190 Trowbridge — Magnetic Field and Coronal Streamers. 



walls of the tube and the necessary obliquity in the reflection 

 modify the sharpness of the image. The speed of revolution 

 increases with the degree of exhaustion of the raritied air. 

 When the free path of the ions increases, the progressive effect 

 along the magnetic lines becomes more than the rotational 

 effect of the magnetic field. When the plate forms the anode 

 and also the end of a magnetic pole the lines of magnetic force 

 being directed along the line of electric discharge, the light 

 at the anode is separated into two distinctly different lights ; 

 one (in raritied air), a plume-like rosy light, the other a plume- 

 like violet light. These discharges also revolve around the 

 pole near the center of the disc instead of on the circum- 



ference, as in the case of the cathode disc. On account of the 

 number of individual discharges on the anode it is difficult to 

 follow their motions in a revolving mirror or by the eye, 

 or to photograph them. It is certain, however, that they 

 revolve about the pole. 



The unipolar rotation which I have described leads my 

 mind to connect the jmenomenon of coronal streamers seen at 

 the poles of the sun in an eclipse, with the effect of a magnetic 

 field on possible electrical discharges between the equatorial 

 regions of the sun and the poles of the sun. If we suppose 

 that a difference of electrical potential can arise between the 

 swiftly moving strata of gases or from the eruptions which 

 take place mainly along the equatorial belt and the polar 

 regions, the supposed magnetic poles of the sun would undoubt- 

 edly tend to cause the resulting electric discharges to revolve 

 about the pole. On account of the vast circumferential area 

 about the poles a number of discharges could occur at different 

 points around the pole and each discharge would revolve under 

 the effect of the pole. In observing the effect of a strong mag- 

 netic pole on plate terminals in wide tubes of raritied air, at 

 comparatively high pressure of air under conditions of high 



