60 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



the older subjacent series : in this way our own Wealden area, as 

 well as the districts around it, may be made to indicate the arrange- 

 ment of the Palaeozoic strata beneath. 



The district of old sedimentary strata which bounds the coal-band 

 of Belgium on the S. from Aix-la-Chapelle westwards gradually sub- 

 sides and disappears beneath the Cretaceous series of deposits along 

 a line from Valenciennes to Hirson, which runs somewhat transversely 

 to the direction of the old range. This feature is due to a subsidence 

 of post-cretaceous date, for the continuity of the coal-band is in no 

 way affected by it ; and, though the symmetrical form and direction 

 of the trough are disturbed at Valenciennes, the pheenomena which 

 the workings present there are just such as would be caused by the 

 passage of a line of fracture and flexure. Whoever has examined the 

 line along which the old series disappears from Quievrain south, must 

 feel satisfied that all the folds which it presents in the district 

 "entre Sambre et Meuse" are continued on beneath the Lower Ter- 

 tiary and the Cretaceous series of the adjoining part of France. 



Subsequently to the formation of the folds or undulations here 

 imparted to the Devonian and Carboniferous beds, the surface of the 

 district became worn down, by a process for which it would be diffi- 

 cult to account or explain ; and this took place prior to the super- 

 position of the Cretaceous series. This appearance is met with again 

 in the Boulonnais, with this difference only, that the Oolitic deposits 

 there rest on the tabular surfaces of the folded Palseozoic series. 

 English geologists are familiar with a like form of surface, with rela- 

 tion to the Oolitic series about Frome. 



The form of the area in which the Carboniferous series was accu- 

 mulated has already been indicated. The position of the coal-measures 

 on the S. of the Hundsriick, where, in a trough parallel to the chain, 

 they rest unconformably on Devonian or Rhenane strata, shows that 

 the broad series of undulations which, commencing with the Hunds- 

 riick, are carried on through the Eifel and the Ardennes, the Condros 

 and down into the Belgian coal-basin, must have had their origin on 

 the S.E. before the commencement of the Carboniferous deposits on 

 the N.W., the consequence of which is that over the French portion of 

 the Carboniferous area its deposits are found resting unconformably. 

 This transgressive passage of the uppermost portions of the Palaeozoic 

 group over the lower from N. to S., and which probably determines 

 the condition and age of the beds ranging beneath the great Paris 

 basin, is altogether distinct from the causes which have produced the 

 arrangement of old surface beneath the Chalk axis of Artois. 



The valley of the Meuse from Liege west presents a line of frac- 

 ture, along which beds of the age of the Devonshire shales and lime- 

 stones are brought to the level of the Coal-measures by great vertical 

 faults, or else narrow ridges of still lower portions of the series are 

 thrust up. It is owing to this that there is that want of uniformity 

 and regular succession on the S. of the Belgian coal-field, which is 

 to be observed on the N. This great line of disturbance can be 

 traced as far as Quievrain, and has been proved by the works of the 

 Valenciennes district. From this place the character of the older 



