300 Professor Piazzi Smyth on a Centauri, 
ness of so large a proportion of the stars is then naturally accounted 
for by their greater proximity to us; and this fact was actually 
proved by my predecessor, who found from his own observations of 
a Centauri, an annual parallax of the large amount of 1”, i. e., that 
at the distance of this star, the radius of the earth’s orbit, or 95 
million of miles, subtended an angle of 1”; the greatest quantity 
previously found for any star in the Northern hemisphere being only 
0-23”. 
Professor Henderson’s results were fully confirmed by a very 
much longer series of observations subsequently made at the Cape 
Observatory by different observers, and with different instruments, 
and he then computed his old observations of the other principal 
stars in that region, and finding a considerable number* which 
shewed also indications of a sensible parallax, he immediately sent 
out a notice of the results to the present energetic Director of the 
Cape Observatory, for the purpose of procuring from him a greater 
number of observations of those suspicious stars. Such a series was 
accordingly commenced, and is still going on, and we may expect be- 
fore long to hear of trustworthy results having been obtained, and 
there is little doubt that these labours will still more strongly tend to 
establish the proximity of that part of the sky. 
On the application of the telescope to @ Centauri, it proves to be 
composed of two stars, one very much brighter than the other, but 
still both may be placed in the list of first magnitude, the smaller 
occupying the lowest possible step in that grade. Early observers 
have indeed assigned it a much smaller rank, and in the British 
Association Catalogue published only two years ago, and intending 
to apply to the year 1850, it is actually made as low as the fourth 
magnitude ; this, however, is manifestly an error, for the present 
epoch, as I can state from the experience derived from making the 
observations which served to confirm Professor Henderson's parallax ; 
for, during the whole year, there was not a single day when, if the 
larger star was seen at all, the smaller one was not abundantly visi- 
ble also; and during that part of the year when they transited the 
meridian by daylight, they were even then invariably seen with the 
mural circle telescope, whatever the state of the atmosphere, unless 
actual clouds intervened. But that the smaller star was never in 
ages past as low as the fourth magnitude, the marvellous change which 
has occurred in the case of » Argus in our own times, would render 
a most hazardous assertion. 
nS 
r - 
XRT 
* p Hydri. » Argus. + Centauri. me 
« Phenicis. « Crucis. « Trianguli Austr, = 
a Bridani. y Crucis. 8 Trianguli Austr, 1) 
a Columbe. 6 Crucis. « Payonis. oe 
s Argus. 6 Centauri. « Gruis. . Sita 
VitSIo 
if 
s a 
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