S26 M. DE BoNNARD OTl the 



sometimes limited to the mountains which immediately 

 coiifine the bed of the river. This trappean zone is also 

 prolonged on the S.W. into the basin of the Brems, but in a 

 less continuous manner than on the banks of the Nahe. 



On the left bank of the latter river, the trap suddenly 

 and completely disappears on arriving at the schistose forma- 

 tions : this limit oflfers very interesting geological points of 

 view, from the different aspect presented by the mountains 

 of the two formations. The soil of the Hunsdruck is gene- 

 rally of a greyish tint ; vast and level platforms are there ob- 

 served, with scattered blocks of white quartz, in general 

 well cultivated, though not fertile, and covered with fine 

 forests of beech and oak. These platforms are furrowed by 

 valleys with steep sides, but uniform and generally covered 

 with vegetable soil. On the trap formation, a reddish brown 

 soil is seen, of nearly general barrenness, and scarcely 

 wooded ; the summits of the mountains present rounded 

 hummocks, but their sides are broken and expose numerous 

 escarpments of blackish rocks. Vast excavations cut on the 

 surface for the extraction of the iron ores, almost exactly mark 

 the limits of the two formations. On the right bank of the 

 Nahe, on the contrary, the trap is found in the midst of the 

 coal measures of the Palatinate, as far as eigiit or ten leagues 

 from the river, forming either isolated hills, or branches of 

 mountains less elevated than the principal chain, but gene- 

 rally directed like it from S.W. to N.E. This trap forma- 

 tion is principally composed of corneans,* wackes, green- 

 stones, and amygdaloids (the latter rock contains agates, 

 chabasites, prehnites, &c. in the environs of Oberstein). 

 Sometimes the cornean passes into flinty slate (kieselschiefer) 

 well characterized, and of a black colour ; but it also passes 

 into a basalt, and all the rocks become entirely analogous to 

 basaltic rocks. In some localities, particularly near St. 

 Wendel, and in the valley of Oberwiesen, on the north of 



* I have adopted the word " Cornean " as a translation of the French 

 " Corneanne." In a paper on Southern Pembrokeshire, lately sent to 

 the Geological Society, I have had frequent occasion to mention this 

 kind of rock; the reasons for adopting the word Cornean are there 

 stated. (Trans.) 



