SPECTRA OF SOME OP THE BRIGHTER STARS. 
711 
The Passage to Bright-line Stars. 
On the hypothesis, the lines seen in the spectra of bright-line stars should, in the 
main, resemble those which appear in nebulae. They will differ, however, for two 
reasons :— 
(1.) Owing to partial condensation of the swarm the hydrogen area will be 
restricted, and the bright lines of hydrogen will lose their prominence ; 
the volume occupied by the carbon compounds will be relatively increased, 
and the brightness of the carbon bands will be enhanced. 
(2.) On account of the increased number of collisions, more meteorites will be 
rendered incandescent, and the continuous spectrum will be brighter than 
in nebulae. 
Stars of Increasing T'empera t ure. 
Initially, each pair of meteorites in collision may be regarded as a condensation. 
Ultimately, when all the meteorites are volatilized, there will only be one conden¬ 
sation, in the shape of a spherical mass of vapour. Between these points there must 
be other conditions. 
(Stage 1.)—At the stage of condensation immediately following that of the 
bright-line stars, the bright lines from the interspaces will be masked by 
corresponding dark ones produced by the absorption of the same vapours 
surrounding the incandescent meteorites. One part of the swarm will give 
bright lines, another dark lines at the same wave-lengths, and these lines 
will therefore vanish from the spectrum. The interspaces will be restricted 
so that absorption phenomena will be in excess, and the first absorption 
will be that due to low-temperature vapours, that is, fluting absorptions of 
various metals. The radiation spectrum of the interspace will now be 
chiefly that of the compounds of carbon. Under these conditions we know 
from laboratory experiments* that the amount of continuous absorption at 
the blue end will be at a maximum, 
(Stage 2.')—With further condensation the radiation spectrum of the interspaces 
will gradually disappear, and the fluting absoi’ptions will be replaced by 
dark lines, for the reason that the incandescent meteorites will be surrounded 
by vapours produced at a higher temperature, the number of violent colli¬ 
sions per unit time and volume being now greatly increased. This dark line 
spectrum need not necessarily resemble that of the Sun. 
(Stage 3.)—The line absorption and the continuous absorption at the blue end of 
the spectrum will diminish as the condensations are reduced in number, for 
the reason that only those vapours high up in the atmospheres surrounding 
* Lockyer and Roberts-Austen, ‘Roj. Soc. Proc.,’ 1875, p. 344. 
