Murchison's Silurian System. 535 



the results of his own observation whenever he may be placed 

 in circumstances favourable for prosecuting inquiry. 



Old Red System. 



Having followed Mr. Murchison through the coal mea- 

 sures, as well as the rocks which repose upon them, we shall 

 now endeavour to afford a view of the results of his obser- 

 vations on the more ancient rocks. The old red sandstone 

 consists of various strata, of conglomerate, sandstone, marl, 

 limestone, and tilestone, the newest beds of which dip 

 conformably beneath the coal formation, whilst the oldest 

 repose upon and pass into certain grey coloured rocks, which 

 form the upper part of the Silurian system. 



Convinced that the old red sandstone is of greater magni- 

 tude than any of the overlying groups, Mr. Murchison 

 applies to it the term system, which in geology now implies 

 various groups or formations of strata, indicative of so many 

 distinct periods. Previous geological writers have generally 

 regarded the old red sandstone as a portion of the coal for- 

 mation, from which it is completely distinguishable both by 

 lithological characters and zoological contents. The coal 

 measures, or carboniferous system, Mr. Murchison therefore 

 proves to be surmounted by one red group, and to repose on 

 another, from both of which the coal measures are perfectly 

 distinct, constituting of themselves a distinct system. 



The reason why the old red sandstone has not been 

 regarded as a distinct system Mr. Murchison thinks, is, that 

 in France and Germany its equivalents are ill, if at all, deve- 

 loped. It has however been recognised in Poland and 

 Silesia, while in Norway there are mountain ranges very simi- 

 lar in structure to the old red sandstone of the north of Eng- 

 land, Scotland, and Ireland. There is a sandstone in India 

 corresponding with the old red in England, occupying the 

 same relative position to the coal measures, and presenting 

 the same lithological characters, but how far its zoological con- 

 tents will be found to correspond with those of the English 



