246 Professor Sedgwick and Mr. Murchison on the 



refer to a section on the accompanying plate (PI. XXIII. fig. 7), as representing 

 one of the most illustrative of several traverses which we made, and in which the 

 order of the groups is apparent, notwithstanding the very complicated derange- 

 ments produced by the intrusive trappean masses. 



The physical features of this picturesque district are quite in harmony with the 

 varied condition of the component rocks ; each woody ridge being formed of the 

 harder plutonic and altered masses, while the valleys are excavated in the shale 

 and " schaalstein." 



The plutonic rocks consist of greenstone, both coarse and fine-grained, some examples of which have 

 a very thick-bedded, others an amorphous aspect. Some of the masses are porphyritic, while others 

 graduate into simple trappean " wacke," and amygdaloid, and resemble the " iosafte ew boules" of French 

 geologists, by decomposing into concentric crusts. Laumonite and other simple minerals are associated 

 with them. In one place the eruption of these masses has converted the sandstone into quartz rock; in 

 another the shale in contact is in the state of jasper. In some localities they are surmounted by peculiar 

 trappean conglomerates, in which organic remains are occasionally distinguishable, and they frequently 

 alternate with the " schaalstein," the peculiar bedded rock to which we have already adverted, and 

 which we will notice more at length when we describe the banks of the Lahn, where it is most developed. 



On the north side of the Leiterberg, near Eibach, the limestone and shale are 

 broken through, and thrown off both to the north and to the south ; and on the 

 south face of the hill, near its summit, the schists have been converted into a com- 

 plete jasper, which is surmounted by iron ores. The limestones are for the most 

 part in the state of " fluss-stein," avariety of altered rock in which the calcareous and 

 trappean or ferriferous matter are blended together, and which here (as also in the 

 environs of Oberscheld) contains beds abounding in fossils. The most prevalent 

 character, however, of the altered deposits of this district is the very general diffu- 

 sion of iron ore, which for the most part is in the state of brown oxide, and per- 

 vades the shale and limestone wherever they are in contact with the trap. 



Limestones of Oberscheld, Sessacher, 8fc. 



As the limestones of this tract of country contain several characteristic fossils 

 in common with the zone of Brilon, we can have no hesitation in considering them 

 of the true Devonian age. The matrix of the fossils is here also absolutely iden- 

 tical with that of Brilon ; in many places being so ferriferous that it passes into a 

 complete iron ore : in other places, where the calcareous matter prevails, it is used 

 as a flux for the ores, and hence its n^Lme fluss-stein. M. Beyrich has described this 

 rock as being uniformly overlaid by greenstone and supported by " schaalstein*." 



* M. Beyrich is we think in error in considering this limestone to be distinct from that of the Hand, 

 near Bensberg, before mentioned, and that of the Lahn which we shall presently describe. It is true 

 that the localities in which peculiar mineral conditions exist may contain some peculiar species of shells; 



