. Popular science monthly. experiment which can not be performed in the best equippedlaboratory. Schuster, in the lecture already cited, remarked: The form of the corona suggests a further hypothesis which, extravagant THE EARTH AND SUN AS MAGNETS 107 as it may appear at present, may yet prove to be true. Is the sun a magnet? Summing up the situation in April, 1912, he repeated: The evidence (whether the sun is a magnet) rests entirely on the form ofcertain rays of the corona, which—assuming that they indicate the path ofprojecting particles—seem to be deflected as they would be in a magnetic
. Popular science monthly. experiment which can not be performed in the best equippedlaboratory. Schuster, in the lecture already cited, remarked: The form of the corona suggests a further hypothesis which, extravagant THE EARTH AND SUN AS MAGNETS 107 as it may appear at present, may yet prove to be true. Is the sun a magnet? Summing up the situation in April, 1912, he repeated: The evidence (whether the sun is a magnet) rests entirely on the form ofcertain rays of the corona, which—assuming that they indicate the path ofprojecting particles—seem to be deflected as they would be in a magnetic field,but this evidence is not at all decisive. There remained the possibility of an appeal to a conclusive test ofmagnetism: the characteristic changes it produces in light which orig-inates in a magnetic field. Before describing how this test has been applied, let us rapidly re-capitulate some of the principal facts of terrestrial magnetism. You seeupon the screen the image of a steel sphere (Fig. 2), which has been. Fig. 2. Lines of Foecb of a Magnetized Steel Sphere. strongly magnetized. If iron filings are sprinkled over the glass platethat supports it, each minute particle becomes a magnet under the influ-ence of the sphere. When the plate is tapped, to relieve the friction, theparticles fall into place along the lines of force, revealing a characteristicpattern of great beauty. A small compass needle, moved about thesphere, always turns so as to point along the lines of force. At themagnetic poles, it points toward the center of the sphere. Midway be-tween them, at the equator, it is parallel to the diameter joining thepoles. As the earth is a magnet, it should exhibit lines of force resemblingthose of the sphere. If the magnetic poles coincided with the poles ofrotation, a freely suspended magnetic needle should point vertically io8 THE POPULAR SCIENCE MONTHLY
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