SPECTRUM ANALYSIS OF THE HEAVENLY BODIES. 147 
principal of the bright lines of this spectrum inform us, by their position, 
that one of the luminous gases is hydrogen. The great brightness of 
these lines shows that the luminous gas is hotter than the photosphere. 
These facts, taken in connexion with the suddenness of the outburst of 
light in the star and its immediate very rapid decline in brightness, from 
the 2nd magnitude down to the 8th magnitude in twelve days, suggested the 
startling speculation that the star had become suddenly enrapt in the flames of 
luminous or burning hydrogen. In consequence, it may be, of some great 
convulsion enormous quantities of gas were set free. A large part of this gas 
consisted of hydrogen, which was either intensely glowing, or burning about 
the star in combination with some other element. This flaming gas emitted 
the light represented by the spectrum of bright lines. The spectrum of the 
other part of the star’s light may show that this fierce gaseous conflagration 
had heated to a more vivid incandescence the solid matter of the photosphere. 
As the free hydrogen became exhausted the flames gradually abated, the 
photosphere became less vivid, and the star waned down to its former 
brightness. 
We must not forget that light, though a swift messenger, requires time to 
pass from the star tous. The great physical convulsion, which is new to us, 
is already an event of the past with respect to the star itself. or years 
the star has existed under the new conditions which followed this fiery 
catastrophe. 
Nrsu.z, 
When the eye is aided by a telescope of even moderate power, a large 
number of faintly luminous patches and spots come forth from the darkness 
of the sky, which are in strong contrast with the brilliant but point-like 
images of the stars. A few of these objects may be easily discerned to con- 
sist of very faint stars closely aggregated together. Many of these strange 
objects remain, eyen in the largest telescopes, unresolved into stars, and 
resemble feebly shining clouds or masses of phosphorescent haze. During 
the last 150 years the intensely important question has been continually 
before the mind of astronomers, ‘“‘ What is the true nature of these faint, 
comet-like masses ? ” 
The interest connected with an answer to this question has much increased 
since Sir Wm. Herschel suggested that these objects are portions of the pri- 
mordial material out of which the existing stars have been fashioned; and 
further, that in these objects we may study some of the stages through 
which the suns and planets pass in their development from luminous cloud. 
The telescope has failed to give any certain information of the nature of 
the nebule. It is true that each successive increase of aperture has resolved 
more of these objects into bright points, but at the same time other fainter 
nebulz have been brought into view, and fantastic wisps and diffused 
patches of light have been seen, which the mind almost refuses to believe 
can be due to the united glare of innumerable suns still more remote. 
Spectrum analysis, if it could be successfully applied to objects so exces- 
sively faint, was obviously a method of investigation specially suitable for 
determining whether any essential physical distinction separates the nebulz 
from the stars. 
The speaker selected for the first attempt, in August 1864, one of the 
class of small, but comparatively bright nebule. 
His surprise was very great, on locking into the small telescope of the 
spectrum apparatus, to perceive that there was no appearance of a band of 
coloured light, such as a star would give; but in place of this, there were 
M2 
