io6 THE POPULAR SCIENCE MONTHLY 



Fig 1. DiuECT I'hotoohai'ii of the Sun with Dot kkpresenting 

 Earth fok Compakison. 



has been rotating for centuries at high velocity. The sun, with a diam- 

 eter one hundred times that of the earth (Fig.l), may throw some light 

 on the problem. Its high temperature wholly precludes the existence of 

 permanent magnets : hence any magnetism it may exhibit must be due 

 to motion. Its great mass and rapid linear velocity of rotation should 

 produce a magnetic field much stronger than that of the earth. Finally, 

 the presence in its atmosphere of glowing gases, and the well-known 

 effect of magnetism on light, should enable us to explore its magnetic 

 field even at the distance of the earth. The effects of ionization, prob- 

 al)ly small in the region of high pressure beneath the photosphere and 

 marked in the solar atmosphere, must be determined and allowed for. 

 But with this important limitation, the sun may be used by the pliysi- 

 cist for an experiment which can not be perforniod in the best equipped 

 laboratory. 



Schuster, in the lecture ah'oady cited, rcnuirked: 



The form of the coroiia suggests a further hypothesis which, extravagant 



