538 



MIOCENE VOLCANIC ROCKS. 



[Ch. XXXI. 



Germans, which probably belong in part to the Miocene, and in part to 

 the Upper Eocene, epoch. 



This Brown-Coal is seen on both sides of the Rhine, in the neighbor- 

 hood of Bonn, resting unconformably on highly inclined and vertical 

 strata of Silurian and Devonian rocks. Its geographical position, and the 

 space occupied by the volcanic rocks, both of the Westerwald and Eifel, 

 will be seen by referring to the map (fig. 672), for which I am indebted 

 to Mr. Horner, whose residence for some years in the country enabled 

 him to verify the maps of MM. Noeggerath and Von Oeynhausen, from 

 which that now given has been principally compiled.* 



The Brown-coal formation of that region consists of beds of loose sand, 

 sandstone, and conglomerate, clay with nodules of clay-ironstone, and oc- 

 casionally silex. Layers of light brown, and sometimes black lignite, are 

 interstratified with the clays and sands, and often irregularly diffused 



Fig. 672. 



Map of the volcanic region of the Upper and Lower Eifel. 

 12 3 4 5 English miles. 



C • s i ; r 



1-. ■-.>... - | Volcanic J A. of the Upper Eifel. i ^p. l Points of eruption, with craters and 



l'£w& | District ( B. of the Lower Eifel. I tfc ' I scoriae. 



J Trachyte. 



A 1 ". S. The country in that part of the map which is left blank is composed of inclined Silurian 

 and Devonian rocks. 



* Horner, Trans, of Geol. Soc 2d ser. vci v. 



