Page:Popular Science Monthly Volume 67.djvu/477

Rh closing Bering Straits and the English Channel, enabled them to spread all over the northern hemisphere and even into the southern, for in the next age, the Eocene, we find their remains in far-off Australia and New Zealand, while others occur in Alaska, stragglers from the migration into Asia.

The great frozen north of to-day had not yet been hinted at, a warm, if not subtropical, climate prevailed even in the far north, and Greenland was the garden spot that its name implies. On its western coast many plant-beds have been discovered, containing the remains of tree-ferns, cycads, incense cedars, figs, camphor trees, magnolias, eucalypts and other natives of warm climes. This northern region with numerous land connections to lower latitudes was probably the original home of our modern floras and faunas, which spread southward in successive waves of migration. We know that the Mid-Cretaceous witnessed the apparently sudden appearance of a host of new and higher plant types, and the basal Eocene witnessed, a like sudden appearance of mammalian types. It is to the frozen north of to-day that we look, hopeful that it will shed light on ancestral forms that flourished there in the far distant past.

With the ushering in of the Eocene period the gigantic reptiles are entirely replaced by higher types; small mammals, some races of which soon attained great size, uncouth beasts long since passed away, besides the remote and generalized ancestors of some of our modern animals. It is in the rocks of this period that we find the dainty little four-toed ancestor of the horse. The Eocene, together with the next period, the Oligocene, represents a couple of million years, during which the sequoias were almost as abundant and widespread as are the pines in our existing flora. In Fig. 4 are shown some of the characteristic animals of these periods, and in Fig. 1 we get some idea of the geological and floral conditions. In the far west this was a time of plains, rivers and lakes, the verdant surroundings of the latter rivaling the Louisiana country of the present day.

Along with the sequoias were many hardwood trees—oaks and maples, hickory and ash; alligators pushed their way through the sedges; the cypress and palmetto grew in Montana, Colorado and Greenland. Stately palms furnished shade for primitive rhinoceroses, tapirs and camels. Monkeys swung from branch to branch and gathered the fruits, where to-day there is nothing but the barren wastes of the alkali 'bad-lands.'

The next period, the Miocene, witnessed the zenith of sequoia development. Contemporaneous with the tapirs, rhinoceroses, horses and