286 Mr. H. F. Neivall [Feb. 9, 



of this is sufficient to prevent the negative ions from getting right 

 away from the sun ; and yet, even in this case, if the temperature 

 were for any cause to rise above its average value, corpuscles would 

 stream away from the sun into the surrounding space. Such cor- 

 puscles going out from incandescent bodies will produce luminosity 

 in gases round about the sun's surface." Thomson and Arrhenius 

 have boldly suggested that the Aurora Borealis is produced by such 

 corpuscles in the outer part of our atmosphere. 



It has been also shown that not only are negatively charged 

 corpuscles emitted at very high temperatures, but also positively 

 charged ions at lower temperatures. 



One point more I should like to mention, and that relates to the 

 phenomena of magnetism on the surface of the earth. In the last 

 few years the relation between spots on the sun and magnetic storms 

 on the earth has been very much studied, and in one of the latest 

 contributions on the subject — that of Mr. Maunder, of the Royal 

 Observatory, Greenwich — the author has been led to the view that, 

 in the occurrence of notable storms recorded by magnetic instru- 

 ments, he has found a tendency for storms to recur at intervals equal 

 to that of the rotation of the sun, viz. about 27 days ; and he points 

 out that the meaning of this may be that certain regions of the sun 

 are emitting something which, in their recurrent presentation towards 

 the earth, gives rise to recurrent magnetic storms. 



The idea is, that from such regions something is emitted which, 

 arriving at the outer confines of the earth's atmosphere, somehow 

 results in magnetic storms. I will not go further into the mechanism 

 by which these storms are produced on earth, or by which we get the 

 enormous quantities of energy which are involved in them, than to 

 say that there is a strong consensus of opinion that the energy which 

 is evidenced in the storm is derived from the energy of rotation of 

 the earth. Something arrives or something happens in the outer 

 atmosphere, and there actions take place w^hich convert some of the 

 energy of the rotation of the earth into the form of magnetic 

 manifestations. 



Even if one has to confess to a certain human weakness of will to 

 keep oneself convinced of the reality of this periodic recurrence — and 

 I confess I feel on some days that I am convinced by the evidence, 

 and on other days that I am not convinced — in spite of the material 

 with which Mr. Maunder has supported his views, and in spite of the 

 support which Professor Schuster and Mr. Dyson have given to the 

 discussion of the evidence, there still survives the indubiUible fact 

 that the eleven years' cycle of the sun is accompanied by changes in 

 magnetic phenomena in the earth. 



Now, among tlie seeds which I have sown, we have dust and 

 vapour round the sun. We have high temperatures just at the places 

 where high velocities are ; we have splintered fragments ; we have 

 light pressure ; we have corpuscles producing luminosity in the 



