older Deposits of the North of Germany and Belgium. 231 



5. Sandy and slightly micaceous shales passing into flagstone. 



6. Thin course of dark grey or black limestone. 



7. Shale. 



The descending section at this spot is not further continuous, being interrupted 

 by a depression and water-course ; but as other limestones of very dark colour and 

 considerable thickness rise up and occupy the northern sides of the low hills be- 

 tween Cromford and Ratingen, they must be considered as lower strata of the same 

 formation, to which they are, indeed, allied, by containing some fossils which occur 

 in the upper beds. 



In tracing this band of limestone to the E.N.E., we find it well laid open 

 beneath the incumbent drift, in the great quarries of Brock-haus, about three 

 miles from Cromford, where the surface of the limestone gives still more striking 

 proofs of having been subjected to great violence, and is covered with much de- 

 tritus. Near Isambiigel the limestone begins to rise into higher ground, and to 

 occupy the surface of the country, being exposed in various quarries along the 

 sides of longitudinal ravines, by which we are enabled to trace the connexion of the 

 rock with the overlying beds, or lower members of the coal-field. The upper beds 

 of the limestone pass into, and are intimately associated with, dark, flat-bedded, 

 flinty slate, which in parts is undistinguishable from the black cherts of our 

 mountain limestone. The mass is overlaid by shale and psammite ; and these 

 again by other shale beds, in which occur still thinner courses of black flinty slate, 

 &c. The whole of these beds dip under the great series of shale, psammite, and 

 quartzose sandstone, which we have previously mentioned as forming the base of 

 the coal-field. 



Farther on its strike the carboniferous limestone assumes a still more cherty 

 character ; and in the woody hills near Velbert the prominent feature of the for- 

 mation is the prevalence of chert, charged with impressions and casts of large 

 Encrinites, so as to be undistinguishable from the Derbyshire '' screwstone." Here 

 also we have a distinct proof that the limestone and " kiesel schiefer " dip under the 

 black pyritous shale or " alaun schiefer" of the neighbourhood (see PI. XXIII. 

 Section fig. 2). 



In following the calcareous bands into the valley of Regrath beyond Velbert, 

 we perceive that they still more change their lithological aspect ; becoming hard 

 and black, and exhibiting none of those fine masses of light-coloured limestone 

 and that profusion of fossils which we observed at Cromford, near Ratingen. The 

 limestone, on the contrary, juts out here and there in irregular hummocks, often 

 in vertical positions and with imperfect traces of stratification ; or is bent into 

 segments of circles, and is much altered in structure, partly from the effect of 

 violent dislocations. 



2 H 2 



