﻿2?>2 Mr. L. Vegard on the Properties of 



the same source, the one band must at any moment be equi- 

 distant with the orher, it would appear as it' the bands in a 

 mysterious way were attached to each other. Indeed, such a 

 motion is most characteristic, and often observed for a system 

 of parallel auroral bauds. 



If we did not know the radioactive processes, it would 

 indeed seem a rather artificial explanation, which was built 

 on the assumption of a mixture of homogeneous rays given 

 out from the same source; for any kind of electric discharge 

 producing such conditions is almost inconceivable. On the 

 other hand, when we assume a kind of a-radiation to produce 

 the bands such conditions are not only conceivable, but may 

 rather be considered a necessary consequence, because a 

 number of radioactive compounds intimately mixed, each pro- 

 ducing its own homogeneous a-radiation, will be formed by 

 atomic disintegration of some parent substance. 



In this connexion it may be w r ell to remember that any 

 homogeneous radiation would have to start from the sun in 

 such a way that the rays were able to pass into space without 

 traversing any appreciable layers of matter, and if radioactive 

 substances formed the source, they would have to exist in 

 very thin layers. A radioactive emanation ejected from the 

 sun and disintegrating w r ould fulfil all necessary conditions. 



From our point of view the drapery bands should give a 

 kind of magnetic spectrum of the homogeneous groups of 

 a-rays present in the source, and as the a-rays are charac- 

 terise of the substances emitting them, a possibility opens 

 out of studying or identifying the family of radioactive 

 substances present in the sun by observing the relative 

 distances between the various bands. 



If we adopt the simplified system of an elementary magnet 

 we may, from a formula given by Stormer, calculate the 

 position of the bands caused by a-rays from a certain family 

 of radioactive substances. 



Let (o denote the angle between the magnetic axis and a 

 line from the earth's centre to the band, and let D be the 

 distance from the centre of the earth to the bottom edge of 

 the band, then 



/o D 1 / * 



= \/ 2 ?1 - 5 Wllere C =\' J} 



M 



no) = \/ 2y 1 , where c=\/ — 



For the draperies to be formed 7! must be between 0*9 and 1. 



A change of co corresponding to a change of deflectibility. is 



found from the relation 



Ac 

 Aco= — J tan (o — . 



