162 



NEW RED SANDSTONE AND MARL. 



iron, and coloured red or yellow. The thickness of the beds differs 

 much in different situations, as might be expected from its lying upon 

 the lower beds unconformably, and therefore resting upon an uneven 

 surface. The lower new red sandstone in the western counties of 

 England, and in various parts of the Continent, contains fragments of 

 different rocks, cemented by ferruginous sand or marl, and masses 

 of imperfect porphyry, and abundance of felspar, both in a decompos- 

 ed state and in perfect crystals. The magnesian limestone, over the 

 lower red sandstone, should here be described in the ascending se- 

 ries ; but the description would disconnect the account of the upper 

 and lower red sandstone, which are strictly but one formation. I 

 shall, therefore, defer the description of the magnesian limestone, un- 

 til that of the red sandstone is gone through. In fact the magnesian 

 limestone does not always occur in the red sandstone. 



JVew Red Sandstone and Marl above magnesian limestone. The 

 beds have generally the prevailing colour which the name implies, 

 but are often marked with irregular veins and spots, of a yellowish or 

 bluish colour, and the sandstone is sometimes yellow or grey, with 

 occasional spots of red. 



The composition of different strata in this formation is extremely 

 various : in some parts, we find an argillaceous marl in different 

 states of induration, and, more or less, intermixed with calcareous 

 earth. In other parts, we meet with regular strata of siliceous sand- 

 stone ; and sometimes, we have a conglomerate sandstone, or a soft 

 sandstone, enclosing rounded pebbles of quartz and Lydran stone, 

 granite and porphyry, as in the rock on which Nottingham and the 

 Castle stand. In the lower part of this division, as well as in that 

 beneath the magnesian limestone, the beds are porphyritic, and con- 

 tain imperfect crystals of felspar; sometimes, they pass into amyg- 

 daloid and trap. The fine siliceous sandstones, when closely exam- 

 ined, are often found to conta-in fragments of the neighbouring rocks : 

 thus, the sandstone in the vicinity of Charnwood Forest, as before 

 slated, contains fragments of slate and chlorite slate ; and the con- 

 glomerate beds on the northern side of that range of hills, are com- 

 posed principally of fragments of granitic and slate rocks. No for- 

 mation presents such a great variety of mineral characters as the red 

 marl and sandstone. In England, it has frequently been confound- 

 ed with the red sandstone and conglomerate, that occur under the up- 

 per transition limestone, called by English geologists the old red sand- 

 stone. Bui the old red sandstone of foreign geologists, or rotke-todie- 

 liegende,^ the gres ancien of Daubuisson, covers the coal formation, 

 and therefore corresponds with the lowest beds of the English red 

 marl and sandstone. 



* The name Rothe-todte-liegende, or red dead lier, was first applied to what the 

 English call the old red sandstone, below the coal formation, because no coal wao 

 found under it. 



