260 Proceedings of the Royal Physical Society. 



sea-level till tlie end of the Senonian period, when the whole 

 sea floor was laid bare, and all further deposition arrested. 



There appears to be no evidence of post-cretaceous sub- 

 mergence in this district, and it is difi&cult to determine the 

 date at which the upheaval ceased. The most important re- 

 presentative of the Tertiary deposits is the Oligocene Brown 

 Coal which occurs in depressions at various places on and 

 around the Harz. A bed of workable brown coal, 50 feet in 

 thickness, occupies a bay-like hollow in the core rocks im- 

 mediately adjoining the line of fault at Wienrode between 

 Thale and Blankenburg. The coal appears to cross the line 

 of dislocation, and rest on the upturned edges of the Zech- 

 stein and Eed Bunter sandstone in a way which seems 

 clearly to show that the upward movement had entirely 

 ceased before the agencies of denudation had hollowed out 

 the depression subsequently filled up by the vegetable 

 deposit. 



10. Eecapitulation. 



The area now occupied by the Harz Mountains was, during 

 the Palaeozoic period, a portion of the great sea in which the 

 Silurian, Devonian, and Lower Carboniferous rocks of Central 

 Europe were deposited. The alternating greywackes, sand- 

 stones, shales, and limestones, with their accompanying 

 fossils, indicate changes in the depth and condition of the 

 water, but form throughout a perfectly conformable series. 

 Volcanic action was vigorous in the Devonian period, when 

 diabases and tuffs were emitted at various parts of the area. 



Towards the close of the Lower Carboniferous period the 

 sea shallowed, and deposition was finally arrested by the 

 upheaval of the new-made rocks which were thrown into a 

 series of violent folds, with a general N.E. and S.W. trend. 

 The folding was followed by the irruption of great bosses of 

 granite, after which the region was dislocated by a series of 

 powerful faults which produced the fissures now filled by 

 the metallic veins of the Upper Harz. The faulting took 

 place at the time of the Upper Coal Measures, and the up- 

 heaved area remained exposed to subaerial denudation 

 throughout the remainder of the Carboniferous period. The 



