Ch. XIV.] 



AGE OF EIFEL VOLCANOS. 201 



brown coal strata were deposited, was drained ; for the disap- 

 pearance of that great body of fresh water may naturally be 

 supposed to have taken place when the country was undergoing 

 great changes in its physical geography. 



Beds and large veins of quartz are found in the Hundsruck, 

 Taunus, and Eifel, the nearest mountain-chains which border 

 this part of the Rhine, and their degradation may have sup- 

 plied the quartz found in this gravel called Kiescl gerolle by 

 the Germans. 



It has been supposed by some writers that the latest volcanic 

 eruptions of the Eifel and Rhine coincided in epoch with the 

 deposition of the Loess before described (chap. xi.). Such an 

 association, if established, would give a comparatively recent 

 date to the most modern igneous eruptions ; but I looked in 

 vain for any clear indications of such a connexion, and all the 

 sections which I saw appeared to indicate the posteriority of 

 the Loess. The integrity of the volcanic cones is, for reasons 

 before explained, a character to which we attach no value. 



We have, therefore, in this region, graywacke covered by 

 brown coal, and some volcanic formations so blended with the 

 latter as to prove the igneous eruptions to have been contem- 

 poraneous. Yet when we endeavour to assign a chronological 

 position to any one part of the series by reference to organic 

 remains, we discover that the evidence is vague and inconclu- 

 sive. I have as yet been unable to obtain satisfactory proof 

 that any one species of fossil animal or plant has been found 

 in the brown coal, or superimposed formations which was com- 

 mon to a tertiary group of known date in any other part of 

 Europe ; whereas the reader will bear in mind that the relative 

 age of different tertiary formations, of which we have before 

 spoken, was usually determined by reference to a comparison of 

 several hundred, often more than a thousand, species of testacea*. 



* A memoir has lately been communicated to the Geological Society of Lon- 

 don, hy Mr. Homer, on the geology of this district. For fuller details consult 

 Noeggerath's Rheinland Westphalen, and the works of Von Dechen, Oyen- 

 hausen, Von Buch, Steininger, Van der Wyck, Scrape, Daubeny, Leonhard, 

 and Hibbert. 



