NEW RED SANDSTONE. 161 



New Red Sandstone is so called to distinguish it from a red sand- 

 stone found among transition rocks, (See Chap. VII.) The new red 

 sandstone is a very extensive and complex formation : its prevailing 

 mineral character is siliceous ; but it sometimes comprises calcareous 

 beds of considerable magnitude and extent. The new red sandstone 

 may be conveniently divided into three series, or the upper, the mid- 

 dle, and the lower beds ; where the beds of limestone occur, they 

 serve to mark the divisions in the series with sufficient distinctness, 

 but where they are wanting, these divisions cannot always be observ- 

 ed. A limestone containing magnesia, separates the lower from the 

 middle series, in the northern counties of England, but is wanting in 

 the midland and western counties. 



In France, a calcareous bed, called muschel-kalk, separates the 

 middle series from the upper; but this has not been discovered in 

 England. The red sandstone in England covers the lower rocks un- 

 conformably, which proves that the lower rocks were tilled up, be- 

 fore the strata of red sandstone here were deposited : this upheaving 

 of the lower beds must have been attended with great convulsions, 

 which probably supplied the sand and fragments, of which many of 

 the beds of red sandstone are composed. Indeed, it is highly prob- 

 able, that this sandstone, and the conglomerate beds in different parts 

 of it, were formed by the violent disintegration of the older rocks, 

 and of trap rocks, that were protruded at the era of some great con- 

 vulsion, which broke down a large portion of the ancient crust of the 

 globe, and spread the debris, far and wide, over the bed of the ex- 

 isting ocean. Fragments of the older rocks occur in the different 

 beds of this sandstone, and some of the beds are formed almost en- 

 tirely of such fragments. This mode of formation, would sufficient- 

 - ly account for the great diversity, both in the nature and thickness of 

 the beds, in different districts. I am inclined to believe, that the dis- 

 integrating causes which broke down part of the ancient rocks, and 

 spread their ruins over a great extent of surface, acted at successive 

 periods of comparatively short duration, succeeded by long intervals 

 of repose, during which the calcareous strata were deposited. 



The lower red sandstone was not known as a member of the red 

 sandstone formation in England, before Professor Sedgwick ascer- 

 tained, that it formed beds of considerable magnitude below the mag- 

 nesian limestone in Durham and Yorkshire. It does not, however, 

 extend, as he supposed, to the southern termination of the magne- 

 sian limestone in Nottinghamshire ; for there I have found the lowest 

 beds of magnesian limestone resting immediately on the coal meas- 

 ures, and a part of the upper red sandstone covering the limestone. 

 The lowest beds of red sandstone are, in some situations, conglom- 

 erates ; in others coarse, siliceous sandstone is often much intermix- 

 ed with decomposing crystals of felspar. Sometimes, it is found 

 finer grained, and mixed with micaceous shale and reddish marl. 

 The beds are, generally, more or less impregnated with the oxyd of 



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