Ch. II.] CHARACTER OF THE TERTIARY STRATA. 15 



a, will in other places be in contact with c, or with the lowest 



No. 1. 



of the whole series, c?, all the intermediate formations being 

 absent. 



Tertiary formations. After some progress had been made 

 in classifying the secondary rocks, and in assigning to each 

 its relative place in a chronological series, another division ot 

 sedimentary formations was established, called tertiary, as being 

 of newer origin than the secondary. The fossil contents of 

 the deposits belonging to this newly-instituted order are, upon 

 the whole, very dissimilar from those of the secondary rocks, 

 not only all the species, but many of the most remarkable 

 animal and vegetable forms, being distinct. The tertiary for- 

 mations were also found to consist very generally of detached 

 and isolated masses, surrounded on all sides by primary and 

 secondary rocks, and occupying a position, in reference to the 

 latter, very like that of the waters of lakes, inland seas, and 

 gulfs, in relation to a continent, and, like such waters, being 

 often of great depth, though of limited area. The imbedded 

 organic remains were chiefly those of marine animals, but with 

 frequent intermixtures of terrestrial and freshwater species so 

 rarely found among the secondary fossils. Frequently there 

 was evidence of the deposits having been purely lacustrine, a 

 circumstance which has never yet been clearly ascertained in 

 regard to any secondary group. 



We shall consider more particularly, in the next chapter, 

 how far this distinction of rocks into secondary and tertiary is 

 founded in nature, and in what relation these two orders of 

 mineral masses may be supposed to stand to each other. But 

 before we offer any general views of this kind, it may be useful 

 to present the reader with a succinct sketch of the principal 



