1 86 THE JOURNAL OF GEOLOGY. 



Lehmann's classification, in so far as it goes, expressed estab- 

 lished facts of nature. There are Primitive, Secondary, Tertiary 

 and Quaternary formations, but the theory that they may be 

 defined and determined by physical structure and present rela- 

 tive position is only approximately true. All crystalline rocks 

 are not primitive, all the secondary rocks are not merely'consoli- 

 dated fragments of primitive rocks. Some of them are fully 

 metamorphosed. All Tertiary rocks are not unconsolidated, as 

 the Tertiaries of California illustrate, and we now know that alti- 

 tude above the sea, or relative position of the various formations, 

 are by no means uniform and form no criterion for their determi- 

 nation. 



The next important advance in the classification of rocks was 

 started by Werner and his pupils. It was a classification based 

 upon the mineral constitution of the rocks. As the study of 

 geology advanced Lehmann's classification was found difficult to 

 apply with precision, and it was found to be unnatural in that 

 rocks of apparently similar kind were dissociated, while rocks of 

 unlike character were brought into the same class. And the min- 

 eral character and composition of rocks was found to be an accu- 

 rate means of defining them. As the mineral characters became 

 clearly understood, the rock masses received their names from 

 the chief minerals in them, and finally the mineral nomenclature 

 entirely superseded the nomenclature of Lehmann, and a second 

 classification arose in which the theory of the original order of 

 formation of the rocks gave place to the actual sequence of min- 

 eral aggregates, one after another, in examined sections of the 

 earth's crust. In this study of minerals Werner was a conspicu- 

 ous leader, and the classifications at the beginning of the present 

 century were mainly his or adaptations of them. The form 

 which the geological scale assumed in English geological sys- 

 tems is seen in typical form in Conybeare and Phillip's Geology 

 of England and Wales, 1822. 



Arranged in order from above downwards, it is as follows : 

 I. Superior order. (Neues Floetzgebirge, of Werner). 

 II. Superme dial order. (Floetzgebirge, " 



