44 M. Mohs' Summary of Geognoslical Phenomena. 



condary rocks (Flotzgebirge* ), which, leaving aside what can- 

 not come into consideration on account of its constitution, con- 

 sist of a small number of very slightly different mountain 

 rocks, and a knowledge of whose relations of superposition can 

 moreover be very easily acquired, in so far as it relates to the 

 discovery of useful minerals. 



The secondary rocks consist of sandstones, limestones (in- 

 cluding what are termed marls), gypsum, and clay. The por- 

 phyries, syenites, greenstones, amygdaloids, basalts, and other 

 rocks, which were formerly included among the secondary 

 rocks, but are at present regarded by most geognosts as for- 

 mations of a peculiar nature, are here excluded because there 

 is little or nothing to be sought for in them. 



The sequence of the various beds constituting the so-termed 

 rocks of the secondary series has been enumerated with ex- 

 treme minuteness, and in order to discover in this sequence a 

 universal regularity, it has been arranged in different forma- 

 tions, whose examination and thorough investigation form the 

 most important business of modern geognosy. There is, how- 

 ever, certainly no general agreement upon the subject ; and 

 whole formations and rocks are referred by some geognosts to 

 the secondary series, which by others are included in the tran- 

 sition class. In order to reconcile other discrepancies, what 

 are termed equivalents have been discovered or assumed ; but, 

 as it would appear, this plan has rather removed the object 

 more from the eye than brought it nearer. 



The following is the real state of the matter. The sequence 

 of the individual layers of the secondary rocks is constant, in 

 so far as one or other does not wedge out, or in so far as the 

 rock in the course of its continuation does not become con- 

 verted into another, as is very often the case with what are 

 termed primitive and transition rocks ; and they are never 

 found, either entirely or partially, much altered or reversed. 



* It must not be supposed from this, that the secondary rocks are confined 

 to the plains, and the transition and primitive rocks to the actual mountains, 

 although, certainly, the former occur more frequently in the lower tracts of 

 country, and the latter in the higher ; and it must also not be forgotten that 

 the division of mountain-masses into primitive, transition, and secondary 

 rocks is quite arbitrary. 



