older Deposits of the North of Germany and Belgium. 267 



PART II. 



(Map, Plate XXIV., and PI. XXIIL, Sect. 10, 12, 13 and 14.) 



Older Formations on the left Bank of the Rhine, ^c. 



We now proceed to describe the older formations on the left bank of the Rhine, 

 including under that name, — 1st. All the formations between the great coal-field of 

 Belgium and the south-eastern tianks of the Ardennes. 2ndly. The rocks of a 

 corresponding age which extend from the coal-field of Liege to the Eifel. 3rdly. 

 Those from the ridge of the Eifel to the chain of the Hundsriick. The great tract 

 of country we are considering is bounded to the north-west by the coal-fields of Liege 

 and Namur; to the S.W. and S, by the secondary rocks of the upper Meuse, and a 

 part of the basin of the Moselle; to the S,E. by the great Saarbriich coal-field of the 

 Palatinate; and to the E. and N.E. by the valley of the Rhine between Bingen and 

 Bonn. It would hardly have been possible for us during one summer to make out 

 the natural groups of rocks, and their relative age, in such a great and intricate 

 country ; but this task had already been accomplished by Professor Dumont, as far 

 as regards the successive groups between Namur and the chain of the Ardennes 

 on one side, and between Li^ge and the country of the Eifel on the other. It is only 

 in describing the formations between the Eifel and the Hundsriick, and the various 

 groups of rock which appear on the left bank of the Rhine between Bonn and 

 Bingen, that we have to rest chiefly on our own personal observations. 



Carboniferous Rocks of Belgium. 



The coal-field of Belgium, like the coal-field of Westphalia, is bounded to 

 the north by overlying cretaceous and tertiary deposits : but in endeavouring 

 to connect the respective coal-fields with the inferior formations, we meet with 

 incomparably greater difficulties in Belgium than are presented by the traverses 

 through the regularly descending sections of the parts of Westphalia we first 

 examined. These difficulties arise out of the enormous derangements of the 

 strata ; for not only are they violently contorted ; but being often elevated through 

 vertical angles of more than 90°, their relative position, as seen on the natural sec- 

 tions, become inverted, and we can no longer trust our ordinary criterion of super- 

 position. For example, in crossing the Ardennes, we found between Arlon and 

 Bastogne a prevailing dip to the S.S.E. ; but, after reaching what we at first sup- 

 posed the centre of the chain, we in vain looked for a mineral axis indicated by a 

 reversed dip. The prevailing dip continued the same even to the confines of the 

 Belgian coal-field ; nor did the difficulty end there, for, with local exceptions, the 

 whole southern skirt of the Li^ge coal-field is in a reversed position. Hence we 

 might establish a series of vertical sections ; from which, if we had no other evi- 



