250 Dr. W. M. Watts on the Spectra of Carbon. 



Plucker and Hittorf, Phil. Trans. 1865, p. 1. 



Morren, Ann. de Chim. et de Phys. 1865, vol. iv. p. 305. 



Lielegg, Phil. Mag. S. 4. vol. xxxiv. p. 302; vol. xxxvii. p. 208. 



Deville, Leqons sur la Dissociation, and Phil. Mag. S. 4. vol. 

 xxxvii. p. 111. 



Wiillner, Phil. Mag. S. 4. vol. xxxvii. p. 405. 



Frankland, Proc. Roy. Soc. vol. xvi. p. 419. 



I select as the typical form of the first carbon- spectrum that 

 obtained when olefiant gas and oxygen are burnt together in an 

 oxyhydrogen blowpipe-jet. The name thus obtained exhibits a 

 central cone of intense green, which, examined by the spectro- 

 scope, gives the spectrum first obtained by Swan, and ascribed 

 by Attfield to the vapour of carbon. The spectrum which is 

 drawn, Plate I. fig. la, is one of the most beautiful which can be 

 imagined, and consists of five groups of lines — a in the red, <y in 

 the greenish yellow, $ brilliant emerald-green, 6 in the blue, and 

 / violet. 



Group a* contains five lines, of which the third is the bright- 

 est. 7 contains seven, of which the least refracted is the brightest, 

 and each succeeding line is less brilliant than the one before ; so 

 that the group rises sharply out of darkness on the left, and 

 fades gradually away on the right. The group 8, which con- 

 tains four lines, presents the same gradation of intensity : e con- 

 tains four lines of nearly equal intensity, the fourth being double ; 

 and/ consists of a broad band, then a fine bright line, and then 

 a band fading away on the most refracted side. When the spec- 

 trum is obtained very brightly, there may be observed in addition 

 six very fine bright lines of equal intensity, which gave the 

 readings 86, 87'5, 89, 91, 93, 95. The band 128-133 is also 

 seen to be shaded by a large number of nearly equidistant fine 

 dark lines; and the least refrangible band of the group/ (121- 

 126) is resolved into lines. 



This spectrum may be obtained from the flame of any hydro- 

 carbon, though in many cases, owing to the faintness of the 

 spectrum, only some of the groups can be recognized. In the 

 flame of an ordinary Bunsen burner 8 and e are easily seen, y and 

 / are much fainter, and the red group cannot be detected. 



This spectrum is proved to be that of carbon, inasmuch as it 

 can be obtained alike from compounds of carbon with hydrogen, 

 witli nitrogen, with oxygen, with sulphur, and with chlorine. 

 I have obtained it, namely, from each of the following com- 



* This is the group described as new by Professor Lielegg, Phil. Mag. 

 March 1869. It is true, as he notes, that Dibbits strangely omits it, and 

 that Plucker and Hittorf give only three lines ; but the group of five lines 

 is given by Morren, and they are distinctly figured in the drawing to ray 

 paper on the Bessemer-spectrum in the Philosophical Magazine for De- 

 cember 1867. 



