1848.] 



MURCHISON ON THE STRUCTURE OF THE ALPS. 



211 



"flysch'* during the period of its formation. As he mainly sup- 

 ports that view by the example of certain granitic blocks of the valley 

 of Habkheren near Interlacken, and as the interstratification of such 

 boulders or blocks in strata of that age must be very novel to En- 

 glish geologists, I crave permission to digress from the chief objects of 

 this memoir, in order to discuss a point, which, according to M. 

 Studer, is closely related to the structure of the " flysch." 



In the valley of Habkheren, on the north bank of the lake of 

 Thun (as in many interior valleys of the calcareous chains of the 

 Swiss Alps), the flysch is squeezed up in a narrow trough with 

 broken and highly inclined strata, portions of which are exhibited 

 on the right-hand side of the hill road which ascends from Inter- 

 lacken to Habkheren. That these beds belong to the true supracre- 

 taceous flysch is undoubted, because in rising up they overlap the 

 nummulitic limestone at the head of the valley, which rock in its 

 turn surmounts the neocomian limestones of the adjacent chain. 

 These "flysch " rocks, in parts pebbly and gritty, in parts schistose, 

 together with the usual shale and thin-bedded, dark, impure white- 

 veined limestones of this series, are there seen to contain truly inter- 

 calated geodes and bands of a granitoid character, which re-occur at 

 intervals in a distance of about 150 paces, much in the manner re- 

 presented in the diagram (fig. 20), the granitic geodes often imitating 



Greenish crystalline granitic course. 

 Alternations of schist and impure lime- 

 stone or "flj'sch." 

 Granitic geodes. 

 Schist and limestone, &c. 



5. Quartzose granitic band. 



6. Black schists with calcareous concretions. 



7. Schists with granitic concretions. 



8. Schists and limestones overlaid by grani- 



toid conglomerates, &c. 



in form the calcareous nodules ! My attention was first directed to 

 this section by Professor Studer, in company with whom and M. Me- 

 rian and M. Favre, I visited it. It appeared to me, that the granitoid- 

 like concretions are there intercalated with calcareous nodules, as 

 well as that the thin granitic courses alternate with the schists and im- 

 pure limestones. The largest of the concretions visible in the course 

 (3) is an oblate spheroid about four feet long by three feet wide ; 

 the external zone being more schistose, the interior passing from a 

 paste with large crystals of felspar to a more compact nucleus, one 

 extremity of which seemed almost as if made up of small granite 

 pebbles. The band (5), on the other hand, appeared to be an uniform 

 greenish-coloured granite or granitic gneiss. 



I confess that I could not account for such appearances, except by 

 supposing that the granitic matter was evolved contemporaneously 

 with the formation of the sedimentary sandstones and schists which 

 envelope it ; the concretionary forms of some of these masses seeming 



