I 



South-western Coal District of England. 315 



Examples of the rothe todte Liegende, or old red sandstone of Werner^ ^ying' 

 over the coal-measures^ may be seen at Norhausen on the borders of the Hartz, 

 and at the Wintberg mountain, a few miles to the south-west of Dresden, on 

 the edge of the Dresden coal-field. It is to this overlying formation of red 

 sandstone that, in our opinion, the associated presence of large masses of salt 

 and gypsum is exclusively confined. 



The old red sandstone of English geologists, and the mountain limestone 

 w^hich covers it, great as is the thickness and importance of each formation, 

 are not recognised in the classification of rocks which Werner himself has 

 drawn up. An example of both these rocks, identical with their types in 

 England and emerging from beneath the coal-measures, may be seen at Huy 

 in the district of the Meuse, between Namur and Liege. 



The millstone grit affords the best example in the south-western coal-field of 

 a red sandstone belonging to the coal-measures. But occasionally even in this 

 coal-field, and very frequently in the coal-districts on the continent, all the coal- 

 grits acquire a red colour; and for this reason we now find it to be the pre- 

 vailing opinion among continental geologists, that the gres rouge is a member 

 of the coal-formation. 



It is by their relative position to one another as well as to other rocks, that 

 these sandstones are best to be distinguished ; but when these points remain 

 obscure, we must have recourse, for the purpose of discrimination, to some of 

 the internal characters detailed in the preceding memoir ; such, for instance, 

 as can be observed in the conglomerate beds from the nature of their imbedded 

 fragments, which, should they be indubitable fragments of old red sandstone, 

 mountain limestone, and the coal-measures, would lead us to refer the disputed 

 formation to the newer red sandstone. 



The distinguishing characters and relative position of these three formations 

 of red sandstone having been only partially attended to, and much confusion 

 having thence arisen, — in order to remove it, an eminent geologist has proposed 

 the expedient of throwing them all together, and regarding them as belonging 

 to one formation of sandstone, in which are contained subordinate beds of 

 limestone and coal. This view of the subject may appear at first sight to in- 

 troduce an advantageous simplification ; but for the following reasons we 

 cannot consent to adopt it. 



With regard to the grits of the coal-measures and of the old red sandstone, 

 since they lie conformably to one another, it may sometimes perhaps be found 

 convenient, in an extended sense, to class them under one formation ; and 

 should it happen that both are of a red colour, and (as is the case in Shrop- 

 shire) that the mountain limestone, which usually divides them, has disap- 



