1855.J MURCHISON AND MORRIS— THURINGERWALD, ETC. 449 



phical direction of the masses of rock, from their normal aUnement of 

 N.E. & S.W. to one trending from N.W. to S.E.; the turbulence of 

 the period being decisively characterized by great outbursts of por- 

 phyry and the extravasation of vast sheets of porphyritic lava. 



It is, indeed, manifest from the convoluted and dislocated condition 

 of the secondary strata, particularly those of the Muschelkalk, which 

 lie between the Thiiringerwald and the Harz, as well as from similar 

 appearances extending even to the older tertiary rocks lying north of 

 the Harz, or between that ridge and the line of ancient rocks near 

 Magdeburg, that each of the elder or flanking masses was an habitual 

 area of upheaval and oscillation, the upward and downward move- 

 ments of which compressed the interjacent formations into the pli- 

 cated forms which they still exhibit. 



In reflecting upon the broad external features only which were 

 successively impressed on the one tract and on the other, we infer, 

 that, however the two regions were thrown into nearly parallel direc- 

 tions, there are in the Thuringerwald proofs of ancient movements of 

 which we find no trace in the Harz. In this way we obtain evidence 

 of the truly local character of all such disruptions, in addition to the 

 examples previously cited by one of us, and to other cases mentioned 

 by M. Barrande*. 



In truth, whilst each of the tracts here spoken of present some 

 marked analogies to the Silurian basin of Bohemia, each of them 

 differs more from that tract than they do from one another. In their 

 great fundamental rocks of greenish and talcose grauwacke, the South 

 Thuringerwald and the district of Prague are alike, as well as in the 

 chief mass of the Lower Silurian rocks, though the fossils of the 

 primordial zone of Bohemia have not been found in the Thiiringer- 

 wald, and all the Lower Silurian is wanting in the Harz. 



Again, the rich Upper Silurian limestones of Bohemia have no true 

 representatives in Thuringia, — the uppermost member only of that 

 division having been detected in the Harz. 



Still more striking is the distinction between the two tracts under 

 consideration and the basin of Bohemia ; for whilst the Harz con- 

 tains all the members of the Devonian rocks, with a copious develop- 

 ment of the Lower Carboniferous, and whilst the Thiiringerwald 

 differs from it in not possessing either the central or the lower De- 

 vonian bands, there are no evidences of the existence of these forma- 

 tions in Bohemia, where the Silurian rocks are at once and abruptly 

 followed by the Upper Coal-fields. 



We collate these data to show, that whilst there are breaks in the 

 Silurian series of Britain, — ex. gr. in one part of S. Wales beneath 

 the Wenlock Shale, and* above the Upper Caradoc or May Hill sand- 

 stone, and in another below the latter rock, — that in the north of 

 England the Devonian rocks consist of a mere conglomerate, and that 

 even one part of the south-west coal field is known to be transgressive 

 to another, — our country offers no example of that great fracture 

 between the lower and upper divisions of the Carboniferous group 

 which is so very dominant a physical feature throughout Germany 

 and France. 



* See Bull. Soe. Geol. France, vol. xi. p. 311, &c. 



