490 



Profs. Liveing* and Dewar. 



[June 10,. 



V. " Note on the History of the Carbon Spectrum." By G. D. 

 LlVElNG, M.A., F.R.S., Professor of Chemistry, and J. 

 Dewar, M.A., F.R.S., Jacksonian Professor, University of 

 Cambridge. Received May 26, 1880. 



In a "Note on the Spectrum of Carbon," read before the Society on 

 April 29, 1880, Mr. Lockyer has in the first place alleged that we have 

 advanced within a very short period inconsistent opinions as to 

 spectra of compounds of carbon ; he has next implied that we have- 

 given an unfair representation of the history of the carbon spectrum, 

 and, lastly, has directly challenged the correctness of some of the con- 

 clusions we have drawn from our experiments. We propose in this 

 paper to reply to him on the historical questions, and in another paper 

 to deal with the experimental evidence which he has produced in con- 

 travention of our conclusions. 



That the inconsistency alleged has not really existed in our opinions, 

 will be seen by any one who reads the first passage referred to as it 

 appeared in the published " Proceedings of the Society " (vol. xxx, 

 p. 87), which stands as follows: — ■ 



" The well-nigh impossible problem of eliminating hydrogen from 

 masses of carbon, such as can be employed in experiments of this 

 kind, proves conclusively that the inference drawn by Mr. Lockyer as 

 to the elementary character of the so-called carbon spectrum from an 

 examination of the arc in dry chlorine, cannot be regarded as satis- 

 factory, seeing that undoubtedly hydrogen was present in the carbon* and 

 in all probability nitrogen in the chlorine.' 1 '' 



Mr. Lockyer has quoted the confidential, uncorrected, proof instead 

 of the published paper which had been issued before Mr. Lockyer's 

 paper was read. In the published paper a clause, accidentally omitted 

 before, and no way altering the general drift of the passage, had 

 been inserted to make the sense clearer. The paper from which he 

 quotes deals with the chemical interactions taking place in the 

 arc between the matter of the poles and the constituents of the 

 surrounding atmosphere. It is there demonstrated that specially 

 purified carbon poles continue to produce in dry air cyanogen com- 

 pounds, and that hydrogen always forms an essential ingredient of 

 such poles. No reference was made in this paper to the specific 

 origin of any fmtings in the spectrum of the arc, the sole question 

 under consideration being the possible existence of carbon compounds 

 in the electric arc taken in dry chlorine, on the non-existence of which 

 Mr. Lockyer bases his proof of the elementary character of the carbon 

 spectrum. That part of the paper from which the quotation is taken 

 related particularly to the combination of nitrogen with the carbon of 



* Mr. Lockyer haying italicized the former half of the last clause, we italicize 

 what he chose to omit. 



