254 Proceedings of the Royal Physical Society. 



will be set free, and may, Tinder requisite conditions, be 

 precipitated as sulphides, oxides, or carbonates on the sea 

 floor. 



There is one contemporaneous metallic deposit still in 

 existence among the palseozoic rocks at the Eammelsberg. 

 It is also possible there may have been others now com- 

 pletely denuded away along with most of the Devonian 

 rocks of the Lower Harz, and the Kupferschiefer of Mansfeld 

 may perhaps be partly derived from their destruction. This 

 is only a suggestion to account for the richness of the deposit 

 at this locality. The seam extends over a very wide area, 

 but is not valuable enough to work on the western flank of 

 the Harz at Osterode, as it contains too little of the silver 

 from which the profits are made. It is also found along 

 the borders of the Thiiringer Wald under the same con- 

 ditions as on the Harz, so that over the great area between 

 the two mountain chains there must have been a large 

 inland basin in which deposition of fine sediment could go 

 on in uninterrupted tranquillity. 



7. Mesozoic Submergence. 



The Zechstein is separated geologically by a wide gulf 

 from the underlying Eothliegendes beds. The Upper Zech- 

 stein rocks bespeak a great change in the conditions of 

 deposition around the Harz. The land gradually sank and 

 became completely submerged, as no more pebbles of Palaeo- 

 zoic rocks are found in any of the overlying formations from 

 the Kupferschiefer upwards to the Chalk. 



The conditions during the Mesozoic ages appear to have 

 been generally tranquil in this region, and the various for- 

 mations to have been laid down in large open areas in which 

 marine forms could thrive and produce limestones and fossili- 

 ferous shales and marls without disturbance by upheavals or 

 volcanic eruptions. 



There can be little doubt that the Harz was covered by 

 the whole of the Secondary formations up to perhaps the 

 middle of the Cretaceous system, as these are found, both on 

 the northern and on the southern borders of the range. The 

 Cretaceous series, so abundant along the northern Harz border. 



