2JO 
PRELIMINARY GENERAL CATALOGUE OF STARS FOR 1900 
and similarly for declination. The unit of r is one century. We take as centennial /iq, 703"5; 
for fi, + 3990 ; and for //, — 579'.'o, these being the instantaneous values assumed for 1875. Then 
the solution of the conditional equations gives: 
From R.A., \ — (centennial) = —"0084; = — ''0296 ± ('0380 
dt 
dt 
From deck, ^ ^-(centennial) = —'.'0173; = + ''0420 ± ''0214 
dt dt 
Assigning to these two results weights, one for R.A. and 3 for deck, in close accordance with their 
respective probable errors, we have as the value of determined from the meridian-observa¬ 
tions: 
dt 
— +''0241 ±'.'0190 
dt 
In the case of Groomb 1830, —— may be found in another way. Let n be the annual parallax 
dt 
of a star, its centennial proper-motion in arc, and l its radial motion in kilometers per second, 
then, after Seeliger (Ast. Nach., Bd., 154, s. 67): 
A/aq _ 
dt 
.00000205 l/M) TT 
If, now, for Groomb 1830 we put l = — 96 km. from the result obtained at the Lick Observatory; 
fi' = 703''5; and 7r = V'i2, we have, 
fVo 
dt 
+ '/oi66 
in good agreement with the value of the same quantity derived from meridian-observations. As 
there is some uncertainty in the determination of motion in the line of sight for so faint a star, and 
proportionately still greater uncertainty in a parallax so small, it may be assumed that a more 
probable result would be reached by adopting the mean of the values derived from the two dif¬ 
ferent sources or: 
Adopted = + "0204 
dt 
The resulting corrections to the secular variations computed in the ordinary way, as for other stars 
in the Catalogue, are: 
--- = -H00098 ~~ = — "0168 
dt dt 
which have been adopted. It is probable that the adoption of these quantities may result in a 
smaller error of prediction than would have resulted from their rejection. 
No. 3307. y Virginis. 2 1670. 3 M 6-3 M 6. 
This is a celebrated binary system having a period of about 194 years according to See (Stellar 
Systems). See’s orbit is here adopted in computing the relation of the separate stars to the center 
of gravity. Since the effective meridian-observations cover only about one-half of the orbital 
period, there is serious indetermination between the orbital and proper-motion. However, both of 
the stars have been well observed; and the comparatively equal brightness of components is prob¬ 
ably favorable to relatively small systematic errors of observation wherever the mean has been 
observed. Assuming the star which is now south-following to be the principal star, the distance 
of the center of gravity from it in terms of the distance, p, between the two components is found to 
be as follows: 
From observations of y 1 , R. A., 
0.30 
wt. 1 
Deck, 
0.56 
wt. 2 
From observations of y 2 R. A., 
0.49 
Wt. I 
Deck, 
0.65 
Wt. 2 
Mean by weights 
0-54 
