30 THE ROYAL SOCIETY OF CANADA 
Synodie radial Compt. at limb — v. 

Fr . 
: R 
Sidereal “ 7 OUEST: a +s 
: : 3 R 
Sidereal velocity of rotation V = > (° ets ‘) sec 7 
¢/— 18 
Where £ and £/— are the angular velocities at the limb and at the 
mean latitude ¢ of the observed points @, and g, obtained from the 
second method 
Ë (Adams) = 11°.04 + 8°.5 cos? ©. 
12. Second Method—Corrections at observed points. 
(a) Determine the heliographic latitudes @, and ©, of the observed 
points by the Greenwich method 
sin g — cos p sin D + sin pcos D cos ¥ 
(sin pand cos p obtained from De LaRue’s tables argument = 
: 
also the differences of longitude À, and À, 
sin A — sin ¥ sin p sec ¢. 
(b) Determine the angles 7,, 7, at the two observed points 

7 - 
Gos 7 COS D cos ( aa 1) 
a 
(c) Divide the total sidereal radial velocity into the two following 
parts proportional to the angular velocities at the latitudes g,, g, (ob- 
tained closely enough from Adams’ formula § = 11°.04 + 3°.5 cos? g) 
( Y =, ; or 
SAT : Ss = = > 2(» +> — S tn 
R te Ay ER 
(d) Sidereal Velocities of Rotation :— 


For c and d may preferably be substituted the following practically 
identical but simpler method. 

+ Instead of taking the mean latitude "1 + 2 it is more correct to take the 
2 
angle ¢! such that 11°.04 + 3.5 cos? g!= 4} (119.04 + 3.5cos?¢, + 11°.04 + 3.5 
cos?¢,). This was not necessary in Series I and III but in Series II this differ- 
ence in one case reaches 23’ which changes the correction slightly. 
