227 



May 21. — Grenville Lonsdale, Esq. Ensign in the Third Foot, was 

 elected a Fellow of this Society. 



A Paper was read, entitled " A Sketch of the Structure of the 

 Austrian Alps;" by the Rev. Adam Sedgwick, Pres. G.S. F.R.S. 

 Woodwardian Professor in the University of Cambridge, &c, and 

 Roderick Impey Murchison, Esq. Sec. G.S. F.R.S. &c. &c. 



The authors, after briefly noticing some of the memoirs which have 

 been written in explanation of the geological structure of the Alps, 

 proceed to exhibit the results' of their own observations, made in the 

 summer of 1829, during several traverses among the eastern parts of 

 the chain. They state that the structure of the eastern Alps, when 

 considered only in a general point of view, is of great simplicity ; the 

 chain being composed of an axis of primary and transition rocks, 

 chiefly of a slaty texture ; flanked and surmounted by two great se- 

 condary calcareous zones, which are in their turn surmounted by 

 tertiary deposits, descending on one side into the plains of Italy, and 

 on the other side into the elevated plains of the Upper Danube. They 

 then notice the extraordinary derangements in the position of some 

 of the great mineral masses of the Alps ; and afterwards describe in 

 considerable detail a section from the plains of the Friuli to the valley 

 of the Traun near Salzburg over the metalliferous hills of Bleiberg, 

 and over the crests of the Katsberg and Tauern Alp. They also de- 

 scribe a second section parallel to the former, from the primary moun- 

 tains of Gastein, through the saliferous deposits of Hallein and the 

 hippurite-limestone of Untersberg to the tertiary piains of Bavaria. 



The formations appearing in the lines of these two sections are the 

 following, in ascending order : — 



1. Primary rocks forming the central axis. — The range of the pri- 

 mary peaks, eastwards from the confines of the Tyrol, is described. 

 It is remarked that as the chain decreases in elevation in its range 

 eastward, the prevailing character of granitoid gneiss gives way to 

 that of mica schist ; it is then stated that in both the sections these 

 rocks pass into the next superior system through the intervention of 

 chloritic schist with subordinate beds of crystalline, white limestone. 



2. Crystalline rocks containing calcareous beds, with traces of organic 

 remains and graduating into other rocks conforming to the ordinary tran~ 

 sition type. — This series contains many beds not to be distinguished 

 from the former class ; but it appears to be characterized by a greater 

 quantity of limestone, many parts of which are perfectly crystalline. 

 At the southern base of the Tauern the authors discovered mica-slate 

 with garnets, and chlorite-slate containing thin layers of white dolomite, 

 alternating with thicker beds of a dark blue colour, containing many 

 encrinital stems. The whole system is described as passing into a 

 series of calcareous peaks, some of which rise to the height of nearly 

 9000 feet above the level of the sea. The whole series is considered 

 to terminate with a system of beds, composed of variously coloured 

 shales, passing into grauwacke-slate, alternating with greenish-gray 

 and reddish fine-grained grauwacke-sandstone, subordinate to which 

 are beds of highly calcareous slate and limestone, and masses of 

 sparry iron ore. The authors give some details respecting the chief 



