242 GENERALIZATIONS. 



rises (as at the Weissenstein and the Blauenberg) into a lofty 

 dome, it is surrounded by a valley, in the same manner as a 

 fortress is girt round with a ditch and a wall. 



Mountain-chains may thus be classified into different orders. 

 Those chains formed by saddle-shaped mountains (with the arch 

 complete) were called by Thurmann chains of the first order ; 

 those produced by the ridges on the opened arch were named 

 chains of the second order] and those originating from the diffe- 

 rent rock -formations of the denuded arch were styled chains of 

 the third and fourth orders, according as two or more of these 

 formations surrounding the arch appeared as distinct chains* 

 (fig. 362) . In all these cases there is a regular sequence of all 

 the higher strata on both sides of the upheaved mountain ; those 

 of the same age correspond to one another, and in the interior 

 of the chain are directly connected. 



In a second class of the phenomena of elevation an interrup- 

 tion is produced throughout the whole thickness of the stratified 

 rocks, and the correspondence of the beds of the same age in 

 the two chains is entirely destroyed. This mode of upheaval 

 has been subject also to numerous modifications. Sometimes 

 only one margin of the stratified mass is upheaved, and projects 

 often several thousand feet above the other edge, which retains 

 its original position or nearly so (fig. 363), so that its oldest bed 

 comes into contact with the newest ; sometimes both edges are 

 thrown up, but very unequally (fig. 364), so that the strata in 

 the two no longer coincide; or the edges are upraised (fig. 365), 

 or inverted, and turned one over the other, so that newer rock- 

 beds come to lie beneath the older ones. 



The fissures running deep into the earth which are produced 

 by these fractures of the rocks allow water to come to the sur- 

 face, here and there, from great depths, and in these cases afford 

 evidence of internal high temperature. Prof. Moussori has as- 



* Thurmann subdivided the Jura into 162 chains. Of these he referred 

 30 to the first order (such as the Saleve and Dole), 80 to the second order 

 (Chasseron, Blauenberg), 40 to the third order (Geissfluh, Lagern), and 12 

 to the fourth order (Passwang, Geissfluh). He reckons 100 basin-valleys, 

 and 90 transverse clefts through mountain-chains. (See his " Resume des 

 lois orographiques generates du systeme des Monts Jura," in the ( Memoires 

 de la Socie'te' Helve tique des Sciences ' for 1863.) 



