ANNIVEKSAKT ADDRESS OF THE PEESIDENT. CI 



The principal dolomite also thins ont towards the Plassegger 

 Pass. It is uncertain whether the dolomite of Monbiel belongs 

 here, or is an altered Dachstein-limestone. 



The Koessen beds do not appear to occur eastwards of tlie 

 Geiss-spitze, on the Ofentobel. 



The following are some of the principal results of the examina- 

 tion of the Selvretta-stoclc, not far from Cernetz, in the Lower 

 Engadin. 



1. The whole central mass consists of crystalline rocks : gneisa, 

 mica-schist, and hornblende-schist ; on its outer flanks first ap- 

 pear Casauna-schists and sedimentary rocks ; no granite or erup- 

 tive rock is visible in this mass, only on the southern flank on the 

 borders of the sedimentary rocks in Lower Engadin, and rather 

 in the strike of the anticlinals. 



2. The chief mass of the Selvretta is an exploded or burst dome 

 or saddle, the elevation of which was probably caused by the meta- 

 morphism of the rocks ; the narrow ridges with their flaggy beds 

 are the scattered crusts or outer layers of this dome-shaped mass : 

 the inner points are not the most elevated ; but the main line or 

 centre of elevation is marked by a depression, on each side of which 

 the strata or beds dip outwards from this line. 



On the western side the elevating force must have been repeated 

 with greater intensity, as the crystalline rocks are here forced in 

 a fan-shaped form over the sedimentary rocks. 



The boundary of this mass towards the Eluela Scaletta Mountain, 

 which also forms a portion of the whole central mass, is not acci- 

 dental, but is caused by the coincidence or combination of the 

 action of two centres of elevation which operated with less in- 

 tensity on the line between Klosters and Lavin, marked by the 

 valleys of Vareina and Sagliains, whilst, owing to a greater in- 

 tensity of force, the burst dome of the Selvretta rose up on the 

 one side, and the fan-shaped mass of the Scaletta on the other. 

 The beds between the two were pressed together and crumpled 

 up, but here the two crystalline masses are not separated by any 

 line of sedimentary rocks. 



These two instances will serve to show how Prof. Theobald has 

 executed the laborious task he has undertaken, without troubling 

 you with an account of the other central masses which he has de- 

 scribed. When similar observations shall have been made on 

 other portions of the Alps — a task which has already been done to 

 some extent by Prof. Studer — we shall have a clearer view of the 

 gigantic operations of nature which have led to the elevation and 

 structure of this typical region. 



Prof E. Desors has also publislied a work on the structure of 

 the Alps, in which he endeavours to show the laws and causes 

 which have led to the development of their pi'esent forms. These 

 outward forms depend on two conditions, the nature of the rocks 

 of which they are composed, and the intensity of the force by wliich 

 they were elevated. Eecent investigations have ujiset the ancient 

 theories that all the highest points consisted of crystalline rocks, 



