194 
OLDER PLIOCENE PERIOD. 
[Ch. XIV. 
English Miles. 
1 2 3 4 5 
No. 48. 
E >;. : . : .vi Volcanic! A, Upper" Eifel. I @ | Points of eruption, with craters 
District J B, Lower Eifel. ^ and scoria?. 
|»^,| Basalt. 
f \ Brown coal. 
if Trachyte. 
N.B. The country in that part of the map which is left blank is almost 
entirely composed of graywacke. 
There has been a long succession of eruptions in this 
country, and some of them must have occurred when its 
physical geography was in a very different state, while others 
have happened when the whole district had nearly assumed 
its present configuration. 
The fundamental rock of the Eifel is an ancient secondary 
sandstone and shale, to which the obscure and vague appella- 
tion of ' graywacke ' has been given. The formation has 
precisely the characters of a great part of those grey and red 
sandstones and shales which are called « old red sandstone ' in 
