188 Mr. J. N. Lockyer. On the Classification [Jan. 10, 



of this comet were made between May 20th and June llth, the 

 perihelion passage occurring on June 10th. 



The comet gave indications of a comparatively high temperature 

 during all of this interval, so that the derivation of the line from the 

 fluted spectrum of carbon, or vice versa, cannot be traced. 



In addition to this evidence of the existence of carbon in comets, 

 we have further evidence afforded by Dr. Huggins's photograph of the 

 spectrum of Comet III, 1881,* taken on June 24th, the perihelion 

 passage occurring on June 16th. Besides the dark line spectrum to 

 which I have previously referred, the photograph shows three groups 

 of apparent bright lines. Measurements of the two strongest lines in 

 the most refrangible group gave, according to Dr. Huggins, 3883 and 

 13870 as the wave-lengths. Dr. Huggins says (p. 2) : " The less re- 

 frangible line is much stronger, and a faint luminosity can be traced 

 from it to a little beyond the second line at 3870. There can be, 

 therefore, no doubt that these lines represent the brighest end of the 

 ultra-violet group which appears under certain conditions in the 

 spectra of the compounds of carbon. Professors Liveing and Dewar 

 have found for the strong line at the beginning of this group the 

 wave-length 38827, and for the second line 3870'5. . 



" I am also able to see upon the continuous solar spectrum, a 

 distinct impression of the group of lines between G and h which is 

 usually associated with the group described above. My measures for 

 the less refrangible group give a wave-length of 4230, which agrees as 

 well as can be expected with Professors Liveing and Dewar's measures 

 4220." 



In addition to the two groups of bright lines above mentioned, a 

 third and fainter group between h and H is shown by Dr. Huggins. 

 On the lithograph which accompanies the paper these lines are shown 

 at approximate wave-lengths of 4059, 4052, 4044, and 4038, but no 

 origin is suggested for them. 



Messrs. Liveing and Dewar have attributed the two groups first 

 mentioned to cyanogen ; but my own researches, which are still far 

 from complete, have not convinced me that this view is correct. I 

 may state, and here Messrs. Liveing and Dewar's observations agree 

 with my own, that the most characteristic cyanogen group is one 

 beginning at about 461 ; and since there is no trace of this in the 

 photograph, it does not seem likely that the groups seen can be taken 

 as proving the existence of cyanogen. 



In a paper which I communicated to the Royal Society in 1880f I 

 described the two groups of lines, or rather flutings, which are 

 referred to in Dr. Huggins's paper, and I also gave their wave-lengths. 

 I have since found that under certain conditions other compounds of 



* ' Koy. Soc. Proc.,' vol. 33, p. 2. 

 f ' Eoy. Soc. Proc.,' vol. 30, p. 461. 





