254 Bigelow — Magnetic Theory of the Solar Corona. 



foil and containing gas in a rarefied state, through which elec- 

 tric oscillating currents were made to pass. The electric 

 discharge rays as formed by experiment bore a strong resem- 

 blance to the visible coronal rays, in regard to mutual repul- 

 sion, helical rolling of the individual streamers, color and 

 instability, so that there was strong presumption in favor of 

 pursuing this analogue to its conclusion. However, Lord 

 Kelvin's presidential address* on. "The Sun's Effect on Terres- 

 trial Magnetism," came to the discouraging conclusion that the 

 work required to be done by the sun to produce the observed 

 terrestrial effects was too excessive to be considered practicable, 

 and this brought the subject to a standstill in the minds of 

 many for want of a convenient answer to this disconcerting 

 result. But continued researches by Bigelowf and EllisJ on 

 the sun spots and the terrestrial magnetic field, have demon- 

 strated that Lord Kelvin's view cannot be maintained, and 

 that there is in fact a continuous contact between the solar 

 and terrestrial forces. It may be remarked in passing that the 

 application of the formula for energy, from which the work 

 expended was computed, namely, 



fails to take any account of secondary effects. Thus the solar 

 forces may set in operation such processes as ionization, which 

 modifies the magnetic field in the earth's atmosphere in pro- 

 portion to some other factor than unity. The physics of the 

 case is evidently too complex to be solved in so simple a man- 

 ner as the above, and in the face of the well known continuous 

 and unmistakable testimony of the observations it cannot be 

 accepted as a barrier to further investigation. 



The critical experiment has fortunately been made by H. 

 Ebert§ which goes far to clear up the entire subject and put 

 the theory on a working basis. I have made the following 

 translation of his note : " For the explanation of the most 

 important characteristics of the polar light phenomena, the 

 following experiments were made : Spheres, disks and cylin- 

 ders of iron and brass were exposed to the action of electro- 

 magnetic oscillations in spaces filled with rarefied gases ; by 

 this means their surroundings were made to glow, and the 

 bodies mentioned were clothed with envelopes of light having 

 a ray structure, whose color and appearance was different 



* Nature, Dec. 1, 1892; Astrophysics, Jan., 1893. 



\ Bulletin No. 21, 1898; 



\ Proc. Roy. Soc, vol. lxiii. 



§ Yersammlung deutscher Naturforscher u. Aerzte zu Liibeck, 1895 



