There can be no doubt that the existing Fauna and Flora is but the last term of a long series of equally numerous contemporary species, which have succeeded one another, by the slow and gradual substitution of species for species, in the vast interval of time which has elapsed between the deposition of the earliest fossiliferous strata and the present day.

We may observe in some of the abrupt grounds we meet with, sections of great masses of strata, where it is as easy to read the history of the sea, as it is to read the history of Man in the archives of any nation.