Page:Popular Science Monthly Volume 27.djvu/396

380 this question. Formerly there was a warm climate in the north during the Tertiary period. This was a certain measurable time ago, when the circumpolar regions had a warm average temperature, with no winter, and the moths of the period were then substantially the same species from Norway across Siberia to Greenland. During this happy time—happy, at least, so far as weather was concerned—we must imagine that no impediment existed to the migrations of animals across what is now Behring Strait. It is probable, even, that the Tertiary epoch, as it witnessed the first appearance of man, saw his first wanderings in North America. He, too, came from Asia by way of the north and Behring Strait. Evolution had performed surprising work in the mean while with one branch of the human family, members of which, landing from Scandinavian or Spanish ships, met, upon American soil, the descendants of a migration from Asia to America in a former geological period, and to the east! At the close of this Tertiary period of the earth's history, cold and snow and ice set in; the long winter of the ages made its appearance in the shape of the Glacial epoch. The circumpolar moths, whose more humble fortunes we must be content here alone to follow, were forced southward gradually by the change in climate which gathered its frigid strength in the north. The European, Asiatic, and American faunæ then became separated, the latter the most completely, and by barriers both of ice and ocean. The American species of moths, which formerly lived upon the shores of the Arctic Ocean, were gradually forced down, year by year, until they reached Mexico, or the elevated portions of the Southern States. When the glaciers subsided, and the floods of ice which had submerged the continents gradually melted and slowly drained away, the moths, much changed by the long conflict, also retraced their steps northward. As marks of the retreat and advance, colonies of moths were left on the mountains to tell of the flood. At this time our "Western clawed cutworm" (Copimamestra occidenta) had been long separated from its present European brothers, and the differences by which we now recognize the two species as distinct had become slowly established through a long series of succeeding generations. What miles of land and sea separate the two to-day! The descendants of a common circumpolar species find themselves partly in Germany, partly in Arizona, and the Southwestern territory of the United States!

Let us turn back to the other theory, that of a submerged Atlantic Continent. Whatever may be finally proved from geology as to the existence of such an Atlantic bridge, it is clear that the myth of the Atlantis must be separated from such facts, as being of much more recent origin. Primitive man existed æons before the notions which were worked into the poetic and semi-historical myth of the Hesperides and Atlantides. The setting sun was followed by human eyes for untold ages, as it bathed itself in the golden flush of evening, and was