M. Stiider on the Geological Structure of the Alps. 145 



that is to say, from the sources of the Aar to those of one of 

 the tributaries of the Rhone, and on the following day crossing 

 the Simplon in a comfortable carriage, would not fail to be- 

 lieve that it was during his first day''s journey that he had tra- 

 versed the water-shed, and had passed the central chain. The 

 same traveller would form a very different opinion, if, in order 

 to reach Italy, he had the first day crossed the Gemmi, and the 

 second the Col of St Theodule. 



A profound study of the system of the Alps has caused M. 

 Studer, and all the geologists who have examined the Alps with 

 care, to abandon the idea of a central chain flanked by parallel 

 secondary chains. According to M. Studer, the Alps are di- 

 vided into (jroups, forming so many distinct central masses, 

 which run, for the most part, in the same direction, but which 

 frequently, in relation to one another, follow an oblique course, 

 or are arranged like the squares of a chess-board around a 

 central axis, nearly similar to the different crater- cones be- 

 longing to the same volcanic zone. The intermediate spaces 

 between the central masses contain particular formations, 

 whose structure and mineralogical nature are related to those 

 of the principal masses ; it is in these formations that the most 

 of the interior valleys of the Alps are hollowed, and it is to 

 these that the greater number of the Cols correspond. The 

 secondary formations, such as the limestones, the slates, and 

 the sandstones, stretching along the northern edge, and partly 

 along the southern edge of the high Alps, are intimately con- 

 nected with the formations proper to the interior valleys ; wit- 

 ness, for example, the rocks of the valleys of Frutigen and of 

 Gessenay, which continue without interruption into the Valais, 

 stretching to the east, by the Nuffenen, as far as the southern 

 side of the St Gothard, and to the south, by the Great St 

 Bernard and the neighbouring rocks, into Piedmont. In the 

 same manner also, the limestones and the slates of Coire and 

 of Prettigau, extend to the south over the axis of the Alps, into 

 the Upper Engadine, and as far as Bormio, to unite themselves 

 with the limestones of the Alps of Lombardy, after having 

 traversed the whole Alpine system. 



In the present state of our knowledge, it is not possible to 

 determine the limits of all the central masses of the system of 



VOL, XXXIII. NO. LXV. JULY 1842. K 



