1880.] 



Note on the Spectrum of Carbon. 



341 



Liveing and Dewar, are due to hydrocarbon, and the set of flutings 

 which is reversed in the snn, and ascribed by Messrs. Liveing and 

 Dewar to cyanogen, also appear in a photograph of the violet end of 

 the spectrum. On connecting a Leyden jar with the coil and then 

 passing the spark the flutings almost entirely vanish and the line 

 spectra of chlorine and carbon take the place of the flutings without 

 either a line of hydrogen or a line of nitrogen being visible. 



As a long experience has taught me that these tubes often leak 

 slightly at the platinums after they are detached from the pump, I 

 took the occasion afforded by a visit of Dr. Schuster to my laboratory 

 while the experiments were being made to get my observations con- 

 firmed. He has been good enough to write me the following letter, 

 and to allow me to give it here : 



"March 21. 



" My dear Lockyer, — The following is an account of the experiment 

 which I saw performed in your laboratory on Monday, March 15 : — 



"A tube containing carbon tetrachloride was attached to the 

 Sprengel pump. As exhaustion proceeded the air was gradually dis- 

 placed by the vapour of the tetrachloride. The electrodes were a few 

 millimetres apart. If the spark was taken without a condenser in the 

 vapour the well-known carbon bands first discovered by Swan in the 

 spectrum of a candle were seen with great brilliancy ; I also saw the 

 blue band which you said was identical in position with one of the 

 blue bands seen in the flame of cyanogen or in the spectrum of the 

 electric arc. When the condenser and air-break were introduced this 

 spectrum gave way to a line spectrum in which I could recognise the 

 lines of chlorine. The lines of nitrogen -were absent, not a trace of the 

 'principal double line in the green being seen. The hydrogen line H<z(C) 

 was faintly visible when I first observed the spectrum, but it got 

 gradually weaker and finally disappeared altogether. When this line 

 ivas no longer visible the condenser ivas taken out of circuit again, and 

 the same carbon bands ivere seen as before. These bands, therefore, 

 show themselves with great brilliancy when a strong and powerful 

 spark does not reveal the presence either of hydrogen or nitrogen. 



" (Signed) Arthur Schuster." 



This result, which entirely endorses the work of Attfield and Watts, 

 has been controlled by many other experiments. I have also repeated 

 Morren's experiment and confirmed it, and I have also found that the 

 undoubted spectrum of cyanogen is visible neither in the electric arc 

 nor in the surrounding flame. 



I hope to show in the complete paper that the various difficulties 

 which have always been acknowledged to attend observations of this 

 substance may in all probability be due to the fact that the sets of 

 carbon flutings represent different molecular groupings of carbon, in 



