560 



THE WONDERS OF GEOLOGY. Lect. V. 



the Lower New Red, or Magnesian limestone formation ; 

 it comprises the Zechstein and Rothliegende of the Germans, 

 and all the deposits that intervene between the lowermost 

 bed of the Trias and the Carboniferous system. Like 

 the upper series, it consists of marls, clays, and conglo- 

 merates, more or less coloured by hydrates and oxides of 

 iron, pyritous shales, gypsum, &c. It comprises strata 

 of great extent and thickness, of limestone containing a 

 large proportion of magnesia, and of a crystalline calcareo- 

 magnesian stone, termed Dolomite.* I have already men- 

 tioned that this system is paleontologically characterized 

 by a peculiar type of organic remains, and by the absence 

 of every species of fossil that occurs in the newer, or 

 overlying formations ; hence the Permian is ranked as the 

 last, or uppermost, of the palaeozoic class. (See Synopsis, 

 p. 203.)f 



In Somersetshire, and the adjacent country around 

 Bristol, beds of conglomerate, formed of the debris of 

 older rocks, held together by a dolomitic cement, are 

 spread unconformably over the carboniferous strata, filling 

 up the irregularities and hollows of the surface of the 

 mountain limestone, &c. occasioned by the dislocations and 

 fractures which those rocks had sustained by disturbing 

 forces, before the deposition of the Permian deposits. This 



* The granular crystalline magnesian limestone is termed Dolo- 

 mite, from M. Dolomieu, who first pointed out its mineral ogical 

 character. This rock has the same external aspect as granular lime- 

 stone ; but, instead of being a pure carbonate of lime, contains from 

 45 to 60 per cent, of carbonate of magnesia. 



f The arrangement adopted in the text is that now generally 

 received by British geologists ; at the same time it must be stated, 

 that very able observers limit the term " palaeozoic" to the forma- 

 tions below the carboniferous system, and rank the Permian with the 

 mesozoic. or middle secondary strata. Sec a Paper on the " Termi- 

 nation of the Palaeozoic Period," by Dr. Dale Owen, " American Journal 

 of Science," for May, 1847, vol. Hi. New Series, p. 305. 



