nts were redeemed from the water,
and all the earth was given to this new being for his home. Among all the
types born into the animal kingdom before, there had never been one to
which positive limits had not been set by a law of geographical
distribution absolutely impassable to all. For Man alone those boundaries
were removed. He, with the domestic animals and plants which were to be
the companions of all his pilgrimages, could wander over the whole earth
and choose his home. Placed at the head of creation, gifted with intellect
to make both animals and plants subservient to his destinies, his
introduction upon the earth marks the last great division in the history
of our planet. To designate these great divisions in time, I would urge,
for the reasons above stated, that the term which is indeed often, though
not invariably, applied to them, be exclusively adopted,--that of the Ages
of Nature.

But these Ages are themselves susceptible of subdivisions, which should
also be accurately defined. What is the nature of these subdivisions? They
are all connected with sudden physical changes in the earth's surface,
more or less limited in their action, these changes being themselves
related to important alterations in the organic world. Although I have
stated that one general character prevailed during each of the Ages, yet
there was nevertheless a constant progressive action running through them
all, and at various intervals both the organic and the physical world
received a sudden impulse in consequence of marked and violent changes in
the earth-crust, bringing up new elevations, while at the same time the
existing animal creation was brought to a close, and a new set of beings
was introduced. These changes are not yet accurately defined in America,
because the age of her mountains is not known with sufficient accuracy;
but their limits have been very extensively traced in Europe, and this
coincidence of the various upheavals with the introduction of a new
population differing entirely from, the preceding one has been
demonstrated so clearly that it may be considered as an ascertained law.
What name, then, is most appropriate for the divisions thus marked by
sudden and violent changes? It seems to me, from their generally accepted
meaning, that the word Epoch or Era, both of which have been widely,
though indiscriminately, used in geology, is especially applicable here.
In their common use, they imply a condition of things