1880.] Mr. J. N. Lockyer. On the Spectrum of Carbon, 461 



were absent, and from the fact that the mixed product (for only a 

 portion of the 14 mgrms. was clear diamond) contains nitrogen, I am 

 inclined to believe that it is by the decomposition of a nitrogenous 

 body, and not the hydrocarbon, that the diamond is formed in this re- 

 action. The experiments are, however, too few, and the evidence too 

 vague, to draw any conclusions, as there are even very few negative 

 experiments from which anything can be learned, most of the results 

 being lost by explosion. I intend, when my other work — which I laid 

 aside for the diamond experiments — is finished, to begin a series of 

 experiments on the decompositions of carbon compounds by metals, to 

 find whether a more easily controlled reaction may not be discovered. 



VII. " Further Note on the Spectrum of Carbon." By J. 

 Norman Lockyer, F.R.S. Received May 11, 1880. 



The preliminary discussion of a considerable number of photo- 

 graphs of the spectra of various carbon compounds has brought to 

 light a relationship which I think may be worthy of notice in the 

 Proceedings ; it was noticed orally in connexion with the paper read 

 before the Society on April 29th. 



A comparison of the photographs of the various carbon compounds 

 observed under various conditions enabled us to isolate the lines in the 

 blue and ultra-violet portions of the spectrum (wave-lengths 4300- 

 3800). 



In this manner the constant lines seen in the photographs of the 

 spectra of CC1 4 , C 10 H 8 , CN, CHI 3 , CS 2 , C0 2 , CO, &c, have been 

 mapped, and the coincident lines and flutings thus marked. 



The phenomena thus seen with more or less constancy are a blue 

 line, with a wave-length of 4266 ; a set of blue flutings, extending 

 from 4215 to 4151; and another set of ultra-violet flutings, which 

 extend from 3885 to 3843 (all approximate numbers) . 



Tig. 1. 



Action of three different temperatures on a hypothetical substance, assuming three 

 stages of complete dissociation. 



Highest 

 temp. 



Interme- 

 diate. 



Lowest 

 temp. 



In a photograph of the spectrum of the electric arc (with a weak 



