1921 .] 
Astronomical Notes. 
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193 
The heliocentric equatorial co-ordinates of the comet are 
— r sin a sin (A + w -f- w) = r X 0*94749 X sin (358° 51' 17" + w), 
y^~r sin b sin (B -j- a> -f- w) = r X 0-94179 X sin (275° 46' 29" 4- w), 
z 4 — r sin c sin (C + o> + w ) — r X 0-46400 X sin (228° 44' 12" -j- iv). 
For E = + 5°, r = 1-04833, and w = -j- 11° 22' 54" ; 
hence z 4 = + 0-17652, = — 0-94337, z 4 = — 0-42176. 
A check is obtained from the equation a? 4 2 -f- y^ 2 + z 4 . 2 = r 2 - 
In this case cc 4 2 + y± 2 + z 4 2 = 1*09898) 
and r 2 = 1-09899 i 
The next step is to obtain the Sun’s equatorial co-ordinates for the 
date corresponding to E — -j- 5°. The date is 1921 June 22-455 G.M.T., 
and for this date the co-ordinates are interpolated from the British 
Admiralty Nautical Almanac , and are 
X = — 0-01806, Y = + 0-93237, Z = + 0-40438. 
The geocentric distance A, the right ascension a, and the declination 8 
of the comet are obtained from 
A cos a cos 8 = X + £C 4 , 
A sin a cos 8 = Y + y±, 
A sin 8 = Z + 2 4 ; 
and are = 0-15978 astronomical units = 14-8 million miles, 
a — 23h. 44m. 3s. 
8 = 6° 14' 28" S. 
13—Science. 
