236 Proceedings of the Royal Physical Society. 



adinoles at Lerbach occur between the Kieselschiefer in close 

 proximity to the contemporaneous diabase and tuff beds in- 

 tercalated with the Devonian and Culm at that locality. 



(2.) The other facies of contact metamorphism is developed 

 chiefly to the north of the central axis, while the variety just 

 described occurs on the opposite side. It is characteristically 

 developed on the river Lupbode below AUrode, and on the 

 Eapbode between Eiibeland and Hasselfelde, where the 

 diabases are girdled by zones of " Spilosit " and *' Desmosit." 

 The former is a finely foliated schist with small spots of 

 darker colour and undefined edges. The latter, instead of 

 being spotted, has a banded structure, but is essentially the 

 same rock. 



The sedimentary rocks surrounding the granitic masses 

 are much more highly metamorphosed. They are converted 

 into hornfels — a comprehensive term, including a variety of 

 rocks which have been hardened and altered into a tough 

 horny mass. Heated water in trying to escape from before 

 the rising mass of molten rock below, appears to have played 

 an important part in the alteration of the sedimentary strata. 

 The greywackes and clayslates contain an abnormal quantity 

 of silica, and many foreign minerals, including garnets, 

 actinolite, cordierite, mica, vesuvianite, and tourmaline, 

 have, by the same agency, been formed in the altered rock. 

 A schistose or gneissic structure is sometimes to be found 

 close to the edge of the granite where metamorphism has 

 been greatest. 



h. Regional Metamorphism. 



The Hercynian rocks, particularly those of the Wieder- 

 schiefer zone, have undergone a certain amount of regional 

 metamorphism between the granite masses of the Brocken 

 and Kamberg ; and the Lower Devonian along a line running 

 S.W. from the neighbourhood of Hettstedt, and parallel to 

 the boundary of the Palaeozoic series. 



The metamorphism has, according to Lossen, been propor- 

 tional to the amount of folding and contortion the strata have 

 undergone. Between the granite masses a peculiar rock 

 named Porjphyroid is developed in considerable quantity. It 



