424 Geological Society. 



In following out these strata to the E.N.E, the authors were 

 astonished at the vast flexures, first laid down by Von Buch and 

 Hoffman, and since more elaborately made out by Von Dechen and 

 Erbreich ; and perceived that the shales become more crystalline and 

 slaty, and charged with mineral veins, and the limestones assume 

 the state of marble or highly ferriferous rocks ; these strata are also 

 abundantly interrupted by ridges of Trap and frequently inverted, 

 the carboniferous and Devonian deposits plunging under the older 

 Grauwacke or Silurian rocks. 



Our authors also found that the Devonian strata reappeared in 

 irregular troughs among the Silurian Grauwacke (often with in- 

 verted inclination) in various parts of Nassau ; many of the lime- 

 stones, particularly on the river Lahn, being identical, both in 

 structure and in coralline remains, with the beautiful marbles of 

 Babbacombe, Torquay, and Plymouth. In many parts of this re- 

 gion the strata are in a highly mineralized condition, copper and 

 lead ores, as well as the more prevalent iron mines, occurring at 

 intervals ; whilst numberless eruptive rocks divei'sify the surface ; 

 and the strata, particularly those of the Devonian age, alternate 

 with a peculiar stratified contemporaneous trap-rock called " Schaal- 

 stein," the more schistose varieties of which contain Devonian fossils. 

 The various mineral waters of Nassau are supposed to be due to the 

 last expiring effects of the same causes which produced, in former 

 times, the numerous eruptions of Greenstone, Porphyry, and other 

 igneous rocks. 



The quartz rock of the Taunus mountains, the southern limit of 

 the region they examined, is considered to be an altered deposit of 

 the Silurian epoch*. 



ous band (defining the same as berg-kalk) , the limestone which at Ra- 

 tingen is undoubtedly true mountain -Hmestone, and the calcareous zone 

 which passes from W.S.W. to E.N.E. by the towns of Elberfeldt and 

 Iserlohn. Now although at a first glance the physical features of the 

 country seemed to favour this view (which was indeed adopted in the new 

 map of Von Dechen), the close examination of the authors detected, that 

 whilst the Ratingen limestone contained the fossils of the carboniferous 

 system, that of Elberfeldt and Iserlohn was charged with dift'erent types, 

 most of which exist in the lower limestone of Devonshire. Having assured 

 themselves, therefore, that there was an error in the works of previous 

 observers, they returned to Ratingen, and following the carboniferous 

 limestone eastward along its strike they found it to be separated from 

 that of Elberfeldt, gradually changing in its structure, and passing into 

 thin-bedded black limestone associated with much flinty schist (kiescl 

 schiefer) and chert, and assuming the lithological characters and fossils of 

 the black or culm-limestone of Devonshire. 



This black limestone is overlaid by unproductive measures of the coal 

 series, similar to the upper strata of the great trough of North Devon, and 

 is underlaid by psammites, schists, and limestone (Elberfeldt and Iser- 

 lohn) containing Devonian fossils, and reposing upon schistose and grau- 

 wacke rocks which contain Silurian fossils. 



* The most characteristic Devonian Mollusca are Strygoccphalus, Gypi- 

 dium, two or three species of Turritella, Euoraphalus, the Tcrebratula of 



