174 Transactions.— Miscellaneous. 
same as the solar lines. Such a result would surprise me much. The D. 
sodium line, the E. iron line, the b magnesium line, and the F. hydrogen line 
of the Sun have, almost certainly, their counterparts in the spectrum of a 
Centauri. "There can be little doubt that the physieal constitution of this 
great star is, in most respects, the same as that of the Sun. It is probable, 
however, that a Centauri is less developed than the Sun ; for, as Mr. Proctor 
has pointed out, its light is brighter than its mass would lead us to expect 
itto be, judging from the light of our Sun, as compared with his mass. 
While the mass of the star is to the mass of the Sun as 2: 1, the light of 
the star is to the light of the Sun as 8:1. Now, if it is true, as physicists 
have good grounds for believing, that the Sun is, and has been, very slowly 
but surely losing his heat, just as our earth has most certainly lost an 
enormous amount of hers, there must have been a time when the Sun and 
his system were less developed, but far hotter and brighter than they are 
now—when they formed, probably, as I said when speaking of y Crucis, & 
white star—that is to say, there was, quite possibly, a time when the light 
from our Sun bore the same relation to his mass as the light from a Centauri 
bears to its mass. We may also believe that matters are less advanced in 
the planets (if there are any) of this neighbouring system than they are 
with us. 
a Trianguli.—The spectrum of this star is not very striking, but it is 
rather curious, as showing, apparently, that the star is in a condition inter- 
mediate between that of a Centauri and that of y Crucis. The lines of the 
second class, and also the groups, are very faint, but they arethere. Tt will 
be seen that this fact has some bearing on the suggestion I made respecting 
the gradual development of stars while speaking of y Crucis. Here it looks 
asif we had, so to speak, caught a star in the act of changing from the 
second to the third class. What I have seen of the spectra of the stars, so 
far, leads me to think it probable that if every star, down to the sixth mag- 
nitude, could be examined even with my instrument, and mapped roughly, 
i& would be found that the spectra obtained could be so classified that a 
series might be made, each member of which would differ from the next 
almost insensibly. This, of course, would take a long time to do, as small 
stars can be examined only in very fine weather. When it was done, how- 
ever, the results would be very valuable and interesting. 
a Gruis.—This is a second-magnitude white star, with the usual spec- 
trum crossed by distinct hydrogen lines. 
B Gruis is a second-magnitude star, and nearly as bright as the lucida 
of this constellation. Its colour is reddish-orange, and its spectrum is 
much like that of y Crucis, but the groups of lines are not so distinct, 
and, generally, there is a sort of approach to the appearance presented by 
