442 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 4, 



vonian, are in one spot (as at Lauthenthal) in the form of flinty 

 slates (Kiesel-schiefer) and Posidonomya schists (fig. 7, e, /, g), 

 while in another locality distant only four or five English miles, 

 they are limestones charged with numerous Producti and fossils of 

 the Mountain Limestone (fig. 8, c, d, e). 



In its partial appearance and disappearance within very short 

 distances, and in its passage into flinty schist and Posidonomya shale, 

 the Carboniferous Limestone of the Western Harz entirely resembles 

 the rock of the same age in Westphalia, as described by one of us 

 and his companion, and those of the Thiiringerwald and Saxony. In 

 no other part of this region, except near Grund, is there any band 

 of Carboniferous limestone like that in question. But its associates 

 and equivalents occur in very many spots, and specially near Clausthal, 

 where some of the richest veins of true argentiferous galena traverse 

 the strata containing the Posidonomya Becheri, with occasional hard 

 flinty slate. 



These Posidonomya strata, often of very considerable dimensions, 

 and inclined in every direction from verticality to a slight deviation 

 from horizontality, are succeeded upwards by other sandstones and 

 schists, which we considered to be of the same age as the Millstone- 

 grit and Culm deposits of England. Occasionally there are to be 

 seen great masses of thick-bedded sandstone of lightish colours, 

 which were described as having subordinate layers of micaceous flag- 

 stone and dark carbonaceous shale, as well as beds of a very coarse 

 grit, with granules of greasy quartz as large as peas, like some 

 varieties of the millstone grit of Britain. 



The greater and uppermost mass of all this series was said to consist 

 of dark shale and schist, with very thin-bedded hard sandstone, con- 

 taining reed-like and grassy small plants ; and this was first compared 

 by Sedgwick and Murchison with the Culm fields of Devonshire. 



It would appear that subsequent researches (even to the year 

 1854 inclusive) have confirmed these early comparisons. Besides the 

 labours of M. Adolf Roemer near Clausthal, where the dislocations 

 are so great as to render it almost hopeless to trace any order, except 

 through the discovery of fossils, we again call attention to the me- 

 moir of M. Carl Prediger, who seems to have met with some physical 

 proofs of succession to the south of Andreasberg. The " altere 

 ^M^m-grauwacke " of this author is the band which was formerly 

 shown by English geologists to be the equivalent of the Carboniferous 

 Limestone and Posidonomya shale ; this " -ff'?/^w2-sandstein " (which 

 in the long ridge of the Bruch Berg becomes, as in the Taunus, a 

 sort of quartz rock) is that which they paralleled vnth. the Millstone- 

 grit ; and his " obere Kulm-grsmwacke " is the Culm-field proper of 

 North Devon, as long ago indicated *. 



* We are the more particular in referring the reader to the original compari- 

 son by Sedgwick and Murchison whereby these rocks were first paralleled with 

 the Culm series of the S.W. of England, because modern German writers, like 

 M. Prediger, seem to ignore the fact. M. Prediger refers to M. Adolf Roemer 

 as the author of a comparison which is, we believe, exclusively that of the English 

 explorers of 1839. See Trans. Geol. Soc. Lond. 2 ser. vol. vi. (Section from 

 Osterode to Clausthal) p. 288. 



