covered with turf-bog ; but from 

 the third (southernmost) ( 316 ) crater there has descended 

 a considerable reddish brown stream of lava, which 

 lower down, towards the valley of the Little Kyll, has 

 become columnar. A remarkable phenomenon, generally 

 speaking quite foreign to lava-yielding volcanoes, is, that 

 neither at the Mosenberg, nor at the Grerolstein, nor in 

 the other volcanoes proper of the Eifel, are the lava 

 streams seen to be surrounded at their origin by a 

 trachytic rock, but on the contrary, so far as they are 

 accessible to observation, they seem to come directly 

 from the Devonian beds. The surface of the Mosen- 

 berg in no way betrays what is hidden in its depths. 

 The augitic scoriae, which pass connectedly into basaltic 

 streams, contain small burnt pieces of schist, but no 

 trace of enclosed trachyte. Nor are any such enclosures 

 to be found even in the crater of the Kodderberg, though 

 it is so near to the greatest mass of trachyte in the 

 neighbourhood of the Ehine, the Siebengebirge. 



