THE' SUN AND SUNSPOTS MAUNDER 



169 



The different rotation periods given by long-lived spot groups dur- 

 ing their successive^apparitions are illustrated in figure 6, which 

 exhibits the distribution in longitude of all groups lasting through 

 three or more successive rotations during the years 1891-1894. The 

 recurrent groups north of the Equator are marked N, those south of 

 it S. It may be assumed that the greater the depth below the surface 

 of the place of origin of a given spot group, the greater will be the 



Distribution of Spot- Groups of Lo-nq duration in tht Years /8<JI tc I8<jif. 

 in Hclio jrapTito Longitude. 



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3S0 30C 



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270 



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Tk* Jots i^iicati. rite HiliojraTiJuc Lonjitude o^ each Group ©^ Spot) wTicn on thi Central 

 Meridian of the Suit's Disc. 



W5 



Fig. 6 



difference of its observed rate of motion from the general surface 

 drift. 



The seventh diagram is drawn upon precisely the same scale as 

 figure 6, and shows the distribution of certain solar longitudes. But 

 these are not longitudes of spots on the sun, but of the center of the 

 sun's disk at the moment when a magnetic storm began to be felt upon 

 the earth. In this case every magnetic storm is recorded. It will be 

 seen how similar is the character of the associated dots in the two 

 figures; even though no spots are given in figure 6 that made only 



