170 ANNUAL. REPORT SMITHSONIAN INSTITUTION, 1923 



one appearance. If the single appearances in figure 7 had been 

 omitted, the resemblance between the two diagrams would have been 

 much increased. In other words, the intervals between the successive 

 returns of a group of spots to the center of the sun's disk, as seen 

 from the earth, are strictly comparable with the intervals between 

 the recurrences of a magnetic storm. Magnetic storms obey the law 

 of the sun's rotation. 



Distribution 0/ MAGNETIC STORMS, 1862 t» 1866, 

 for each Rotation of tJvt Sun. 



I I I I I I I I I I I I I I I I I I I I I M I I I I I I I 



n 



309 I no' zio' I iso' no' I 60 3d 

 H6 no' wtf 90° ' 



\8&l • • • 1**3 



Ittt •— I86v 



1865 • • w _ W6S 



1866 Hit 



9 • #- 



• — • 



Nofc.Tke iot, mlitat* Hi* Htl.-oyrapii.c lonjitud. of A* Ctntrt c' r rt« Sun* D.'<c a.t tkt tim*. 

 of the toiKmin-ct-mtnt ef- *oxh of t\i Maomtit Stormt. 



Fig. 7 



This could not be so if the influence that brings about our magnetic 

 storms proceeded equally from every part of the solar surface and 

 was radiated from it equally in all directions. It follows that mag- 

 netic storms are brought about by an influence which arises from 

 restricted areas of the sun's surface, and is discharged from such areas 

 in restricted directions. Thus Mr. Gavin Burns has tabulated his 

 records of aurorse (Memoirs of the British Astronomical Association, 

 23, Part I., "Eeport of the section for the observation of aurorse 

 and the zodiacal light, 1916-1919") in recent years in accordance 



