482 Mr. W. Huggins on the Spectrum of Comet 11,, 1868. [June 18, 



numerous fine lines, which accompanies the Hnes appears as an unresolved 

 nebulous light. 



On June 23 the spectrum of the comet was compared directly in the 

 spectroscope with the spectrum of the induction spark taken in a current 

 of olefiant gas. 



The three bands of the comet appeared to coincide with the correspond- 

 ing bands of the spectrum of carbon. In addition to an apparent identity 

 of position, the bands in the two spectra were very similar in their general 

 characters and in their relative brightness. 



These observations were confirmed on June 25. 



The remarkably close resemblance of the spectrum of the comet with 

 that of the spectrum of carbon, necessarily suggests the identity of the sub- 

 stances by which in both cases the light was emitted. 



The great fixity of carbon seems, indeed, to raise some difficulty in the 

 way of accepting the apparently obvious inference from these prismatic 

 observations. Some comets have approached sufficiently near the sun to 

 acquire a temperature high enough to convert even carbon into vapour. 



In the case of other comets, the author suggests that the difficulty is one 

 of degree only, fiar the conditions are not known under which even a gas 

 permanent at the temperature of the earth could maintain sufficient heat 

 to emit light. 



The author states that some phosphorescent substances give spectra 

 which are discontinuous, but he gives reasons which would scarcely permit 

 us to consider cometary light to be of a phosphorescent character. 



The spectrum shows that the colour of this comet was bluish green. 

 Considerable difference of colour has been remarked in the parts of some 

 comets. Sir William Herschel described the head of the comet of 1811 

 to be of a greenish or bluish-green colour, while the central point appeared 

 of a ruddy tint. The same colours have been observed in other comets. 

 If carbon be the substance of some comets, this substance, if incandescent 

 in the solid state, or reflecting, when in a condition of minute division, the 

 light of the sun, would afford a light which, in comparison with that emitted 

 by the luminous vapour of carbon, would appear yellowish or approaching 

 to red. 



The author refers to the bearing of these results on certain cometary 

 phenomena, and on the apparent identity of the orbits of the periodical 

 meteors with those of some comets. 



