older Deposits of the North of Germany and Belgium. 225 



Moselle, to the calcareous formations of the Eifel. We afterwards connected the 

 Eifel with the coal formation of Belgium ; and we twice crossed the chain of the 

 Ardennes, continuing our traverses as far as the secondary strata which skirt its 

 south-eastern flank from Mezieres to Luxemburg. 



As the general result of these observations we may state, that the successive 

 descending groups or systems, between the carboniferous series of Belgium and the 

 oldest rocks seen on any of the last-mentioned traverses, appeared to correspond 

 very exactly with the successive groups (already noticed) on the other bank of 

 the Rhine between Westphalia and the Taunus. 



In making out the succession and relative age of the older rocks within the 

 limits of Belgium, we could do little more than tread in the steps of Professor 

 Dumont ; whose admirable memoir on the coal-field of Liege*, and whose subse- 

 quent papers explaining the structure of the great slaty region which extends from 

 the coal-field of Liege to the Eifel and the Ardennes, are well known to the mem- 

 bers of this Society! . While offering our homage to that geologist for the accuracy 

 of his complicated sections, and for his able determination of a succession of natu- 

 ral groups of strata, we differ from him considerably, as will be seen in the sequel, 

 in our mode of translating them into their British equivalents. The Society will 

 bear in mind, that our leading object was to make out whether (within the country 

 we examined) there was, below the carboniferous limestone, any group of rocks 

 containing fossils of a type intermediate between those of the carboniferous and 

 Silurian systems. The phsenomena on the Westphalian frontier had led us to 

 answer this question in the affirmative. But judging from the successive systems 

 of Belgium, Professor Dumont had before answered it in the negative ; maintaining 

 that there was in his district an immediate passage from the carboniferous to tiie 

 Silurian system. 



In commencing observations such as those on which we were employed last 

 summer, the great point is the determination of good base-lines, to which the 

 ascending or descending groups may be referred in the natural sections. We at 

 first thought ourselves justified in assuming that the whole of the great calcareous 

 zone of Westphalia was the exact equivalent of our mountain limestone. In doing 

 this we were, however, misled by the geological maps of Germany ; even by that 

 of Von Dechen, which had been just published. For we afterwards found that 

 there are in Westphalia two distinct calcareous zones ; the upper (of comparatively 

 small extent on the published maps) representing the true mountain limestone ; 

 the lower (extending from the right bank of the Rhine to Hessia) being both 



* Memoire sur la Constitution Geologique de la Province de Liege, &c. Bruxelles, 1832. 

 I Bulletin de la Societe Geologique de France, tome viii. p. 77? 1836. 



