114 



The compact serpentines stand in the closest relation to the schistose 

 variety already described. They consist mainly of aiitigorite scales ; and 

 very commonly these scales are seen to be arranged in two sets of parallel 

 planes meeting at an angle of about 90, thus producing a netting-like 

 (gestrickte) structure. This netting-like arrangement comes out strongly 

 between crossed nicols. The centres of the meshes are sometimes occupied 

 by salite-grains, many of which give simultaneous extinction. In short the 

 salite-grains are related to the antigorite-serpeiitine exactly as the olivine- 

 grains to normal serpentine, and the hornblende- grains to the serpentine with 

 lattice-structure. Diallage and staurolite were not observed in the massive 

 serpentine ; and chlorite and talc were less common than in the schistose 

 rock. 



The following bulk-analyses show the compositions of the schistose (I) ; 

 and massive serpentines (II), from Sprechenstein. 



i. ii. 



Si0 2 ... ... 40-55 ... ... 40-90 



Fe 2 3 ... ... 10-40 ... ... 7-68 



A1 2 3 ... ... 2-70 ... ... 2-08 



CaO ... ... 4-40 ... ... 0-30 



MgO ... ... 33-59 ... ... 37-45 



H 2 9-32 12-15 



100-96 100-56 



There was less unaltered salite in the massive than in the schistose rock. 

 Hence the difference in the amount of lime. 



The author concludes that the mother rock of the serpentine was an 

 augite rock belonging to the crystalline schists.' 1 * 



It is unnecessary to follow the author in his description of other 

 serpentines occurring along the same line of strike to the east in the Zillerthal 

 and the district of the Hohe Tauern. The rock from Windisch Matrey in 

 the latter district originally described by DRASCHE (see ante p. ,) is shown 

 to be a normal antigorite serpentine. Some of the other rocks investigated 

 by that author are proved to be oli vine- serpentines ; but most of them are 

 augite- (antigorite-) serpentines. 



The only other paper to which reference will be made in this historical 

 sketch is by SCHULZE, on the serpentines of Erbendorf , in Bavaria. These rocks 

 are associated with hornblende-schists, gneisses, talc- and chlorite-schists and 

 have been regarded by GUMBEL as due to the alteration of amphibolites. The 

 paper is extremely rich in petrographical details, but as no new type of 

 serpentine is described it will be sufficient to give the conclusions of the 

 author. 



(1) The description of the stratigraphical relations and petrographical characters of 

 these serpentines strongly suggests that the district in question has been profoundly affected 

 by regional metamorphism. The lenticular arrangement of the massive serpentines (augen- 

 or naser-structur on a large scale), the schistose character of the serpentine in certain places, 

 the interbanding with calcareous phyllites, are all features which can be readidy explained by 

 regional metamorphism, and which tend to negative the view that we are here dealing with a 

 stratigraphical sequence. 



