716 BIRKELAND. THE NORWEGIAN AURORA POLARIS EXPEDITION, igO2 1903. 



my assumption of a sun-moment of an order io l0 C.G. S. and opposite to that of the earth, an estimate will 

 easily show that the induced electromotive force in space about the sun will not be so great as about 

 the earth, and its direction will be from the equator to the poles. There will then, of course, be no 

 question of explaining the great discharges from the sun, in which the tension goes up to 600 million 

 volts p) (see p. 665), as an induction-phenomenon of this kind. The most reasonable hypothesis therefore 

 seems to be that the sun and the stars are negative all over in relation to surrounding space. 



It is otherwise if we calculate with SCHUSTER'S purely hypothetical value for the intensity of 440 

 times the intensity on the earth. We should then most probably come to an electromotive force of about 

 2 milliard volts, acting from the poles to the equatorial regions, which would thus have to be regarded 

 as the cathode in the eventually produced discharges, while the poles were anodes. 



138. It is a circumstance in my planet-theory which has given me much trouble, as it looked at 

 first as though the planets, if formed, would come to revolve the wrong way round the central l> 

 I considered it at first most probable that the material particles expelled by disintegration from the 

 negative-electric central body, took with them a negative charge. 



It was soon evident, however, that if, for instance, the magnetisation of the sun as I have had to 

 assume is the reverse of that of the earth, the negatively-charged particles would hardly be able to 

 approach the boundary-circles in the same way as the planets move in their orbits. At any rate they 

 must first change from out-going to in-going motion, and be subjected to a suitable resistance. For one thing 

 this resistance must be such that the velocity, in spite of gravitation, would be diminished during the 

 in-going motion, and it seems physically unreasonable to assume the existence of such a resistance. It 

 would be far easier for the particles to approach the boundary-circles the opposite way. It therefore 

 appeared probable from the theory, that we should be compelled to assume that the expelled particles 

 would, partially at any rate, be positive. 



This led me to think that possibly the electric disintegration from a cathode had some poin: 

 resemblance to the disintegration of radio-active substances, which emit a-particles, even if the emitting 

 substance is charged negatively. 



It occurred to me, moreover, that since it has been decided that the particles in AVrays emitted 

 by a cathode, are positively charged, it might be well worth finding out whether the material particle 

 expelled by disintegration also carried a positive charge. 



By examining the literature on the subject, I soon saw that there were no definite results that 

 could decide the question, although our idea of the constitution of matter presupposes that the atoms in a 

 non-electric piece of metal are positively charged, and that there are corresponding free negative 

 Irons between the molecules. From a theoretical point of view it might thus be conceivable that the 

 atoms ejected from a cathode were positively charged. 



It was for this reason that I commenced these investigations of the disintegration of cathodes, some 

 of which have been described in the Article on Saturn's Ring, while others will now be described. 



As mentioned on p. 659, my attention, while experimenting on the disintegration of the cathode, 

 was increasingly drawn to the more or less normally expelled particles which formed an evenly 

 reflecting deposit of palladium on the cylindrical glass wall of the vacuum-tube, right round the cathode 

 A number of experiments were therefore made by introducing little, flat screens of mica, with or with 

 a slit, at various distances from the cathode. The palladium cathode was in the form of a long rectangle 

 whose long centre line coincided with the axis of the tube. It appeared, however, that notvvithstandin 



(') In my experiments with an electric corona I use from o. i to 0.2 milliamperes per sq. cm. of the surface of the globe-ca 

 If we suppose a similar value of the current from the sun, and the tension to be 600 million volts, this correspon 

 about too kw. per cm. Such an energy would easily account for all heat and light radiation from the sun. 



