672 Prof. F. A. Lindemann on the 



their velocity to be that o£ ThC rays, the fastest known, viz. 

 2*22. 10 9 cm./sec. This corresponds to an energy 1*53. 10 -5 

 erg, so that the a ray could only strike the earth even if 



aimed at it in the best possible way if - 1 — < — — or 



J a 2 



Ei<5*2-.10 12 , E x being the earth's charge and a its effective 



radius. The value calculated by Dr. Chapman is 3.10 16 , 



i. e. 6000 times greater. 



It need scarcely be added that these objections hold with 

 additional force if {3 rays are assumed on account of their 

 smaller mass. It would appear, therefore, that existing 

 stream theories of magnetic storms are untenable and must 

 be replaced by some modified form. 



Since the storms are undoubtedly due to solar phenomena 

 there are apparently only two alternatives, namely, that the 

 influence is electromagnetic, or that some corpuscular radia- 

 tion intervenes. Ordinary induction effects are obviously 

 impossible. Electromagnetic radiations can only ionize a 

 gas and separate the charges a distance of the order of the 

 tree path of an ion in the gas. This would increase the 

 electrical conductivity, but Dr. Chapman has given reasons 

 for believing that this would not explain the observed 

 magnetic phenomena. One must therefore consider how 

 the energy of a magnetic storm, of the order U = 10 23 ergs, 

 could be transmitted by corpuscular radiations. 



It is clear that charges of one sign are not sufficient, 



c • -i i i. x- v < a wl ' 2 -i.i mv ' 2 



lor since the charge at any one time E.^ -. — , either - - 



° - — 2ne 2 



must be enormous, which could only be explained by 

 assuming a radioactive substance of very short life, or E t 

 must be small. If Ej : : s small the total charge E must be 



large, for U= * E, which cannot exceed —J — . If E is 

 rt ' a 2 2a 



large the number of particles emitted per second must 



be large, and the mutual repulsion would render anything 



of the nature of a beam impossible. 



Therefore approximately an equal number of positive and 



negative charges must strike the earth. If U = I0 23 ergs is the 



energy of the storm it is clear that X, the number of particles 



2U 



striking the earth, is - — r,. If v is so great that the time of 



transit from the sun is short compared with the duration of 

 the storm, the radius of the beam must be of the order 



