458 F. H. Bigelow — Solar and Terrestrial Magnetism. 



The third line of argument tending to show that the sun 

 though hot is magnetic is found in the compilation of testi- 

 mony contained in Chapter 6. There it is shown that the rifts 

 seen in coronas of the sun during eclipses closely tit the struc- 

 ture of a spherical magnet whose lines are viewed in projection 

 on a plane, and we need only to suppose that the magnetic 

 lines of the sun tend to arrange the surrounding material of 

 its envelopes in the same way that a steel magnet disposes iron 

 filings in its neighborhood. The period of rotation for an 

 assumed solar nucleus is such that at least three coronas seem 

 to correspond to one and the same model, when located 

 mechanically by astronomical coordinates. The distribution of 

 the sun spots in the adopted period of 26*68 days, in the two 

 hemispheres, gives back the characteristic type curve, in its 

 direct and inverse forms, pointing at least to some subtle and 

 perhaps unsuspected law of solar operation. The Chandler 

 long period variation of the position of the earth's axis of rota- 

 tion is in so close agreement with the well known 11-year sun 

 spot period as to demand complete investigation. Finally, the 

 peculiar phenomenon of inversion of the type curve semi- 

 annually in all its characteristics, constitutes another delicate 

 test of the general fact of the magnetization of the sun, since 

 its turning points are precisely in harmony with the position 

 of the sun's axis and nodes, so that an accidental coincidence is 

 quite impossible. Such a long series of phenomena, as those 

 just enumerated, if not proving that the sun is a magnet, at 

 least demands the respectful attention of those who still adhere 

 to the high temperature argument. 



Electric currents in the cirrus region. — It is probable that 

 the only real strength behind the hypothesis, that a system of 

 electric currents in the cirrus level is the cause of the varia- 

 tions of the earth's magnetic field as observed at the surface, 

 is due to the process of exclusion by which the direct action 

 of the sun as a magnet, the Faraday idea of the magnetic 

 action of the oxygen of the atmosphere under differences of 

 heat, and also the thermoelectric currents of the ground, were 

 thrown out of the discussion. Passing over the last two 

 entirely, it is quite clear that insuperable difficulties stand 

 against the electric current theory. These are supposed to 

 originate in the general motions of the atmosphere, due pri- 

 marily to convection over the hemisphere, and hence they 

 depend upon meteorological phenomena. But why assign 

 them to the cirrus region, except on the philosopher's plan of 

 always keeping the causes just beyond reach of criticism. In 

 fact the cirrus region is known to be about the best behaved 

 stratum in the atmosphere, since it is entirely exempt from all 

 the minor variations of temperature felt near the ground ; 



