160 



HIKKKI.AMl. I UK NOKWIJ.IAN ATKOKA 1'OI.AKIS KXrl.DI'l IOX, TgO2 -1903. 



"As regards the angle M( ).\, much will depend upon the stiffness of the 

 rays (see mv paper, ^ 17); will) constant stiffness, however, point \ will 

 approach M when t/i increases. Before tnrther data can he obtained lor the 

 stillness of the ravs that cause aurora and magnetic perturbations, we mav 

 assume, in accordance with the observations, that X is situated in the auroral 

 zones. 



"The appearance and disappearance of the various districts of precipita- 

 tion, and their movements along the north and south auroral /ones, according 



" o 



as the altitude (/; of the sun above the magnetic equatorial plane changes with 

 time, can then he calculated hv the above. We shall return to this subject in 

 a later section ot this work." 



V * 





Fig. 76. 



