Royal Academy of Berlin. 333 



which traverse four or five times the whole breadth of the chain, 

 and with their deep inlets and sections. This being exactly the form 

 and structure of the great coral reef which surrounds New Holland, 

 we may be inclined to ascribe to both a similar mode of origin. The 

 chalk formation draws itself close up from the exterior so as to sur- 

 round the Jura ranges, but in the interior of the encompassed coun- 

 try there is not a trace of it to be found. From this we have evi- 

 dence of the mural elevation of the Jura existing previous to the de- 

 position of the chalk. 



The Jura range is divided by nature into three parts : 1 . The 

 Swiss Jura, in which the layers are always much inclined, and form 

 long extended ridges and chains ; 2. The Swabian Jura, in which 

 the layers lie regularly and horizontally upon one another, and form a 

 large plateau little undulated and extending over many miles ; 3. The 

 Franconian Jura, in which the middle is occupied by extended masses 

 of dolomite, which appear on the heights like obelisks, towers, or 

 ruins of gothic castles. This appearance of dolomite begins almost 

 exactly where the Jura changes its north-easterly for a northern di- 

 rection. The dolomite is no new superadded mass ; one series of 

 strata would be deficient, were we to consider it a Jurassic stratum 

 which had hitherto not occurred. Besides, it possesses no peculiar 

 zoological character, and for this reason gives indications of its origin 

 from the metamorphosis of limestone. 



In height or section the Jura ranges may also be divided into three 

 parts : 1, a black one, the layers of lias and shales ; 2, a brown, the 

 coarse brown sandstone ; 3, a white one ; fine-grained layers of lime- 

 stone, coral, and shell banks. A description and catalogue of the cha- 

 racteristic fossils of each layer of these divisions gives a more clear 

 and accurate idea of them and of their zoological character, than the 

 long, and frequently inaccurate descriptions often given, in which 

 the same thing is frequently repeated under different names. 



The lias, which makes its appearance almost everywhere at the foot 

 of the mountains, contains almost nothing, but such organic pro- 

 ducts as are peculiar to it alone, and these products in general are 

 the same in all countries hitherto examined. 



The middle part of the Jura is more varying. That which appears 

 in the southern parts of England and in France in the form of oolite, 

 is in Germany a coarse sandstone, with analogous shells in it ; but 

 in the north of England this sandstone contains a quantity of im- 

 pressions of plants, and even coal, which are quite similar to those 

 which we on the other hand find in the keuper, recollecting that in 

 other organic products both formations have nothing in common with 

 each other. 



