32 Murchisons Silurian System. 



4. Lower New Red Sandstone. — Foreign Synonyms: 

 Rothe-tode liegende (Ger.) Gres des Vosges couches itife- 

 rieures. (Fr.) 



" When fully developed, as in the tracts of Worcestershire, 

 Staffordshire, and Shropshire, where I shall now describe 

 it, this formation differs essentially in lithological struc- 

 ture from any rocks we have previously considered. 

 As a mass it may be said to consist of sandstones 

 and grits, chiefly of a red colour, sometimes argillaceous, 

 very frequently calcareous, associated with deep brown red 

 shales and marls, occasionally spotted green. Grains of 

 whitish, decomposed felspar are frequent in a matrix of 

 dull red sandstone, iron in various states is here and there 

 disseminated, and bands of impure concretionary and mottled 

 limestone re-occur at various levels. Towards the base, 

 many fragments of impressions of plants appear in beds of 

 sandstone, which graduate into other and lower strata, 

 containing thin seams of coal, from which there is a con- 

 formable descending passage into the true carboniferous 

 system. In general these rocks contain much argillaceous 

 matter, which on decomposing gives a striking resemblance 

 in the surface of the country to those tracts which are 

 occupied by the Old Red Sandstone ; whilst some of 

 the calcareous bands above mentioned are associated 

 with hard flagstones. So completely, indeed, do these 

 bands resemble the cornstone of the Old Red Sand- 

 stone, that they were formerly described from a part of this 

 very tract as belonging to that formation. There is now, 

 however, no doubt respecting their age, since besides their 

 clear superposition to the coal measures, some of these beds 

 contain fragments of mountain limestone, and sandstone 

 with coal plants. This is one of the many proofs (ample 

 testimony of which will be found throughout this volume,) of 

 the danger of testing the age of rocks by any peculiarity in 

 their mineral character, however striking : for the graphic 

 description of the cornstone of the Old Red Sandstone, 



