Page:Popular Science Monthly Volume 78.djvu/31

Rh nature analogous to that of a resisting gas. In fact, as the meteors are burned up, we must acknowledge that the debris are perpetually making new additions to our atmosphere. So important is this question, both to astronomy and to meteorology, that the Astronomical and Astrophysical Society of America has lately started an inquiry as to what methods are available for photographing meteors and meteor trains, or what studies can give us any facts about the highest air. I understand Professor Woodward to state that there is a mechanical possibility of the existence of another atmosphere above that which affects our barometer, which therefore may revolve about the globe, like the rings of Saturn, in equilibrium within itself.

The most interesting definite problem bearing on the highest atmosphere relates to the cause and nature of the aurora borealis. These beautiful northern lights have been carefully studied by Swedes and Norwegians. Twenty years ago, all the nations of the globe united in a series of expeditions to both the arctic and antarctic regions for the study of magnetism, auroras and meteorology. Since that date four special expeditions have been sent northward by Norwegians, and the leader of these. Professor Birkeland, of Christiania, has developed some new views as to the aurora, that have been confirmed by the mathematical investigations of his colleague. Professor Stoermer. They have devised remarkable ways of continuous photography and accurate calculation of altitudes. The publication of the details of their work has begun, and I think we may safely anticipate that future generations will busy themselves developing the ideas that are now being presented by these physicists. All that we need say at the present moment is that particles which we call ions (or, when they are electrified, electrons), pass with the velocity of light from the sun to the earth. If this be incredible, we must at least say that some influence passes from the sun to the earth, with the speed of gravity or the speed of light, causing electrons from space or from the celestial bodies to approach the earth's atmosphere with great speed. But no sooner do these come within the influence of the earth's magnetism (and that influence extends to great distances beyond the atmosphere), no sooner do the electrons feel this influence, than they are diverted from their straight-line courses and begin to describe curves surrounding the earth like spiral corkscrews. Whenever such particles enter certain gases (such as krypton), the gas becomes luminescent or phosphorescent, and gives us the auroral light. This hypothesis is sufficiently complex to allow of many uncertainties as to details. It is at present in its formative stage, but there is good reason to believe that we have here a solid base on which to build a structure that will carry us from the firm ground of experimental laboratory physics over into the equally firm, but unexplored region of mathematical cosmical physics.