Ch. II.] CHARACTER OF THE TERTIARY STRATA. 15 
a, will in other places be in contact with c, or with the lowest 
No. j. 
of the whole series, c7, 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 
