M. Stutler on the Geological Sir iic lure of Ihe Alps. 149 



portions in the mica slate and gneiss. In this case the lime- 

 stone is generally converted into white or coloured marble, 

 or into dolomite, and the slates become shining and acquire 

 all kinds of tints, such as red, brown, green, &c. 



It is difficult to define the relations which subsist between the 

 flysch and the rocks of the central masses. Generally we see 

 the flysch and a greyish limestone rising from beneath the cen- 

 tral masses, and thus forming the lowest portion visible of the 

 Alpine system. Above the flysch there lie mica-slates or 

 gneissitic quartzites, which often occupy an extent of several 

 leagues ; and above them comes the true gneiss. The stratifi- 

 cation, at first parallel to that of the flysch, gradually becomes 

 inclined and then vertical, and finishes by acquiring a totally 

 opposite inclination on the opposite side of the group, where 

 again we find appearing, under the last crystalline-slates, the 

 marl-slates 'and the ordinary grey limestones. Most frequently^ 

 however, the limit between the slates of the flysch and the 

 mica-slates is so vague that it is impossible to say where the 

 one series terminates and the other begins ; the flysch gene- 

 rally becomes shining, it assumes varied colours, and we per- 

 ceive in its interior, masses of true mica-slate and quartzite ; 

 we believe ourselves already surrounded on all sides by rocks 

 belonging to the central masses, when suddenly the flysch and 

 the calcareous slates make their appearance anew, and often 

 it is only after having walked for whole hours amidst these 

 alternations, that we are assured of having really entered the 

 domain of the crystalline rocks. 



Limestone and Slate. — The state of matters is different at 

 the contact of the central masses with the large deposits of 

 limestone and slate which surround them on the north. The 

 rock which touches the secondary beds is generally not mica- 

 slate, but an imperfectly slaty quartzite, sometimes containing 

 felspar, and whose stratification is distinct only towards the 

 interior of the central mass, where it becomes transformed into 

 a true gneiss or into gneissitic granite ; its beds then become 

 vertical, and even dip to the south. The sedimentary rocks 

 are in discordant stratification with this quartzite ; they are 

 inclined to the north, and their beds, which follow the exter- 

 nal slope of the gneiss, dip at first under very high angles ; 



