46 Murchisoris Silurian System. 



With regard to the purely scientific part of the de- 

 tails given by Mr. Murchison on the subject of the New 

 Red Sandstone, that author observes, that his inquiries may 



" lead geologists to modify their previous theoretical views respecting 

 the relations of the coal measures to the overlying rocks, founded on 

 what must now be considered local phenomena, observed chiefly in the 

 Bristol district and south-western parts of England ; where because 

 the New Red Sandstone reposes unconformably upon the carboniferous 

 strata the belief became prevalent, that this arrangement was indicative 

 of a general rupture, subsequent to the accumulation of the coal mea- 

 sures, and anterior to the deposition of the magnesian limestone and 

 conglomerate. That such, however, has not been generally the case, 

 has been established with regard to the north of England, by the 

 writings of Professor Sedgwick; and the preceding facts teach us the 

 same lesson in respect to the central counties : for it is clearly demon- 

 strated, that beds of the age of the dolomitic conglomerate are there 

 separated from those of the carboniferous system by an unbroken suc- 

 cession of intermediate strata of vast thickness, of which there are few 

 or no traces in the south-western parts of the island. 



" Notwithstanding, however, the distinctions which have been drawn 

 between the different members of the New Red System in the central 

 counties, a question it is feared might still arise among foreign readers, 

 concerning the true equivalent of the Rothe-todte-liegende : for as most 

 continental geologists conceive that formation to be essentially connect- 

 ed with porphyritic and other rocks of igneous origin, they can scarcely 

 peruse the description of the trappean conglomerate without supposing 

 that those masses may represent the German deposit. If, however, we 

 are to understand the foreign synonym to express a series of strata, 

 elaborated in such a manner, as in some cases completely to connect 

 the carboniferous and overlying system ; then it is clear we must consi- 

 der the Lower New Red Sandstone to be its true and full equivalent, 

 even should it not contain a single pebble of trap. That it contains few 

 or no fragments of trap in the north of England, has already been prov- 

 ed by Professor Sedgwick, and the same fact is now established in the 

 central counties. Whilst, on the other hand, the great trappean conglo- 

 merates have been shown to overlie this equivalent of the Rothe- 

 todte-liegende, and to be on the same parallel with the dolomitic conglo- 

 merate. Referring to former opinions on this point, Professor Sedgwick 

 has well observed, "In comparing the Bristol and Exeter conglomerates 



