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THE POPULAR SCIENCE MONTHLY 



whirl of ions in a tornado produces a magnetic field, it is too feeble to be 

 readily detected. Thus, while we have demonstrated the existence of 

 solar magnetism, it is confined to limited areas. We must look further 

 if we would throw new light on the theory of the magnetic properties 

 of rotating bodies. 



This leads us to the question with which we started : is the sun a magnet 

 like the earth ? The structure of the corona, as revealed at total eclipses, 

 points strongly in this direction. Eemembering the lines of force of 

 our magnetized steel sphere, we can not fail to be struck by their close 

 resemblance to the polar streamers in these beautiful photographs of the 

 corona (Fig. 12) taken by Lick Observatory eclipse parties, for which 



Fig. 12. Solar Corona, showing Polar Streamers. 



I am indebted to Professor Campbell. Bigelow, in 1889, investigated 

 this coronal structure, and showed that it is very similar to the lines of 

 force of a spherical magnet. Stormer, guided by his own researches on 

 the aurora, has calculated the trajectories of electrons moving out from 

 the sun under the influence of a general magnetic field, and compared 

 these trajectories with the coronal streamers. The resemblance is 

 apparently too close to be the result of chance. Finally, Deslandres has 

 investigated the forms and motions of solar prominences, which he 

 finds to behave as they would in a magnetic field of intensity about one 

 millionth that of the earth. We may thus infer the existence of a gen- 

 eral solar magnetic field. But since the sign of the charge of the out- 

 flowing electrons is not certainly known, we can not determine the 

 polarity of the sun in this way. Fuithermore, our present uncertainty 



