Professor Favre on the Geology of the German Tyrol. 79 



but, to our great surprise, we scarcely met with anything 

 else than limestones. Above Heiligen-Blut we traverse 

 green slates and slaty cipolins with Avhite mica, the strata 

 dipping nearly to the south. We soon reach argillo-talcose 

 slates containing garnets, accompanied with dolomite and 

 saccaroidal limestone. After advancing about three hours, 

 we find ourselves on a kind of plateau, terminating in a 

 circus, the beds of which are horizontal. When we reach 

 the highest part of this circus, formed by argillo-talcose 

 garnetiferous slates, the green slates likewise containing 

 girnets and quartzite, rather in veins than in beds, we have 

 g lined the summit of the pass. 



Fi'om the commencement of the descent, we find large beds 

 of saccaroidal limestone more or less micaceous. The green, 

 or argillo-talcose slates, alternate with limestones, and form, 

 vsith some dolomites and cargneules, all the northern acclivity 

 of the pass as far as Tauernhaus, where serpentine occurs. 

 The horizon tality of the beds at the summit of the pass ap- 

 pears to continue as far as the junction of the Seidlwinkel- 

 Thal and Rauris -Thai, and beyond, the strata dip to the noi'th. 

 To recapitulate : We have seen in this pass, 1*/, That the 

 central chain was formed, not of crystalline rocks, but in a 

 great part of limestones and slates, which are evidently sedi- 

 mentary rocks more or less altered ; 2d, That these sedimen- 

 tary formations form a saddle or arch ; for, on the side of Heili- 

 gen-Blut, they dip to the soutli ; on the summit of the pass 

 they are horizontal, and, on the northern acclivity, they dip 

 to the north. It is probable that this arch covers the pro- 

 longation of the granitic rocks of the bottom of the valley 

 of Gastein, and that the formations composing the actual 

 arch are only a very small part of that which formerly had 

 a tendency to become formed when the upraising of the cen- 

 tral chain lieaved up the great masses whicli form the second- 

 ary chains of the Tyrol. 



The argillo-talcose slates and saccaroidal limestones alter- 

 nate in a general way with the green slates, which are mure or 

 less serpentineous, chloriteous, or talcose, and which are no- 

 thing more than modifications of the first of these rocks ; as a 

 proof of this, we may refer to the numerous instances in whicli 



