250 Proceedings of the Royal Physical Society. 



irruption of a huge mass of granite, after the rocks had 

 received their present north-easterly strike, since there is no 

 distinct evidence of the main features of the strike having 

 been produced by this intrusion. The granite at some places 

 cuts right across the upturned edges of the Culm and Devonian 

 strata without producing any deviation in their trend. 



The granite of the Brocken was regarded as the founda- 

 tion of the geological series by the older geologists of the 

 Wernerian school. When Murchison first visited the Harz 

 in 1829 he was surprised to find, that instead of being the 

 oldest, the granite was the latest of the core rocks through 

 which it had been forced. He also subsequently reduced 

 the so-called " Transition series " of the Harz to order, show- 

 ing that much of the supposed very ancient greywacke was 

 of no greater antiquity than the Culm measures of Devon, 

 and that many of the slatey rocks belonged to the under- 

 lying formation which he had just named "Devonian." 



5. Denudation of the Ancient Harz. 



After the first upheaval, denudation began its work, and 

 the products of erosion were carried away and deposited 

 in the nearest sea bottom. Rolled pieces of the Hercynian 

 rocks are found in the Coal-measure and Permian deposits 

 on the flanks of the Harz, but why is granite, which has 

 such a prominent place among the rocks of the Harz, con- 

 spicuous by its absence from these deposits ? Was it per- 

 haps injected at a much later date than that of the deposi- 

 tion of the border rocks ? We shall see. The Upper Harz 

 metallic veins are in large fault fissures which were formed 

 after the rocks were folded. These veins run out to the 

 edge of the old formations, and disappear under the Zechstein 

 which rests unconformably on the core rocks, and also cuts 

 off the veins abruptly, showing that the fissures were formed 

 and subjected to atmospheric erosion before the Upper 

 Permian period. Quartz-porphyry dykes are known to run 

 through the core rocks in the neighbourhood of Lauterberg, 

 and are probably connected with the interbedded quartz- 

 porphyries of the Rothliegendes at that locality. They run 

 sometimes along fissures parallel to these just referred to. 



