. Popular science monthly. irled in the spot vortex,should produce a magnetic field. Fortunately, this could be put to aconclusive test, through the well-known influence of magnetism on lightdiscovered by Zeeman in 1896. In Zeemans experiment a flame containing sodium vapor was placedbetween the poles of a powerful electro-magnet. The two yellow sodiumlines, observed with a spectroscope of high dispersion, were seen to widenthe instant a magnetic field was produced by passing a current throughthe coils of the magnet. It was subsequently found that most of thelines of the spectrum, which are si
. Popular science monthly. irled in the spot vortex,should produce a magnetic field. Fortunately, this could be put to aconclusive test, through the well-known influence of magnetism on lightdiscovered by Zeeman in 1896. In Zeemans experiment a flame containing sodium vapor was placedbetween the poles of a powerful electro-magnet. The two yellow sodiumlines, observed with a spectroscope of high dispersion, were seen to widenthe instant a magnetic field was produced by passing a current throughthe coils of the magnet. It was subsequently found that most of thelines of the spectrum, which are single under ordinaly conditions, aresplit into three components when the radiating source is in a sufficientlyintense magnetic field. This is the case when the observation is madeat right angles to the lines of force. When looking along the lines offorce, the central line of such a triplet disappears (Fig. 9), and the lightof the two side components is found to be circularly polarized in oppo- THE EARTH AND SUN AS MAGNETS 5. Fig. 9. Zee man Doublet photographed in Laboratory Spectrum. The middlesection shows the doublet. The adjacent sections indicate the appearance of thespectrum line in the absence of a magnetic field. site directions. With suitable polarizing apparatus, either component ofsuch a line can be cut off at will, leaving the other unchanged. Further-more, a double line having these characteristic properties can be pro-duced only by a magnetic field. Thus it becomes a simple matter todetect a magnetic field, at any distance, by observing its effect on lightemitted within the field. If a sun-spot is an electric vortex, and theobserver is supposed to look along the axis of the whirling vapor, whichwould correspond with the direction of the lines of force, he should findthe spectrum lines double, and be able to cut off either component withthe polarizing attachment of his spectroscope. I applied this test to sun-spots on Mount Wilson in June, 1908,with the 60-foot towe
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