l6 GEOLOGICAL BIOLOGY. 



classifying rocks the larger aggregates were naturally moun- 

 tain masses. As the conception of movements in the earth's 

 crust with folding and displacement came into the science, 

 the idea of classification and grouping of rocks was retained, 

 but that their grouping was based upon present massing above 

 the surface as mountains ceased to be accepted as truth. In 

 the German language the term " Gebirge" was retained, and 

 apparently with restricted meaning. Kirwan apparently trans- 

 lated the term directly into English as mountains. Formation, 

 however, took the place of mountain, as applied to rock classi- 

 fication, in the early part of the century. 



The Formation of Sedimentary Rocks according to Werner and 

 his School. In the following cut is illustrated the conception 

 of the Wernerian school of the mode of formation of the 

 rocks and the reason for the relative positions each kind occu- 

 pies. In the figure a a' a is the supposed fundamental basin 

 of primitive rocks crystallized out from the chaotic fluid as 

 described above by Lehmann, and these rocks were hence 

 named Urgebirge, or Primitive rocks. When the ocean 



a 



FIG. i. Diagram expressing the supposed mode of formation of the several formations {Gebirge) 

 according to the Wernerians. (After Conybeare & Phillips.) 



level had sunk to b b, deposition began and went on till the 

 rocks b b' b' b' b were formed, the Uebergangsgebirge or tran- 

 sition rocks of Werner, whose position is oblique because of 

 conformity to the sides of the original mountains as they 

 stood in the original seas. As the surface of the ocean con- 

 tinued to sink, the deposits were accumulated lower and 

 lower down on the mountain-sides, and more and more 

 nearly horizontal, c c'c'c and d d'd, which represent the 

 Floetzgebirge or flat-lying rocks; finally above the neues 



