498 



Prof. S. Arrhenius. 



[June 2, 



If the sun only emitted negatively electrified particles on all sides, it 

 would soon assume so great an electric charge of positive sign, that 

 the electric forces would hold the negative particles back in the 

 neighbourhood of the sun. There must, therefore, be some cause that 

 carries back as much negative electricity to the sun as it loses through 

 the emission of negative particles. In supposing the least negative 

 charge to be the same as the positive one of a hydrogen atom, 

 weighing 8 x 10~ 25 grammes, it may be calculated that the force with 

 which this is drawn back to the sun by a potential slope of 

 3000 volt per cm., amounts to 23*2 dynes. A drop of radius 0'08 /x, 

 of the specific weight of water, has the weight 59 x 10~ 10 dynes at the 

 surface of the sun. Its repulsion by the pressure of radiation is about 

 2 '5 times greater, 148 x 10~ 10 dynes. The electric attraction is there- 

 fore only about the fourth part of the total force by which the drop is 

 driven away from the sun ; therefore its speed is only three-fourths of 

 that calculated before. It is evident that if the electric charge of the 

 sun, or rather of its upper atmosphere, is much greater (about four 

 times) than that supposed, no negatively charged particles can be 

 emitted from the sun. On the other hand, if the sun's charge is less, 

 the particles will move with a speed that is nearly independent of 

 the magnitude of the charge. Probably the charge of the sun in times 

 of great emission, i.e., at sun-spot maxima, will be of this order of mag- 

 nitude, and in times of sun-spot minima somewhat less. 



The charged particles are driven out to all sides from the sun. It 

 might, perhaps, be expected that they would lose their electric 

 charge under the influence of the strong ultra-violet radiation from 

 the sun. But the circumstances must be other for these small particles 

 than for great pieces that are examined in our laboratories. Otherwise 

 it would be impossible to conceive that drops are condensed at all on 

 the negatively charged electrons under the influence of ultra-violet 

 light* 



But if many drops agglomerate together, the potential increases and 

 greater pieces are formed, which can lose their charge gradually. 

 According to the experiments of Elster and Geitel, and Lenard, these 

 charged bodies part slowly with their negative charge in the form of 

 electrons that traverse space. 



The path of these electrons is now influenced by the strongly 

 positively charged suns. Their paths become by this influence curved, 

 and they describe hyperbolas round the suns. If their perihelial 

 distance is less than the sun's radius, they fall down on the sun, and 

 diminish its positive charge. 



If we now suppose the electric charge of the sun to be just as great 



* As the first drops contain only one elementary charge of electricity, they 

 would lose their whole charge at once at a discharge. Perhaps this circumstance 

 causes the difference for elementary and great charges. 



