234 Professor Sedgwick and Mr. Murchison on the 



We found also in the black, flat-bedded limestones a small Trilobite, which we consider to be a true moun- 

 tain limestone species : and these fossils are associated with the Posidonia so characteristic of the culm 

 limestone of Devonshire. All these facts offer strong presumptive evidence in favour of the correctness 

 of our views. 



In following this zone upon its outcrop into the eastern districts of Westphalia, 

 we find it bending with the enormous flexures of the inferior strata, and projecting 

 at an acute angle to Arnsberg; whence it is suddenly deflected to the south-west, 

 exhibiting all the contortions and undulations dependent upon such a vast curvature 

 of the line of bearing (see map 6 + and woodcut, fig. l.p. 233). After turning, with a 

 south-western strike, to a point several miles south of Langscheid, it is again (along 

 with all the neighbouring formations) bent back at an acute angle, into its former 

 bearing, and is thence prolonged into the country near Brilon. In this part of 

 its range it partakes of all the accidents of the neighbouring formations, and passes 

 through a district so enormously convulsed, that all the strata through extensive 

 tracts of country are absolutely inverted ; yet does it continue to occupy its true re- 

 lative place on the surface, between the mountainous regions of the older formations 

 and the secondary deposits of the low country to the north. Continuing its range, 

 sometimes with, sometimes without limestone, but always characterized by its 

 courses of flinty slate (" kiesel schiefer ") and its schists with Posidonia^, it wraps 

 round the north-eastern extremity of the chain of older rocks by Bleuwashe, Stadt- 

 berg and Marsberg, and is again exhibited in another parallel zone which is pro- 

 longed towards Attendorn. 



Trusting to the labours of our German friends (and particularly to those of M. 

 Von Dechen and M. Erbreich, who have constructed the geological map of this re- 

 gion), we have laid down the same rocks, as repeated in two parallel troughs, sur- 

 rounded by the older strata, in a tract south-east of Berlenburg. 



From our own observations we are also led to identify with the same group some of 

 the uppermost strata of the environs of Dillenburg ; namely, those of Herborn and its 

 immediate vicinity (figs. 7, 8, of Sections, and colours 6^ and 6+ of Map), where Po- 

 sidonia schists, " kiesel schiefer," and bands of black limestone with Goniatites, are 

 abundant. We defer, however, for a few pages our account of the comphcated relations 

 of this tract of country, inasmuch as the sections it exhibits are incomplete in the as- 

 cending order, and the beds are minerahzed and changed by contemporaneous, as 

 well as intrusive, trappean rocks. We first endeavour to ascertain the characters and 

 sequence of the successive formations in the country bordering on the great coal- 

 field, where the ascending sections are complete and the beds much less disturbed ; 

 and availing ourselves of this sequence, we then attempt to explain the more 

 difficult relations of tracts of country (such as Dillenburg), where the same for- 

 mations are repeated through the efiects of those great undulations, to which we 



