172 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1923 



Thus it is evident that the disturbed state of the sun's surface 

 affects the earth. But there is also some evidence that the earth ap- 

 pears to affect the sun's surface. This appears in a slight, but dis- 

 tinct, dissymmetry between the eastern and western halves of the 

 apparent disk of the sun, with respect to three orders of solar phe- 

 nomena: the numbers of prominences; the areas of faculse; and the 

 numbers and areas of spot groups. There is some evidence that the 

 amount and the sign of this dissymmetry vary in the course of the 

 solar cycle. A complete explanation is still to seek. 6 



These conclusions and suggestions have been derived, during the 

 century of the history of this Society, from observations of the 

 changes, real and apparent, of the areas of sunspots and of their 

 distributions in longitude and latitude. 



APPENDIX * 



In the two years since the writing of the original paper, several 

 expressions for the rotation period of the sun, "varying with the 

 latitude, have been found for faculse and flocculi, phenomena which 

 differ in character from sunspots and from each other. Comparing 

 the zones, 5° in breadth, of greatest activity (those with their cen- 

 ters at 12y 2 ° on either side of the Equator) for five of these investi- 

 gations, we have the following result : 



Table I 



Spots observed from 6 to 14 days 



Facute 



Flocculi 



Recurrent spots 



Faculas 



Authority 



Maunder. 

 Newton.. 

 Fox 



Maunder. 

 Chevalier 



Daily 

 sidereal 



motion 



14?45 

 14.42 

 14.38 

 14.34 

 14.33 



Mean 

 synodic 

 rotation 



period 



26?74 

 26.79 

 26.89 

 26.95 

 26.98 



It will be seen that the extreme difference from the mean is only 

 0.12 of a day. 



But these are all mean values for the zone ; the scattering shown by 

 the individual objects in any zone is as marked and significant as 

 is the crowding round the mean rotation period in that zone. For 

 example, for spots observed from 6 to 14 days the most active zones 

 have synodic periods ranging from 23-4 to 30^0 and f aculse and floc- 

 culi both show a scattering of about the same order. 



B Monthly Notices, 47, 451 : "An apparent influence of the earth on the numbers and 

 areas of sunspots In the cycle 1889-1901 " ; and Memoirs of the British Astronomical 

 Association, 23, Part II, " Report of the section for tne observation of the sun, 

 1910-1919 " ; " The distribution of facula? between the four quadrants of the sun's appar- 

 ent disk," p. 46. 



• Added June 17, 1924. 



