M. Studer on the Geological Structure of the Alps. 167 



rent divisions of the lias, of the inferior oolite, of the coral- 

 line and Portland oolite, are determined by their organic re- 

 mains, and are better separated than at any other point in the 

 Alps ; the upper Jura formation in particular, which appears 

 to be completely a stranger to the internal and oriental Alps, 

 here attains a remarkable development, and forms several 

 parallel chains. We remark also in many of these chains a 

 tendency to become arched, whereas in the Alpine chains the 

 beds are only prolonged on one side. The physiognomy of 

 the valleys reminds us of the softer and more uniform charac- 

 ter of the Jurassic valleys ; but nevertheless the forms are 

 more abrupt, the chains are not only cut transversely by 

 cluses,* but they also contain numerous oblique ravines, which 

 impart to these valleys a more picturesque and more varied 

 aspect. The limestone assumes the more the black tint of the 

 limestone of the Alps the nearer it approaches the central 

 masses of the Alps properly so called. The molasse, which 

 penetrates into all the large Jurassic valleys, is entirely awant- 

 ing in the Alpine Jura as well as in the Alps. This mixed 

 character is exhibited still more distinctly in the cretaceous 

 formation ; the nummulitic limestone, so largely developed in 

 the Alps and in a large portion of Southern Europe, does not 

 exist at all in the Alpine Jura. The Hippurite limestone, the 

 bed containing Inocerami, and the Neocomian strata, do not 

 penetrate into the Chablais, and are entirely strangers to the 

 interior of the Swiss Alpine Jura (district of En-haut, Ges- 

 senay, and the Simmenthal). They are there replaced by the 

 flysch, which attains a great development, occupying the bot- 

 tom of the enlarged valleys, rising to a great height on the 

 flank of the limestone chains, and forming even particular 

 chains, whereas it is completely awanting in the Jura. The 

 chain of the Niesen, the mountains of the Simmenthal, and 

 the district of Gessenay, are composed chiefly of flysch. The 

 calcareous masses of these same valleys, such as the Tour 

 d'Ay and Mayen above Aigle, and the Cornettes in Chablais, 

 are of the upper Jura formation. The Stockhorn and the Male- 



* The geologists of the Jura give the name of chtses to those cuts which 

 cross a mountain chain from one side to the other. When the rent is limited 

 to one of the flnnks^ it >« tevmccl I'nf:: — E. D, 



