while _Eos_ signifies dawn, _Meion_ less,
and _Pleion_ more. Thus Eocene indicates the dawn of recent species,
Pliocene their increase, while Miocene, the intermediate term, means
less recent. Above these deposits comes what has been called in
science the present period,--_the modern times_ of the geologist,--that
period to which man himself belongs, and since the beginning of which,
though its duration be counted by hundreds of thousands of years,
there has been no alteration in the general configuration of the
earth, consequently no important modification of its climatic
conditions, and no change in the animals and plants inhabiting it.

[Illustration: CRUSTACEA.--DEVONIAN PERIOD.]

[Illustration: FISH OF THE DEVONIAN PERIOD.]

[Illustration: FISH OF THE CARBONIFEROUS PERIOD.]

[Illustration: FOSSIL VEGETATION OF CARBONIFEROUS PERIOD.]

[Illustration: FISH OF THE PERMIAN PERIOD.]

I have spoken of the first of these periods, the Azoic, as having
been absolutely devoid of life, and I believe this statement to be
strictly true; but I ought to add that there is a difference of
opinion among geologists upon this point, many believing that the
first surface of our globe may have been inhabited by living beings,
but that all traces of their existence have been obliterated by the
eruptions of melted materials, which not only altered the character of
those earliest stratified rocks, but destroyed all the organic remains
contained in them. It will be my object to show, not only that the
absence of the climatic and atmospheric conditions essential to
organic life, as we understand it, must have rendered the previous
existence of any living beings impossible, but also that the
completeness of the Animal Kingdom in those deposits where we first
find organic remains, its intelligible and coherent connections with
the successive creations of all geological times and with the animals
now living, afford the strongest internal evidence that we have indeed
found in the lower Silurian formations, immediately following the
Azoic, the beginning of life upon earth. When a story seems to us
complete and consistent from the beginning to the end, we shall not
seek for a first chapter, even though the copy in which we have read
it be so torn and defaced as to suggest the idea that some portion of
it may have been lost. The unity of the work, as a whole, is an
incontestable proof that we possess it in its original integrity. The
validit