26 Murchisoris Silurian System. 



limestone, generally rounded and red on their exterior. 

 Some of them are of an oolitic structure ; others a compact 

 limestone, containing encrimites, corals, and terebratulae, and 

 discoloured, partly by films of green carbonate of copper ; 

 secondly, conglomerate with fewer fragments of limestone 

 but containing pebbles of quartz, old red sandstone, &c. ; 

 the whole cemented by pure white crystallized carbonate 

 of lime. This conglomerate passes into a pink calcareous 

 sandstone, with pebbles and minute fragments of jasper. 



" In attempting to refer the fragments of limestone to the 

 original rock, the oolitic structure distinctly proves that some 

 of them have not been derived from any formation below the 

 Old Red Sandstone, while the nearest known masses of a 

 similar rock are in the carboniferous limestone of the Clee 

 hills, twenty miles distant. The included fossils belong like- 

 wise to the same deposit, while the rolled condition of the 

 fragments, accords with the idea of their having been drifted 

 from the quarter alluded to. At Coal-Brook Dale coal-fields 

 the conglomerate is not sufficiently calcareous to be burnt 

 for lime, being chiefly composed of rounded fragments of 

 sandstone and quartz, with some fragments of carboniferous 

 limestone, in a base of quartzose and calcareous sand. 

 Here, as in other localities before mentioned, the strata dip 

 away from the adjacent coal-field, from which, as we shall 

 afterwards perceive, they are separated by a great fault. The 

 extensive denudation of the whole series of the New Red 

 System between Newport and Shrewsbury, has obliterated 

 all traces of the calcareous conglomerates, which are not 

 met with again till we approach Shrewsbury where a small 

 face of the rock can be seen, which was formerly quarried 

 to burn for lime, but is rapidly lost, dipping to about 

 30° under the sandstone. To the north and west of this 

 spot, the relations to the various members of the New Red 

 System, which overlie the coal bearing strata of Poutes- 



