Page:Popular Science Monthly Volume 83.djvu/120

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 a, b, spectra of two sun-spots. The triple line indicates a magnetic field of 4,500 gausses in a, and one of 2,000 gausses in b.

opposite components of a magnetic double line should appear in two such spots. As our photographs show, the result of the test was in harmony with my anticipation.

I may not pause to describe the later developments of this investigation, though two or three points must be mentioned. The intensity of the magnetic field in sun-spots is sometimes as high as 4,500 gausses, or nine thousand times the intensity of the earth's field. In passing upward from the sun's surface, the magnetic intensity decreases very

 indicated by the distribution of hydrogen (Hα) gas. photographed with the spectroheliograph.