﻿Flames of Gases containing Carbon. 213 



5 Middle of a broad black line. 



2 Middle of a lavender- grey band"*. 



1 End. 



This peculiarity of the spectrum, which imparts to its most 

 refrangible part a character of quite an opposite kind to that of 

 the remaining parts, could never be distinctly observed in the 

 spectrum of coal-gas, although in the latter also fine black lines 

 are perceptible in the dark-violet end. In other respects this 

 spectrum agrees perfectly (as has been already stated) with that 

 of coal-gas ; for the appearance of a fourth line in the group 7, 

 as well as of a group of four faint lines between y and S, to 

 which the values 186, 183, 181, and 170 of our scale corre- 

 spond, in no way affects the distinctive type of this spectrum, 

 and is only seen under circumstances especially favourable to 

 the observation. 



The agreement which is indubitably apparent on a comparison 

 of the spectra which are obtained by a flame of spirit of wine, 

 by a flame of a wax-light in the blue part, by coal-gas ignited 

 with atmospheric air or oxygen, and by olefiant gas with oxygen, 

 justifies the assertion that it is entirely the greater or smaller 

 quantity of the luminous particles combined with the higher or 

 lower temperature that produces the gradually seen difference 

 in these spectra, and that all must be in themselves of the very 

 same quality. Whether the luminous particles of disintegrated 

 carbon are in the condition of vapour, as has been repeatedly 

 assumed, and whether the opinion first expressed by Attfield f, 

 that the spectra of all combinations of carbon are to be consi- 

 dered as spectra of carbon itself, will be confirmed, or whether 

 every gas containing carbon has its own peculiar spectrum, — 

 these are questions which, in regard to the spectra of flames, 

 the present state of our knowledge does not enable us to decide. 

 If, however, we are careful to use only facts in our discussions 

 of the problem, and remember that the presence of carbon in a 

 gaseous condition is only an hypothesis, and even those cases in 

 which this hypothesis appears justifiable, as in Geissler's tubes, 

 manifest relations of so different a nature that reasoning from 

 them is an inadmissible process — and if, moreover, we take 

 into consideration the great difference shown by the spectra of 

 cyanogen and carbonic oxide compared with those of coal-gas 

 and other kindred substances, we shall not be able to adopt the 

 view that all spectra of flames of compounds of carbon can be 

 regarded as spectra of carbon itself. In addition to this, the in- 



* The bright lines of the most refracted group of the cyanogen-spec- 

 trum, which also are of a lavender-grey colour, correspond precisely with 

 this position. 



t Edinburgh Phil. Trans, vol. xxii. p. 224. 



