THE CENTURY'S PROGRESS IN GEOLOGY 



JAMES DWIGHT DANA 



tion of the origin of the 

 " primary " rocks. It re- 

 quired but little observa- 

 tion to show that the ex- 

 act succession of strata 

 is never precisely the 

 same in any widely sep- 

 arated regions. Never- 

 theless, there was a germ 

 of truth in Werner's sys- 

 tem. It contained the 

 idea, however faultily in- 

 terpreted, of a chronolog- 

 ical succession of strata ; 

 and it furnished a work- 

 ing outline for the observers who were to make out the 

 true story of geological development. But the correct 

 interpretation of the observed facts could only be made 



after the Huttonian view 

 as to the origin of strata 

 had gained complete ac- 

 ceptance. 



When William Smith, 

 having found the true key 

 to this story, attempted 

 to apply it, the territory 

 with which he had to 

 deal chanced to be one 

 where the surface rocks 

 are of that later series 

 which Werner termed sec- 

 ondary. He made numer- 

 rous subdivisions within 

 137 



SIR RODERICK IMPEY MURCHISON 



