and the Absolute Size of the Fixed Stars. 299 
now, as the perihelion passage of the small star is close at 
hand ; and, on the correct observation of the phenomenon at 
that particular epoch, all exact determination of the great de- 
siderata previously mentioned, will depend. 
As, however, another opinion has been published, with re- 
gard to the nature of the orbit of a! and a? Centauri; and, if 
observers are guided by that, and it should not prove to be 
correct, all this important part of the orbit which seems to 
be impending, may be lost to us ; and near a hundred years 
must elapse before another equally favourable opportunity 
occurs, it becomes of importance to examine into the exact 
particulars, and see what degree of probability is to be at- 
tached to either hypothesis. 
For the first part of the question, I may refer to a notice 
which I had the honour of reading before the Royal Society 
of Edinburgh, on April 5, 1848. 
The star @ Centauri, situated in 14" 29m A.R., and 150° 12’ 
N.P.D., is in many respects a notable object, and though its great- 
est claims to attention have all arisen within the last few years, 
under the applications of the advanced astronomy of the present 
day, yet even to the naked eye it has much to raise it above the 
general crowd. It is a star of the first magnitude, and one of the 
brightest indeed of that class, and is situated in a peculiarly splen- 
did region of the sky, the same as that occupied by the Southern 
Cross; a constellation, by the way, which, on account of its small 
dimensions, and the few stars it contains visible to the naked eye, 
is by no means entitled to the too warm encomiums so lavishly be- 
stowed upon it by the early Southern navigators and travellers. The 
region of the Cross, however, abundantly compensates for the poverty 
of the constellation itself; for such is the general blaze of star-light 
from that part of the sky, that a person is immediately made aware 
of its having risen above the horizon, though he should not be at the 
time looking at the heavens, by the increase of general illumination 
of the atmosphere, resembling the effect of the young moon. 
This excessive splendour is caused not only by the profusion of 
first, second, and third magnitude stars in the neighbourhood, but 
by the extraordinary general breadth and brightness of the Milky 
Way thereabouts; for, separating into so many distinct luminous 
clouds, as it were, and exhibiting between them void black spaces 
unchequered by a single luminous object of any kind whatever, it 
forcibly impresses the idea of our being situated there near the confines 
of the sidereal system, or in the southern side of the vast ring in 
which the generality of the stars are arranged. The superior bright- 
