260 Professor Sedgwick and Mr. Murchison on the 



so very prevalent, that were he to depend upon that criterion alone as a proof of 

 superposition, he would infallibly be led to a conclusion respecting the thickness 

 of the whole series that would be utterly beyond belief. But in this way he would 

 be involved in a gross error ; for it has been shown that beds of limestone, schist 

 and sandstone, forming a peculiar mineral group, and having a peculiar group of 

 fossils, are (notwithstanding the prevailing south-eastern dip) repeated at certain 

 intervals along the supposed lines of section. 



Thus the Devonian rocks and some of the lowest members of the carboniferous 

 series, are (as we have already shown) clearly exposed near Dillenburg and Her- 

 born, amid many trappean eruptions and countless alternations of schaalsteins 

 or contemporaneous plutonic rocks (PI. XXIII. fig. 7). Continuing the section 

 southwards, the prevalent dip is still to the S.S.E., and yet rocks containing the 

 Pentamerus Knightii, and therefore most probably Silurian, are thrown up on one 

 point, overlaid again by the Devonian limestones of the Lahn, and containing the 

 same fossils which we find in the zones of Brilon and Dillenburg. 



Again, starting from the banks of the Lahn, where the limestones are in a state 

 of marble, charged with numerous unequivocal fossils identical with those of the 

 Westpbalian limestone, and loaded with pure Devonian species, the dip is still to 

 the S.S.E., an inclination w^iich is persistent throughout nearly the whole tract 

 extending to the foot of the Taunus. So that here again, if we trusted to vertical 

 sections, (in a country too where trap rocks, both contemporaneous and intru- 

 sive, are for ever protruding to the surface), we should necessarily arrive at the 

 conclusion, that the quartz rocks of the Taunus and the associated strata are not 

 of higher antiquity than the carboniferous epoch. The fossils, however, which we 

 collected in the slaty schists along the northern flanks of the Taunus, at Idstein, 

 Usingen, &c., contradict this conclusion; and the quartzose rocks of the Hunds- 

 riick (a continuation of the Taunus) afford, as we shall show., similar and still 

 more decisive evidence. These fossils are unquestionably of the same age as those 

 of some members of the older fossiliferous grauwacke in the regions above de- 

 scribed : and hence we are compelled to conclude, that many masses of the strata 

 between the Lahn and the Taunus are in an inverted position ; since the De- 

 vonian limestones, repeated in several parallels, seem to plunge under the Silurian 

 grauwacke*. 



* We are aware that M. Von Buch has long ago expressed his opinion that the Rhenish strata are not of 

 very high antiquity. Professor Noggerath's works are most full and instructive concerning the mineral com- 

 position of large portions of the country bordering on the Rhine, and they must always be referred to as 

 early and most important contributions towards a true knowledge of its physical structure. M. Steininger 

 must also be cited as having described some of the great calcareous masses we have called Devonian, 

 as forming a basin supported by the older grauwacke. We do not think it necessary here to advert to 



