enough to
change the general aspect of the organic world. This age was throughout,
in its physical formation, the age of large continental islands; while in
its organic character it was the age of Reptiles as the highest animal
type, and of Gymnosperms and Monocotyledonous plants as the highest
vegetable groups.

[Footnote 2: I say nothing of the traces of Birds in the Secondary
deposits, because the so-called bird-tracks seem to me of very
doubtful character; and it is also my opinion that the remains of
a feathered animal recently found in the Solenhofen lithographic
limestone, and believed to be a bird by some naturalists, do not
belong to a genuine bird, but to one of those synthetic types
before alluded to, in which reptilian structure is combined with
certain birdlike features.]

There was an age in the physical history of the world when great ranges of
mountains bound together in everlasting chains the islands which had
already grown to continental dimensions,--when wide tracts of land,
hitherto insular in character, became soldered into one by the upheaval of
Plutonic masses which stretched across them all and riveted them forever
with bolts of granite, of porphyry, and of basalt. Thus did the Rocky
Mountains and the Andes bind together North and South America; the
Pyrenees united Spain to France; the Alps, the Caucasus, and the Himalayas
bound Europe to Asia. The class of Mammalia were now at the head of the
animal kingdom; huge quadrupeds possessed the earth, and dwelt in forests
characterized by plants of a higher order than any preceding ones,--the
Beeches, Birches, Maples, Oaks, and Poplars of the Tertiaries. But though
the continents had assumed their permanent outlines, extensive tracts of
land still remained covered with ocean. Inland seas, sheets of water like
the Mediterranean, so unique in our world, were then numerous. Physically
speaking, this was the age of continents broken by large inland seas;
while in the organic world it was the age of Mammalia among animals, and
of extensive Dicotyledonous forests among plants. In a certain sense it
was the age of completion,--the one which ushered in the crowning work of
creation.

There was an age in the physical history of the world (it is in its
infancy still) when Man, with the animals and plants that were to
accompany him, was introduced upon the globe, which had acquired all its
modern characters. At last the contine