﻿220 



Mr. L. Vegard on the Properties of 



In dealing with the auroral problem I think we ought to 

 be aware of the possibility that not all the luminous phenomena 

 called northern lights are necessarily produced exactly in 

 the same way and by the same agencies. Consequently, the 

 diurnal variation may be different for different forms, and 

 ©right to be found for each type separately. 



The types which mostly interest us in connexion with the 

 a-ray theory are those which we might call radiant forms, 

 containing all types of aurora showing definite streamers 

 ending suddenly with a maximum of luminosity. To this 



Fig. 4. 



Winter 1882-83 



-. 



16 



4 



.. _.. — T .... _, — T — r ,,..,_ ... 



Corona 1 \ • 



Radiajit forms • >■ 



/ -A 7 ^>i: 



<** ' ~~ 1 



-^ 



i 



Corona. 



Vrajicj-ics \ 



A ' 

 / \ '^ 





1 



i' 

 * 



Corona. 



J>rajici-U'^ 



- 1 



1 



« 





Corona. 



Rai/s • , 



,'' " ~^ 



^l^X^j 



O^'' ^-- // " 





In Zcnitlv 



Ciu-tain shajied J 



1— , , li- — -^>- ■■■ « 



12 

 ni /n 



— - — Magnetic Tiu'dttioht 



group belong, e. g., the draperies, the corona, rays and ray- 

 bundles, a number of auroral bands, and probably some of 

 the forms put down, as arches may be merely distant aurora 

 belonging to this group. 



