538 



MIOCENE VOLCANIC EOCKS. 



[Ch. XXXI. 



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

 the Upper Eocene, epoch. 



This J3rown-Coal is seen on both sides of the Rhine, in the neighbor- 

 hood of Bonn, resting unconforraably 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 Wester wald 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 diftused 



Fig. 672. 



Bmvi 



Map of the Tolcanic region of the Uppei- and Lower Eifel. 

 12 3 4 5 English miles. 

 I : ; : r 



(....-.■ ■. .-.] Volcanic ( A. of the Upper Eifel 



District ( B. of the Lower Eifel. 

 Trachyte. 



Points of eruption, with craters and 



sconce. 

 Basalt. 



E^l Brown coal. 



N". B. The country in that part of the map which is left blank is composed of inclined Silurian 



and Devonian rocks. 



* Horner, Trans, of Geol. Soe. 2d ser. v<l. v. 



