"Every reader of this book has heard of the Aurora Borealis, or Northern Lights, and the Aurora Australis, or Southern Lights. Some readers may have visited Norway and gone far enough to catch a glimpse of this mysterious phenomenon. We say mysterious because scientists have never been able to explain it, although they usually try to do so by saying something indefinite about the earth's electricity and magnetism. We claim, on the basis of our theory, to explain definitely what causes the auroral lights: that the central sun, flashing its beams through the polar openings, is the cause. To enforce this claim we shall first describe. in the words of competent observers, just what these lights look like and how they behave. We shall then show--also on the best scientific evidence--that they are not and could not be caused by electricity or magnetism; we shall refute many fallacies on that subject. And then we shall give abundant evidence proving that the reflection of the rays of the central sun by the earth's atmosphere, modified by the conditions, cloudy or otherwise, of the atmosphere of the interior of the earth, is what causes these wonderful displays of light..."
Excerpted from: Chapter XIV - "The Aurora" - A Journey to the Earth's Interior [1920] by Marshall B. Gardner
