APPLIED TO THE HEAVENLY BODIES. 203 



On tlie 12th of May last a star of the second magnitude suddenly burst fortli 

 in the constellation of the Northern Crown. Thanks to the kindness of the 

 discoverer of this phenomenon, Mr. Birmingham, of Tuam, I was enabled, con- 

 jbinlly with Dr. Miller, to examine the spectrum of this star on the l(jth May, 

 Avhen it had not fallen much below the third magnitude. 



I ought to state that Mr. Barker, of London, Canada West, who announced 

 an observation of this star on 14th May in tlie Canadian Free Press, now claims 

 to have seen the star on May 4th, and states that it increased in brilliancy up to 

 May lOtli, when it was at its maximum. 



The spectrum of this star consists of two distinct spectra. One of those is 

 formed by these four bright lines. The other spectrum is analogous to the spectra 

 of the sun and stars. 



These two spectra represent two distinct sources of light. Each spectrum is 

 formed by the decomposition of light which is independent of the light which 

 gives birth to the other spectrum. 



The continuous spectrum, crowded with groups of dark lines, shows that there 

 exists a photosphere of incandescent solid or liquid matter. Further, that there 

 is an atmosphere of cooler vapors, which give rise by absorption to the groups 

 of dark lines. 



So far the constitution of this object is analogous to that of the sun and stars ; 

 but in addition there is the second spectrum, which consists of bright lines. 

 There is, therefore, a second and distinct source of light, and this must be, as 

 the character of the spectrum shows, lummous gas. Now the position of the 

 two principal of the bright lines of this spectrum informs us 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 fticts, taken in connection 

 with the suddenness of the outburst of light in the star, and its immediate very 

 rapid decWne in brightness from the second magnitude down to the eighth mag- 

 nitude in twelre days, suggested to us the startling speculation that the star had 

 become suddenly enrapt in the flames of burning hydrogen. In consequence, it 

 may be, of some great convulsion, enormous qimntities of gas were set free. A 

 large part of this gas consisted of hydrogen, which was burning about the star 

 in combination with some other element. Tliis flaming gas emitted the light 

 represented by the spectrum of bright lines. The increased brightness of the 

 spectrum of the other part of the star's light may show that this tierce 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 to us. The great physical convulsion which is new to us is already 

 an event of the past with respect to the star itself. For years the star has ex- 

 isted under the new conditions which followed this fiery catastrophe. 



NEBUL.E. 



I pass now to objects of another order. 



When the eye is aided by a telescope of even moderate power, a large num- 

 ber of faintly luminous patches and spots come forth from the darkness of the 

 sky, Avhich are in strong contrast with the brilliant but point-like images of the 

 stars. A few of these objects may be easily discerned to consist of very faint 

 stars closely aggregated together. Many of these strange objects remain, even 

 in the largest telescopes, unresolved into stars, and resemble feebly shining clouds, 

 or masses of phosphorescent haze. During the last loO years, the intensely im- 

 portant question has been continually before the mind of astronomers, " What is 

 the true nature of these faint, comet-like masses V 



