1881.] on the Origin and Identity of Spectra. G75 



orange and red bauds shaded on the less refrangible side (i. e. in the 

 ojiposite way to the hydrocarbon bands), the four hydrocarbon bands 

 more or less develoiied, a group of seven blue lines, a group of two or 

 three faint blue (indigo) lines, then a group of six violet lines, and, 

 lastly, a group of four ultra-violet lines. When the cyanogen is burnt 

 in air, the hydrocarbon bands are less developed, and the three faint 

 indigo lines are scarcely visible, but the rest of the spectrum is the 

 same, only less brilliant. 



Pliicker and Hittorf * state that in the flame of cyanogen burning 

 in air under favourable circumstances, the orange and yellow groups 

 of lines characteristic of burning hydrocarbons are not seen, the 

 brightest line of the green group appears faintly, the blue group is 

 scarcely indicated ; but a group of seven fluted bands in the blue, 

 three in the indigo, and seven more in the violet, are well developed, 

 especially the last. When the flame was fed with oxygen instead of 

 air, they state that an ultra-violet group of three fluted bands appeared. 

 They notice also certain red bands with shading in the reverse direc- 

 tion, which are better seen when the flame is fed with air than with 

 oxygen. Other observers give similar accounts, noticing the brilliance 

 of the two series of bands in the blue and violet above mentioned, 

 and that they are seen equally well in the electric discharge through 

 cyanogen. 



Angstrom and Thalen, in a memoir "On the Spectra of Metal- 

 loids,"! contend that the channelled spectra of the hydrocarbon and 

 cyanogen flames are the spectra respectively of acetylene and cyanogen, 

 and not of carbon itself, and that in the flame of burning cyanogen we 

 sometimes see the spectrum of the hydrocarbon superposed on that of 

 the cyanogen, the latter being the brighter ; and that in vacuum 

 tubes containing hydrocarbons the cyanogen spectrum observed is 

 due to traces of nitrogen. 



No chemist who remembers the extreme sensibility of spectro- 

 scopic tests, and the difficulty, reaching almost to impossibility, of 

 removing the last traces of air and moisture from gases, will feel any 

 surprise at the presence of small quantities of either hydrogen or 

 nitrogen in any of the gases experimented on. 



Mr. Lockyer J obtained a photograph of the sj^ectrum of the 

 electric arc in an" atmosphere of chlorine, which shows the series of 

 fluted bands in the ultra-violet, on the strength of wliich he throws 

 over the conclusion of Angstrom and Thalen, and draws inferences 

 regarding the existence of carbon vapour above the chromosphere in 

 the coronal atmosphere of the sun, which, if true, would be contrary 

 to all we know of the properties of carbon. 



The conclusions of Angstrom and Thalen have been much 

 strengthened by the results of a series of observations carried out by 

 Professor Liveing and myself. 



* ' Phil. Trans.' 1865. t ' Nova Acta, Roy. Soc. Upsala,' vol. ix. 



X 'Proc. Rov. Soc' vol. xxvii. p. 308. 

 Vol. IX. (No. 74.) 3 a 



