GASEOUS SPECTRA UNDER HIGH DISPERSION. 435 



been long since agreed on the said places, quite closely enough for identifying 

 the phenomenon; and the Bezonian query of " C or CH" has never yet been 

 attempted to be answered by referring to any doubt about exact Spectrum place. 



PART III. 

 The CO Spectrum. 



This CO spectrum should symmetrically arise in a combination of Oxygen 

 with Carbon; just as CH represents Hydrogen joined to the same element; 

 and accordingly vacuum tubes with a trace of Carbonic Oxide (CO) give the 

 spectrum we have now to discuss, in a most marked manner and easily 

 recognisable character. 



In my former paper to this Society, I regret to say that I did, though with 

 expressions of considerable reserve, allow for the time, with the English 

 spectroscopists, that this spectrum might be one of pure Carbon, at a 

 temperature between lamp-flame and that of the Condensed Induction spark. 

 But I beg now to apologise for that error, to withdraw the name of " Tube 

 Carbon spectrum," — and to follow the teaching of Messrs Angstrom and Thalen, 

 who consider it to be the spectrum of the compound gas CO, (Carbonic Oxide) 

 and of that alone; for even if C0 2 (Carbonic Acid) be also in the tube, or even 

 occupy it entirely, one charge of its Oxygen remains ineffective, and exactly 

 the same visible spectrum, as that of CO alone, appears. 



Now this CO spectrum, from the materials of its origination, is one of 

 almost as extensive presence on the earth as CH; and has at first sight 

 something of its appearance. Yet they are two opposing and antagonising 

 principles at every step. 



Statical Differences. 



In small spectroscopes the CO spectrum is so far like the CH, in that it is a 

 spectrum of bands ; but it has many more ; so that while MM. Angstrom and 

 Thalen have shown in their Mesures Micrometriques two only for CH, they 

 show three for CO ; and in their general Index Map they have represented 

 8 principal, 5 secondary, and some 16 very faint indications of tertiary bands, 

 for CO ; but 5 only for CH. 



The 8 principal bands of CO reinforced by 2 bright ones of the secondary, 

 are, from their spectrum places, of the following notable grades of colour — 



(1) Eed, (6) Green, 



(2) Scarlet, (7) Blue, 



(3) Orange, (8) Indigo, 



(4) Yellow, (9) Violet, and 



(5) Citron, (10) Ultraviolet. 



