302 Professor Piazzi Smyth on a Centauri, 
when at the Cape, and had far superior instruments for such a pur- 
pose to any of his predecessors; he thus describes and sums up all 
that was known to him of this star, in his recently-published work. 
** This superb double star, beyond all comparison the most. strik- 
ing object of the kind in the heavens, and to which the discovery of 
its parallax by the Jate Professor Henderson has given a degree of 
astronomical importance no less conspicuous,—consists of two indi- 
viduals, both of a high ruddy or orange colour, though that of the 
smaller is of a somewhat more sombre and brownish cast. They 
constitute together a star which to the naked eye is equal or some- 
what superior to Arcturus in lustre.’ After describing the mag- 
nitude which he considered should be assigned to each, and which 
agrees more nearly with what I have already stated as being my own 
opinion, and after giving some optical and physiological reasons which 
may tend to explain the under-estimation of former observers,—Sir 
John then cites the fact of the remarkable amount of proper motion 
of the stars, and says, ‘‘ This consideration alone suffices to decide 
us in admitting a binary connection between them, and it will there- 
fore be interesting to see what evidence observation furnishes of or- 
bitual motion round their centre of gravity. For this, however, the 
data are somewhat precarious, as we have, until recently, only cata- 
logued differences of A.R. and Polar distances, from which to caleu- 
late the angle of position and distance at the epochs of observation. 
This done, and the results tabulated, together with my own positions 
and distances, obtained by direct measurement with the equatorial, 
we have as follows :’’— 
Authority. Oe eas Position. Distance. 
° / 
Lacaille, 1750 218 44 20°51 
(Maskelyne, 1761 15°5) 
Fallowes, 1822 209 36 28°75 
Brisbane, 1824 215 25 22°45 
Dunlop, 1825 213 11 22°45 
Johnson, 1830 215 2 19°95 
Taylor, 1831 215 58 22°56 
Herschel, 1834-68 17°43 
1834-79 218 30 
1835-86 219 30 
1837-34 220 42 
1837-44 16:12 
I have inserted here the observation of Maskelyne in 1761, with 
which, probably, Sir J. Herschel was unacquainted ; it makes an ap- 
