THE MAKING OF THE GEOLOGICAL TIME-SCALE. 21 



whole field of investigation into the history and evolution of 

 organisms. Cuvier and Brongniart, applying their methods 

 of analysis to the rocks of the Paris basin, succeeded in clas- 

 sifying them into strata, and in defining the separate strati- 

 graphical divisions in terms of the contained fossils. The 

 Paris basin rocks, being found to lie above the Cretaceous 

 rocks of France and England which represent the top mem- 

 ber of the secondary formation of the Lehmann classification, 

 were named Tertiary to indicate their geological importance 

 and their relative position in the geological scale. These 

 naturalists did not, however, perfect the geological classifica- 

 tion which their biological studies suggested. 



William Smith and Lyell — William Smith in England * em- 

 phasized the value of fossils as means of identifying strata in 

 different regions, and others had some part in the elaboration 

 of the principle involved, but Lyell, more than any one else, 

 perfected the scheme of classification of geological formations 

 on the basis of their fossil contents. 



Lyell's Classification of the Tertiary into Eocene, Miocene, and 

 Pliocene. — The first attempt to use fossils as the fundamental 

 basis of a classification of geological formations was made by 

 Lyell in the classification of the Tertiaries of England. In 

 the second edition of his "Elements of Geology," published 

 in 1841, we find him saying: "When engaged, in 1828, in 

 preparing my work on the Principles of Geology, I conceived 

 the idea of classing the whole series of Tertiary strata in four 

 groups, and endeavoring to find characters for each, expressive 

 of their different degrees of afifinity to the living fauna." f A 

 mathematical comparison was made between the proportion- 

 ate numbers of recent and of extinct species in the several 

 divisions of the Tertiary rocks of England. The result is 

 given in the following table : X 



Period. Locality. 



Post-Pliocene, Freshwater. Thames Valley, 



Newer Pliocene, Marine Strata ne^r Glasgow, 



Older Pliocene, Norwich Crag, 



Miocene, Suffolk, red and coralline Crag, 



Eocene, Lontlon atid Hampshire, 



* "Tabular View," 171^0, and in unpublished maps and sections of the first 

 and second decades of this century. 



f p. 280. X Copied from his " Elements," 2d ed., vol. i. p. 2S4. 



