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 containing 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 zechstein in Thu- 
ringia appear to be the equivalents of the Exeter 
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 hydrauhc 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. 
