494 



Profs. Liveing and Dewar. 



[June 10, 



alluded to is that described in the previous quotations, it is not a little 

 remarkable that Mr. Lockyer's experiments should so " entirely en- 

 dorse " what Watts himself has shown to have been in part erroneous. 



Lastly, we cannot allow Mr. Lockyer's assertion that Angstrom 

 and Thalen's conclusions " rest more upon a theory which has been 

 shown to be false since the labours commenced, and analogy, than 

 upon experiment," to remain uncorrected. Their conclusions are 

 eminently inductions from experiments carried on, as they say, during 

 several years, of which the most important are particularly described. 

 Many of the experiments which led up to their conclusions had been 

 previously published by Thalen in 1866 (" Arsskrift, Upsala "), in a 

 paper in which he correctly described and distinguished the spectra of 

 hydrocarbons, of oxide of carbon, and' of carbon respectively, and 

 besides described the spectrum of the spark between carbon poles in 

 nitrogen. This paper is an admirable sample of good experimental 

 work, and its perusal, together with the later paper of 1875, leaves 

 no doubt that, whatever theories they may have held, Angstrom and 

 Thalen relied mainly on experiment and observation to prove the 

 soundness of their conclusions. 



In conclusion, Mr. Lockyer introduces a reference to a former work 

 of ours on the magnesium-hydrogen spectrum, and to a theoretical 

 deduction regarding the interactions which might produce the cometic 

 spectrum, making the following remark :— 



"From what I have shown it will be clear that the consequences 

 drawn in the following paragraphs by Messrs. Liveing and Dewar 

 from the assumed hydrogen- carbon bands are entirely invalid." 



As this opens out a question entirely beside that in hand, de- 

 pending on the validity of the premises from which Mr. Lockyer draws 

 his conclusion, we prefer to deal with it when we discuss, in our next 

 paper, the spectra of carbon compounds and the experimental evidence 

 Mr. Lockyer has adduced in support of such assertions. 



VI. " On the Spectra of the Compounds of Carbon with Hydro- 

 gen and Nitrogen. No. II." By G. D. Liveing, M.A., 

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

 Jacksonian Professor, University of Cambridge. Received 

 May 27, 1880. 



In our last communication on this subject (ante, p. 152), we thus 

 summarised the results of our observations as to the " nitrocarbon 

 spectrum."* 



* In using this term we merely mean that we are dealing with a spectrum in- 

 variably associated with the presence of nitrogen and carbon in such conditions that 

 chemical union takes place, without any reference to the particular compound 

 produced. 



