370 Dr. W. M. Watts on the Spectrum of Carbon. 



terval between the lithium- orange line (6101) and the least- 

 refrangible sodium-line (5895). 



The reference-lines employed were, as far as available, the 

 Fraunhofer lines of the solar spectrum, and the lines of the 

 spark-spectra of magnesium, lead, air, antimony, cadmium, and 

 zinc. 



The results are given in the following Table. Column I. 

 gives the designations of the lines measured as given in my 

 1 Index of Spectra -, ' column II. the wave-lengths as now de- 

 termined in tenth-metres ; column III. the number of obser- 

 vations ; column IV. the difference of the highest and lowest 

 results from the mean result. 



I. 



II. 



III. 



IV. 



7 



'580 

 60-0 



< 61-5 



630 



,64-5 



5634-7 

 5585-5 

 5542-3 

 5503-5 

 5478-4 



11 



7 

 2 

 1 



1 



+ 1-3,-1-4 

 +05, -0-6 

 +0-0, -o-o 



T75-0 

 8 {770 



[79-3 



5165-5 

 5130-4 

 51000 



4 

 7 

 2 



+0-3, -0-5 

 + 10,-21 



+0-8, -0 8 



6« 



' 97-0 



98-5 



100 



101-5 



101-7 



4739-8 

 4717-2 



4698-4 

 4684-2 

 4677 



4 

 5 

 4 

 2 

 1 



+2 2, -3-6 

 +2-1, -3-3 

 + 1-5, -3 2 



+ 1-8,-1-8 



The lines most exactly determined are those whose wave- 

 lengths are 5165*5 and 5585*5. 



It may be well to repeat here that this spectrum is the spec- 

 trum of carbon, and not of a hydrocarbon or any other compound 

 of carbon. That it is so is proved by the fact that it is common 

 to compounds of carbon with oxygen, with hydrogen, and with 

 nitrogen (Phil. Mag. S. 4. vol. xxxviii. p. 249) ; and this evi- 

 dence does not rest oaly upon the use of vacuum-tubes, the 

 results obtained from which are confessedly open to doubt. 

 The spectrum is not only obtained from the flame of olefiant 

 gas and cyanogen or oxygen, but also from the electric spark 

 taken directly in a stream of cyanogen (or carbonic oxide) at 

 the ordinary pressure. 



