NO. II FREQUENCY OF VISIBLE SUN SPOTS SANFORD 3 



at an angular distance of 90 degrees — and the sun-spot numbers for 

 each of these 100 days are given in table 2. 



Table 2. — The Earth and Venus at an angular separation of ninety degrees 



Sept. 18, 

 July 3, 

 Apr. 2, 

 Feb. 6, 

 Nov. 26, 

 Sept. 15, 

 July 2, 

 Apr. 17, 

 Feb. 3, 

 Nov. 26, 



1917 

 1918 

 1919 

 1920 

 1920 

 1921 

 1922 

 1923 

 1924 

 1924 



38 



79 

 120 



34 

 29 

 32 



370 



Sum . 



The mean sun-spot number for the 100 days of the above table is 

 43.29, whereas for the 50 days near superior conjunction it was 68.1 

 and for the 50 days near inferior conjunction it was 38.5. 



It would appear from these results that the influence of Venus on 

 visible sun-spottedness is much greater when the planet is on the oppo- 

 site side of the Sun from the Earth than when it is on the same side 

 as the Earth. That is, the apparent effect of Venus upon sun spots is 

 to repel them to the farther side of the Sun. The phenomena ob- 

 served by Airs. Maunder indicate that the Earth also apparently repels 

 sun spots to the farther side of the Sun. 



In the case of Mercury and the Earth, the eccentricity of the ellip- 

 tical orbit of Mercury is so great that the distance of the planet from 

 the Sun is more than 1.5 times as great at aphelion as at perihelion. 

 It seems probable that the distance of Mercury from the Sun must 

 influence whatever effect it may have on total sun-spottedness, and its 

 position relative to the Earth must influence the visibility of these 

 spots. 



The period of siderial revolution of Mercury is 88 days. Its synodi- 

 cal period is 116 days. Accordingly, superior conjunction with the 

 Sun will occur every 116 days, and perihelions will be 88 days apart. 

 If we assume that both of these positions are favorable to the produc- 

 tion of visible sun spots, their resultant influence is very hard to deter- 

 mine. Also, Mercury moves in its orbit 2.3 times as fast at perihelion 

 as at aphelion, and is 33 days on the perihelion side of the Sun and 55 

 days on the aphelion side. 



