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



The spectrum of this nebula has hitherto been regarded as a per- 

 fectly continuous one, but the observations referred to show that 

 there are some parts brighter than others. The spectrum is almost 

 entirely wanting in red and yellow light. In the green there are two 

 maxima, the brightest of which is at wave-length 517, as near as 

 could be determined with the wide slit which it was necessary to 

 employ ; the other maximum is near 546. One of the observers, 

 Mr. Fowler, made six independent measures of the maxima on 

 November 20th, and got very nearly the same result each time, com- 

 parison being made with the spectrum of a bunsen, and the spectrum 

 of chloride of lead at the temperature of the bunsen. The measure- 

 ments were repeated on November 27th, with the same result, and 

 on this occasion they were confirmed by another observer, Mr. Coppen. 

 Another brightness near 474, as determined by comparison with the 

 bunsen burner, was also suspected, but it was not so easy to measure 

 as the others. 



My suggestion as to the origin of this spectrum is that it is the in- 

 tegration of very slight continuous spectrum, carbon fluting radiation, 

 and the absorption of manganese (558) and lead (546). The citron 

 band of carbon masks and is masked by the manganese fluting, and 

 the absorption fluting of lead causes by contrast the apparent bright- 

 ness at 546. The brightest maximum is no doubt the brightest 

 fluting of carbon at 517, and the one in the blue, which was sus- 

 pected, is probably the blue carbon group 468 474. 



If these observations are confirmed this nebula is at present at the 

 same stage of condensation as Comet I, 1868, on April 29th (p.p. 

 April 20th), which must be regarded as a pretty advanced cometary 

 stage, seeing that it was observed so near perihelion and that the peri- 

 helion distance was small. 



The discussion of the observations of Nova Andromedae, which is 

 not yet completed, shows that there were bright lines in exactly 

 the same positions as the brightnesses which have now been de- 

 termined in the nucleus of the nebula. The appearance of the Nova 

 was therefore probably due to increased temperature due to collisions 

 taking place between the sparser outliers of the swarm composing 

 the nebula and the external swarm which came in contact with them. 

 The view of the Nova's probable connexion with the nebula is there- 

 fore greatly strengthened by this inquiry.] 



[Note added January 8, 1889. If it be conceded that the tails of 

 comets are in part composed of hydrogen and gaseous compounds of 

 carbon, an explanation seems to be afforded of many recorded pheno- 

 mena, among which may be mentioned 



I. The absence of carbon and oxygen from the sun ; 



