304 M. D'Omalius D'Halloy on a 



The rocks classed in this secondary group do not, by them- 

 selves, form extensive countries ; but they often appear in 

 those countries where the primordial rocks predominate, 

 principally in those of granite. At other times they shew 

 themselves in the lower parts of masses covered by newer 

 rocks : so that, with respect to the space occupied on the 

 map, I should have united it to other formations, if their 

 geological importance and distinctive characters did not for- 

 bid such an association. 



I unite many systems of rocks to form the second group, 

 the most important are known by the name of Zechstein, or 

 older Alpine limestone,* variegated sandstone,! muschel- 

 kalk, qaadersandstein, and jura limestone. J 



These rocks are often very distinct, but some possess com- 

 mon relations, which justify the approximation that their 

 geographical situation in France has allowed me to make. 

 They are so intimately united with those of the preceding 

 group, that it is very difficult to establish the line of separa- 

 tion. I even consider that if my work had been more es- 

 pecially applied to Germany, instead of France, it would 

 have been better to arrange the two first systems in the pre- 

 ceding group ; for zechstein often occurs subordinate to the 

 red sandstone, and the variegated sandstone constitutes 

 regions which very much resemble those in which the red 

 sandstone predominates. 



But on the other hand, the zechstein occurs in the Alps, the 

 Cevennes, and the Pyrenees, with characters that so much 

 approximate it to muschelkalk and jura limestone, that it 

 appeared to me preferable to group it provisionally with 

 those rocks, the more so as the materials I possess on France, 

 would not have afforded me the means of keeping up the 

 distinction throughout the mass. I moreover consider that 

 the zechstein is rare in the part of France to the north of the 

 Alps and the Cevennes, that a trace of it only exists there, 



• Magnesian limestone. (Trans.) 



+ New red or saliferous sandstone. (Trans.) 



J Oolite formation. 



