Tlie Moition and l)intiihution of the Sun-spots 



13 



latitude-drift oE the spots, it seems as if there existed a nortlierly drift, a little 

 greater on the northern than on the southern hemisphere. But as no mean errors 

 are computed, it is difficult to say whether this difference is merely accidental. 



In the discussion of the position of the rotation-axis in connection with the 

 latitude-motions of the spots, we recur to the writings of Dyson and Maunder. 



The Distribution of the Sun-spots. Concerning the distribution of the 

 sun-spots on the sun's surface, the investigations have up till now almost exclusively 

 dealt with the distribution in latitude. Even Scheinee had observed that there 

 never occurred any spots in the neighbourhood of the poles of the sun, but only 

 in two zones on both sides of the equator. This point was not perfectly clear 

 until the nineteenth century, when the extensive material of observation rendered it 

 possible to examine the distribution completely. Then it became evident that sun- 

 spots at higher latitudes than 'åb^ were only sporadic phenomena. Very seldom 

 does any spot occur at higher latitudes than 40". Within the sun-spot belt, 80** 

 wide, the spots occur mainly in two zones in either hemisphere, between tlie lati- 

 tudes 5° and 20^ 



As Sporer ^, from his observations between 1854 — 1880 has shown, the 

 mean heliographie latitude of the sun-spots is subject to regular variations. The 

 first sun-spots of every new period appear on higher latitudes, and as the period 

 advances, the mean latitude of the spots is diminished in both hemispheres. This 

 peculiarity, known as »fhe hiw of Sporer» has since been further confirmed by 

 Maunder^. The researches by Maunder embrace the time from 1874 — 1902, and 

 are founded on the photographs of the sun taken at Greenwich and other English 

 observatories. In table IV, I have placed those observations together, on which the 

 present paper is based. Yvom this table the law of Sporer appears with all desi- 

 rable clearness. 



On the distribution of the sun-spots in heliographie longitude no researches 

 have been made hitherto, as far as I know. Several times, however, it has been 

 observed that an intense spot-activity takes place on opposite sides of the sun at 

 the same time. A research into the distribution of the spots in longitude is made 

 more difficult as the sun rotates with different angular velocity at different lati- 

 tudes. This circumstance makes it inconvenient to extend the research for any 

 long period. 



A comparison between the number of spots on the left and on the right halves 

 of the sun gives the unexpected result that there are more spots observed on the 

 left half than on the right. It is evident that from this fact we must not draw the 

 conclusion that there actually are more spots on the left side of the central meridian 

 than on the right, provided that the earth has not considerable influence on the spot- 



' G. Spokek: Beobachtung der Sonnenflecken etc. Astronomische Nachrichten 96. 1880. 

 - E. W. Maunder : Note on the Distribution of Sun-Spots in Heliographie Latitude. Monthly 

 Notices LXIV, 1904. 



