DR. miller’s EXETER LECTURE. 
347 
May 1866 a star suddenly burst forth in the constellation of 
the northern crown. On examining its spectrum, a wonderful 
condition of things was rendered visible, which will be made 
intelligible by examining a representation of the spectrum of 
this star — T coronse, as it is called — Plate L., fig. 8. This star 
exhibits three different spectra ; two of them resemble the 
spectra of the stars in general, consisting, that is, of the con- 
tinuous spectrum of the nucleus, crossed by the spectrum of 
dark lines produced by the gaseous bodies contained in its outer 
atmosphere. But in addition to these is another spectrum, 
composed of four or, perhaps, five bright lines. This is the 
spectrum of a gaseous body in a state of intense incandescence, or 
glowing heat ; and the position at c and f of the principal bright 
lines shows that one of the luminous gases is hydrogen. The 
great brightness of these lines shows, too, that the gas is hotter 
than the body of the star itself. These facts, taken in con- 
nection with the suddenness of the outburst of light, and its 
very rapid decline in brightness (from the second magnitude to 
the eighth magnitude in twelve days), that is to say, from a 
bright star to one invisible without the aid of the telescope, 
suggests the startling probability that the star had become sud- 
denly enwrapt in the flame of hydrogen which was burning 
around the star and combining with some other element. As 
the hydrogen gradually became exhausted, the flames dimi- 
nished in intensity, and the brightness of the star declined in a 
corresponding proportion. 
I must yet mention one more of the class of objects which 
occur in the heavens, still more enigmatical than any which I 
have at present described, and upon the nature of which spec- 
trum observations have thrown an unexpected amount of 
information ; I mean the nebulce. When the eye is aided by a 
telescope of moderate power, a large number of faintly luminous 
patches and spots are distinguished in the sky, which differ 
entirely in appearance from the defined brilliant points of light 
formed by the stars. Many of these singular objects, when 
viewed by the most powerful telescopes, still resemble mere 
shining clouds. These objects have been a standing puzzle to 
astronomers, and the interest connected with their nature has 
been increased by the suggestion of Sir W. Herschel, that they 
were possibly portions of the original material out of w^hicli 
existing suns and stars have been formed, and that probably in 
these nebulae we may actually watch some of the stages through 
which suns and planets pass before they take their final shape. 
Spectrum analysis, if it could be applied to these excessively 
faint objects, would immediately show wdiether they had a con- 
stitution like that of ordinary stars or not. Certain of these 
bodies when thus examined give no continuous spectrum, but 
