68 On Red Sandstone. 



of the Hartz, and at the Wintberg mountain, a few miles to 

 the south-west of Dresilen, on the edge of the Dresden coal- 

 field. It is to this overlying formation of red sandstone that, 

 in our opinion, the associated jnesence of large masses of salt 

 and gypsum is exclusively confined. 



The old red sandstone of English geologists, and the moun- 

 tain limestone which covers it, great as is the thickness and 

 importance of each formation, are not recognised in the classi- 

 fication of rocks which Weiner himseH" has drawn up. An 

 example of both these rocks, identical with their types in 

 England, and emerging I'rom 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. Rut 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 prevailing opinion among continental geologists, that 

 tlie grcs 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 nuist have recourse, 

 for the purpose of discrimination, to some of the internal cha- 

 racters 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 indubi- 

 table fragments of old red sandstone, mountain limestone, and 

 the coal-measures, would lead us to refer the disputed forma- 

 tion 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 ex- 

 ))edient of throwing them all together, and regarding them as 

 belonging to one formation of sandstone, in which are con- 

 tained subordinate beds of limestone and coal. This view of 

 the subject may appear at first sight to introduce an advanta- 

 geous 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 hap- 

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

 shire) that the mountain limestone, which usually divides them, 



has 



