146 
Transactions of the Boyal Society of South Africa. 
spectrum, class A2 ; the combined magnitude of the double-star 2 1757 
is 7-36. The galactic co-ordinates of ^ Virgo are: — 
\ = 270°19' /3=+61°0' ^ = 21° 9' 
and 
-0"-526 ^^=+0"-135 
with 
^/, = 0"-288 towards 297°-9. 
Its distance cl from the solar apex is 70° 44', and ^ the position angle of 
the great circle drawn through the star to the solar apex is 58° 2' ; from 
these we find r the component of proper motion perpendicular to the 
plane through the sun, star, and apex, and therefore independent of 
the solar motion to be equal to +0"*181 and —v the motion in the plane, 
and increasing the angular distance from the solar apex to be + 0"-225. 
Adopting as applicable to this system Dr. Campbell's average parallax 
for stars of class A2, viz., 0"-01, the present angular distance projected on 
to the tangent or visual plane corresponds to a distance of about 100,000 
units," which is probably too great. It will be remembered that a Cen- 
taurus is about 270,000 units distance from the solar system. No deter- 
mination of the radial velocity of ^ Virgo has been found. 
Although it is now well known that stars in all parts of the heavens are 
travelling in several streams, or, in other words, that widely scattered 
stars can be grouped in communities of similarly directed motion, cases of 
stars close together in the sky but too widely apart to be classed as 
double -stars, that is, with distances exceeding 2' but within a degree or 
so, and travelling together with a large proper motion — and any proper 
motion over 15" in a century must be considered large — are sufficiently 
rare. Other cases are the two double-stars k- Toucan and Lacaille 353, 
which are 320' apart, and have a common proper motion of 0"'407 
towards 86°'2 ; and A Ophiuchus (a double-star) and Bradley 2179, which 
are about 800" apart and have a common proper motion of l"-250 towards 
204°-5. A good example of stars widely separated, but with a proper 
motion so large and unusual that they can at once be picked out, is 
furnished in the case of ^Eeticulum (a wide double-star) and 
e Eridanus, viz. : — 
Har.mag. 
Har 
Spect. 
E.A. 1900. 
Dec. 
Proper Motion. 
Keticulum 
5-48 
G 
3'^ 15"' -6 
- 62° 57' 
-f 0s'195 +0"-68 
4-30 
G5 
3 15 -9 
- 43 27 
+ 0 -282 -f 0 -75 
5 -16 
F8 
3 16 -0 
- 62 53 
+ 0 -192 + 0 -69 
* The unit is equal to the mean distance of the earth from the sun. 
Johannesburg, Oct. 30, 1913, 
