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INFLUENCE OF PLANETARY CONFIGURATIONS UPON 

 THE FREQUENCY OF VISIBLE SUN SPOTS 



By FERNANDO SANFORD 

 Palo Alto, California 



In any discussion of sun-spot frequency it should be borne in mind 

 that only one-half of the Sun is visible to us at one time, and that 

 all sun-spot data refer only to spots on the terrestrial side of the 

 Sun. 



In 1907 A. S. D. Maunder published a paper entitled "An xA.pparent 

 Influence of the Earth on the Numbers and Areas of Sun-spots in 

 the Cycle 1889-1901." ^ Mrs. Maunder found that for the years under 

 consideration more spots came into view around the east limb of the 

 Sun than passed out of view around the west limb ; that is, that more 

 spots died out on the visible side of the Sun than were formed on it. 

 As a summary of Mrs. Maunder's observations we have the follow- 

 ing tal)le : 



Spots born on visible hemisphere 384 



Spots born on invisible hemisphere 5/2 



Spots died on visible hemisphere 564 



Spots died on invisible hemisphere 402 



All told, 947 groups came into view around the east limb or formed 

 close to it, and only /"/y groups passed around the west limb or dis- 

 solved close to it. This leaves a difference of 170 groups, or 22 per- 

 cent of the disappearances, which seem to be due to some influence 

 exerted by the Earth. Apparently, the Earth exerts an inhibitive 

 influence upon the formation of sun spots upon its own side of the 

 Sun or aids their formation upon the opposite side, or, perhaps, both. 

 This plain inference seems not to have been tested in the case of 

 other planets. 



It is reasonable to infer that whatever influence the Earth may have 

 on sun spots, a similar influence may be exerted by the planet Venus, 

 which is comparable in size and mass to the Earth and is less than 



' Monthly Not. Roy. Astronom. Soc, May 1907. 



Smithsonian Miscellaneous Collections, Vol. 95, No. 11 



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