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



I found thafc the mixture of continuous band spectrum in different 

 parts was very unequal, and, further, that the apparently continuous, 

 spectrum changed its character and position of maximum. Over some 

 regions it was limited almost to the region between the less refrangible 

 bands. 



I wrote at the time : 



" It is more than possible, I think, that the cometary spectrum, 

 therefore, is not so simple as it has been supposed to be, and that the 

 evidence in favour of mixed vapours is not to be neglected." 



Comet III, 1881. 



The perihelion passage of this comet occurred on June 16th. I 

 have already remarked that Copeland* observed on June 25th a dark 

 band at 567'9 in this Comet, in addition to the hot carbon radia- 

 tion. This band was probably due to lead at 568, the first band at 

 546 being masked by the hot carbon. Manganese absorption was also 

 indicated on the same date. On June 25th the spectrum of this comet 

 was photographed by Huggins, and the carbon B group of fluting s 

 was stated to have been seen, giving indications of a relatively high 

 temperature. As the comet receded from the sun other phenomena 

 were observed. On June 27 magnesium at 520 was detected by 

 Hasselberg ; manganese absorption was again indicated in Copeland's 

 observations on Jane 28, and manganese radiation on June 29 and 

 July 27. I have already had occasion to refer to these two conditions 

 (p/193). 



No observations were made on the comet after July 27, or the hot 

 and cool ca-rbon flutings would doubtless have been recorded alone. 

 Oarbon radiation is indicated in all the observations that were made 

 from June 25 to July 27. 



It should also be noted that hydrocarbon at 431 was observed on 

 June 28th, by Copeland ; but neither before nor after this date was 

 hydrocarbon recorded. The reason probably is that the band is too 

 far in the violet to be very manifest. Copeland recorded it as " a 

 bright line, common to spirit-lamp and comet," and hence there can 

 be no mistake as to its identity. 



Brorsen's Comet. 



The observations of this comet at its appearance in 1868, made by 

 Secchif between the 23rd and 27th of April, 1868, and by HugginsJ 

 between April 2yth and 13th May, 1868, perihelion passage occurring 

 on April 20, 1868, differ very considerably. 



Secchi observed flufcings at 473, 512, and 553. The first of these 



* 'Copernicus,' vol. 2, p. 225. 



t ' Comptes Eendus,' vol. 66, p. 882. 



J ' Roy. Soc. Proc.,' vol. 16, p. 386. 



