58 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



whether from local elevation, or from climatal conditions, there are 

 certain appearances over the whole which imply that at one time the 

 temperature must have been very low, as glacier-action can alone 

 account for the presence of the large angular blocks which occur in 

 the lowest detrital beds of many of the Southern coal-basins. 



This central district of France was continued, and connected by 

 means of the Eastern Pyrenees, with the old land-surface of the 

 Spanish Peninsula. 



In the Vosges mountains we find two distinct levels of coal-growth 

 surfaces ; one immediately beneath the Vosges sandstone, but un- 

 conformable with it, and belonging to the great Coal-measure 

 period, or that of the widest range of terrestrial conditions ; the 

 other subordinate to the slate and limestone series there, and not in 

 conformity with the higher group : this last may perhaps be of the 

 age of the anthracitic seams in the Devonian or Eifelian series, in 

 places contiguous to the land-surfaces of that time, as in Devonshire, 

 the Cotentin, and the Boulonnais*. 



The present depression between the Vosges and Schwarzwald 

 ranges is of very recent date : anterior to this they constituted one 

 group, which comprised the Odenwald in its extension northwards. 



No marine remains have as yet been discovered in the Saarbriick 

 coal group, nor in its extension towards Mayence ; whilst the terres- 

 trial forms which it is constantly affording, as well as the aspect of its 

 sedimentary beds, give it all the essential features of an old lacustrine 

 group, — an internal land-locked area, — of which the deposits have 

 been accumulated over the edges of disturbed older Palaeozoic strata : 

 it has much of the character belonging to the estuaries or deltas of 

 rivers carrying down great quantities of sand, and the cross-bedding 

 which these beds now present suggests that the current was to the 

 S.W., or that the area opened out into the sea in that direction. 

 The great extension which is now being given to the Coal-measures 

 beneath the plain of Lorraine points to the existence of a belt 

 ranging in one direction towards the Vosges, and in the other towards 

 Luxembourg. 



Across the ranges of the Hundsriick and the Ardennes, the great 

 Belgian coal-band presents very different relations to the underlying 

 formations ; it is in ascending sequence, offering the fullest and clearest 

 succession of the Rhenane (Devonian) and Carboniferous groups, and 

 resolving itself ultimately into a vast assemblage of earthy sedimentary 

 strata, which alternate almost indefinitely with terrestrial surfaces. 

 The evidence of this stage of conditions is preserved along a trough 

 more than 150 miles in length, and of singularly disproportionate 

 breadth. The abundance of shells of the genus Unio, at various 

 levels, and overlying the coal-bands, would seem to give a fresh- 

 water character to the whole series, but for the occasional intercala- 

 tion of beds containing OrthoceratUy Goniatites^ Aviculopecten, such 

 as occur in our own Yorkshire series, but which in Belgium range 

 from the Alum-shales, or the base of the Coal-measures, at occasional 

 levels, upwards. 



* Memoires pour servir, &c., par MM. Dufrenoy et E. de Beaumont, vol. i. 



