96 



UPPER SECONDARY ROCKS. 



A writer in the 7th vol. of the American Quar- 

 terly Review thus characterizes the supermedial or 

 secondary order of rocks. " It consists of several 

 formations, each of them contain^ing alternating beds 

 of limestone, sandstone, and clay, and each having 

 fossils peculiar to its several floors. The lower beds 

 of this order contain rock-salt and salt-brine, togeth- 

 er with gypsum. These minerals lie in what is call- 

 ed the new red sandstone formation, which resem- 

 bles the old red sandstone so closely sometimes 

 that it is not easily distinguished from it. The mid- 

 dle beds consist of magnesian limestone in England; 

 in Germany they are called zechstein, and rest upon 

 a schist containing copper. It is called copper-slate, 

 and contains fossil fish, plants, and the monitor. 

 The beds which lie between the zechslein in Thu- 

 ringia appear to be the equivalents of the Exetei 

 conglomerate, which in many instances shows a de- 

 cided trap origin. Indeed, we have reasons for sup- 

 posing many red earths of this character to be de- 

 composed greenstones. With the termination of 

 the coal measures, a new order of things begins. 

 The disturbing causes which have hitherto disloca- 

 ted the beds, and thrown them often into high incli- 

 nations, seem to have ceased ; and the rocks hence- 

 forward conform to a general horizontality. The 

 beds of the lias, one of the most interesting forma- 

 tions, appear to have been deposited at periods of 

 great repose. 



" The lower ones consist of thin argillaceous lime- 

 stones, separated by marly partings ; the upper beds, 

 which are more than twice as thick, consist of blue 

 marls, indurated marls, and irregular limestones. 

 Some of these are fibrous ; and the septaria, or ce- 

 ment stones, are used for hydraulic mortar." 



In general, the upper secondary rocks differ from 



It must be borne in mind, however, that in all hilly and mount- 

 ainous countries particularly, the strata are more or less incli- 

 ned, overlapping each other. 



