280 Professor Sedgwick and Mr. Murchison on the 



Rhine, is still further maintained by the numerous obscure vegetable impressions 

 which are found in both of them ; very seldom, however, in such a state as to give 

 any hopes of determining their species. 



Older Slates of the Moselle and the Rhine. — Formations of the Hundsriick and the 

 Taunus, &;c. (Map, PI. XXIV. colour 8, PI. XXIII. Sect. 9, colour i.) 



We twice crossed the ridge between the north-eastern limits of the Eifel and the 

 gorges of the Ahr, and we made three or four distinct traverses from the south- 

 eastern ridges of the Eifel to the basin of the Moselle. From the Moselle we made 

 traverses across the Hundsriick ; and we endeavoured to connect our work together 

 by an examination of the old rocks on the banks of the Moselle, and by repeated 

 examinations of all the older rocks in the gorges of the Rhine between Bonn and 

 Bingen. As a general result of these examinations, we may state, that we were 

 not able, by any direct evidence of sections, to establish the order of superposition 

 between the Eifel and the Hundsriick ; in which respect we, however, encountered 

 no greater difficulties than we had met with in the Ardennes and on the right 

 bank of the Rhine. But in course of these traverses we found a series of great 

 mineral masses following one another nearly in the order we have already de- 

 scribed. 



Under the great fossiliferous group containing the red shales and psamraites is an enormous develop- 

 ment of slaty flagstones, earthy schist, and shale of yellowish-grey, greenish-grey, and bluish-grey 

 colours ; sometimes blending themselves in structure with the upper group ; sometimes passing into the 

 condition of a coarse slate formation like the upper slates of the Ardennes, — not unusually presenting 

 vegetable impressions, and occasionally bands marked with innumerable impressions of Encrinites, Corals, 

 Orthidea, &c. 



With these characters they appear in the gorges of the Lieser between Bleckhausen and Mander- 

 scheid, often in vertical positions, or thrown into the most fantastical contortions, — in the gorges that de- 

 scend toward the Moselle, between Daun and Lutzerath, — in the magnificent sections of the Ahr — and on 

 both banks of the Rhine between Bonn and Andernach. Similar rocks, and with the same general suite 

 of fossils, follow both banks of the Rhine above Coblentz ; and near the mouth of the Lahn they are 

 shown to plunge under the limestones of the Devonian system described in the former part of this 

 paper. 



Ln the escarpments near Braubach and the mouth of the Lahn these rocks are, as already stated, ex- 

 tremely fossiliferous; the long-winged Delthyris {Spirifer, Goldfuss) and the Homalonoti being abun- 

 dant, and the whole suite agreeing with that which we have already described, and considered as cha- 

 racteristic of the Silurian system in the Rhenish provinces. 



Near Boppart, south of the mouth of the Lahn, the mineral system of the Rhine changes its character ; 

 not by any sudden transition nor in any well-marked order of superposition, but among numberless 

 contortions, and by insensible gradations ; so that above Oberwesel the whole has more the character 

 of a slate formation than of an arenaceous flagstone. Beds of quartzite alternate, here and there, with 

 fine masses of roofing-slate, which is obtained by a true transverse cleavage ; and on both banks of the 



