Page:Popular Science Monthly Volume 51.djvu/654

638 under the masses of ice we discover remains of plants that demonstrate the presence not so very long ago of a flourishing tropical or subtropical vegetation instead of the present ice. We meet mountains of ice everywhere, and everywhere the arctic region is sublime. Man's disposition to make all the earth his home and himself at home everywhere in it is only sharpened by the problems offered there, and the tendency to go becomes irresistible.

There is thus much to observe and much to learn in these regions for the satisfaction of our irresistible longings. First, we are able to study in the polar regions the division of land and sea, the size, elevation, and topography of the land—the whole question, in short, of polar geography. The form of the earth's surface is not casual, but is the result of interactions of the crust and the interior of the globe. The discovery by Nansen's expedition of the profundity of the polar sea tallies with Prof. Mohn's observations of the great depths between Greenland and Spitzbergen and with those of the fiords and interinsular channels of the North Atlantic. Further, the sea bottoms are penetrated by volcanoes, some of them still active—here single, as in Jan Mayen Island, there in groups, as in Franz-Joseph Land and Fire Island. A marked difference exists in this respect between the Atlantic half of the polar regions north of Europe and eastern North America, where disturbance and divisions of the land are the rule, and the Pacific side, north of Siberia and western America, where quiet prevails, with regular coast forms and few islands. The lands on the Atlantic side have, moreover, been gradually rising for an in-calculable length of time, and are still rising, while those on the opposite side have until very recently been subsiding. These facts, selected as examples from a great number of phenomena, may serve to illustrate how important is a knowledge of the polar regions to that of the earth as a whole. Its importance is, in fact, quite beyond comprehension.

So the magnetism of the earth, the colored beams of the northern lights, the flickering of their draperies and bands, are of interest far beyond their relations to the earth alone; for the movement of the magnetic elements reflects the processes of the sun's atmosphere, and may be connected with the immense periods of the revolution of our solar system. Man could not refrain from inquiring into the nature and reason of these things even if he would, and hence he is willingly or unwillingly led to the poles, where he is brought into the closest relations with them, and where the explanation of them can be most hopefully sought.

A relation between the northern lights and the weather has been established by repeated observations, and that brings us to