86 Prof. Sedgwick and Mr. Murchison on the 



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It forms no part of our object to give any detailed account 

 of the mineral structure of the central axis ; we may however 

 observe, that as it decreases in elevation in its range towards 

 the east, its prevailing character of granitoid gneiss seems to 

 give way to that of mica-schist and some other primary slaty 

 rocks. 



In the higher part of the valley of Gastein the principal 

 rocks we observed were the following: (1) Granite; (2) Gra- 

 nitoid gneiss, alternating near the highest waterfall with thin 

 beds of white, granular marble; (3) A very feldspathic variety 

 of mica-schist, here and there containing garnets; (4) The 

 same variety often passing into white-stone, also here and 

 there becoming quartzose and graduating into slaty quartz- 

 rock ; (5) Mica and chlorite slates, &c. &c. Some of these 

 varieties below Hof Gastein, and close to the transition series, 

 alternate with thin beds of a beautiful greenish, striated marble 

 resembling cipollino. 



Above Gasteiner Bad several of the slaty masses contain 

 small disseminated crystals of auriferous pyrites; and in one 

 of the precipices in the highest part of the valley, gold mines 

 have been worked at the height of 7800 Vienna feet above 

 the level of the sea. Similar mines have been worked in the 

 adjoining peaks of the Raurisberg at the height of 9080 feet 

 above the same level *. 



In the traverse we made through the primary system over 

 the Katsberg, from Spital on the Drave to St. Michael 

 on the Mur, the prevailing rocks were mica-schist; and we 

 have already remarked that for many miles along the great 

 longitudinal valley of the Drave they have a decided dip to 

 the south, carrying them unequivocally under the transition 

 rocks, hereafter to be noticed, which form the base of the 

 Bleiberg ridge. 



Between Gmiind and Rennweg the rocks contain abun- 

 dance of garnets ; and not far from the latter place there are 

 subordinate masses of serpentine in the mica-schist. On the 

 south ascent of the Katsberg, the prevailing rock is a beauti- 



from the higher peaks of the Tyrol towards the east, and the great ex- 

 pansion of the southern calcareous zone of the Alpine chain, produce an 

 effect upon the hydrography of the whole region which deserves notice. 

 The calcareous zone not only becomes greatly expanded; but near the 

 commencement of the Julian Alps gives off a second chain, extending into 

 the provinces on the eastern shores of the Adriatic. The consequence is, 

 that the parting of the waters between the Black Sea and the Adriatic 

 takes place, in all the country east of the Adige, among the higher eleva- 

 tions of the secondary calcareous system. West of the Adige, the parting 

 of the waters takes place among the crests of the central axis. 

 * In English feet the respective heights are 8135 and 9470. 



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