the Spectra of Carbon and Hydrocarbon, 547 



of the source, and the origin of certain new lines and bands 

 which have been recorded photographically. 



The "Swan" spectrum, characteristic of the flame of 

 hydrocarbons, consists of the well-known groups of flutings 

 in the yellow, green, and blue attributed to the element 

 carbon, as well as some bands of more complicated structure 

 in the violet which are ascribed to hydrocarbon. This 

 spectrum is given brightly and with purity by the base of 

 the flame of a Meeker gas-burner (coal-gas burning in air). 



Other flutings of similar structure and obviously be- 

 longing to the same system of bands can be distinguished 

 in the red-orange region of the flame spectrum ; but these 

 are very faint and difficult to photograph. In the spectrum 

 of the electric arc between carbon poles in air, the yellow, 

 green, and blue " Swan " bands are reproduced brightly 

 with the addition of the intense fluted bands in the violet 

 and ultra-violet which are ascribed to cyanogen since 

 nitrogen must be present for their production. In the 

 absence of hydrogen, however, the hydrocarbon bands do 

 not appear. 



In the red and orange regions of the carbon arc spectrum 

 we find very complex series of lines in which cyanogen is 

 represented by a number of flutings *, but the bands of 

 carbon, faintly visible in the flame spectrum, are nevertheless 

 obscured and inconspicuous, their heads being traceable only 

 with some difficulty. 



In the " Swan " spectrum, carbon is represented by the 

 following groups of flutings -j- ; — 



XX. 



ed-orange 

 Group. 



6191-1 



Yellow 

 Group. 



5635-4 



Green 

 Group. 



5165-3 



Blue 

 Group. 



4737-2 



Violet 

 Group. 



4381-9 



6121*8 



5585-5 



5129-4 



4715-3 



4371-3 



6059-9 



5540-9 



5101-0 



4697-6 



4365-0 



6005-1 



5501-9 



5081-9 



4684-9 (' 



'the th re 



5958-2 



5472-7 









An attempt was made to apply the electrical conditions of 

 the arc discharge to the products of the flame in which 

 carbon was in the process of changing its chemical com- 

 bination. 



* " The Less Refrangible Spectrum of Cyanogen, and its Occurrence 

 in the Carbon Arc," Fowler and Shaw, Proc. Roy. Soc. A, vol. Ixxxvi. 

 (1912). 



+ See also ' Index of Spectra,' W. Marshall Watts, Appendix V., 

 pp. 67, 08. 



2 P 2 



