1889.] of the various Species of Heavenly Bodies. 195 



due to the low-temperature magnesium fluting at 500. On the 29th 

 of May the spectrum of the comet was again observed by Cope- 

 land and Lohse, and the identity of the bright line in the yellow 

 with the D line placed beyond doubt. On the preceding day a Dun 

 Echt circular had announced the discovery as follows : " The 

 spectrum of the nucleus of Comet Wells deserves the closest attention, 

 as it shows a sharp bright line coincident with D, as well as strong 

 traces of other bright lines, resembling in appearance those seen in 

 7 Cassiopeise and allied stars." 



Dr. Huggins succeeded on. the 31st of May in photographing the 

 spectrum of this comet, and, as was to be expected, could detect no 

 trace of the ultra-violet carbon fluting which was seen in his photo- 

 graph of Comet 6, 1881. I have already had occasion to refer to 

 this photographed spectrum.* 



On the same day the spectrum of this comet was observed by 

 Maunder, Copeland, Vogel, and others. The most complete record 

 is that made by Copeland and Lohse. They observed " a bright part; 

 line (?) " at wave-length 614*1, for which the reading on the follow- 

 ing day gave 615'7. There can be little doubt that this was a con- 

 trast band due to the absorption of the low-temperature iron fluting 

 at 615. At the same time there was a maximum brightness in the 

 green at wave-length 501 '7, caused most probably by the radiation 

 of the magnesium fluting at 500, in addition to the continuous 

 spectrum. 



" A bright part, a maximum " of which the wave-length recorded 

 on May 31st was 543'6, and on the following day 546'8, was due 

 in all probability to absorption by the lead fluting at 546, as I have 

 already explained. It was on this night (May 31st) that Vogel iirst 

 observed and identified the bright sodium line. " When I examined 

 the spectrum, on May 31st," he writes, " I was greatly surprised by a 

 line in the yellow of great intensity. Measurements and comparisons 

 seemed to identify this line with the sodium line. Yesterday, June 

 1st, several measurements were made by Dr. Miiller, Kempf, and 

 myself, which showed an agreement of the bright line in the spectrum 

 of the comet's nucleus with the D lines ; considering the dispersion 

 used this agreement must be called an absolute one. The continuous 

 spectrum extended from about C to deep in the violet. Besides the 

 bright yellow line traces of bright bands were present, perhaps also 

 some dark absorption-lines, "t Writing later, he describes the 

 observations of June 2nd thus : " The bright line was, not only in 

 the spectrum of the nucleus, but also in the parts of the comet near 

 to the nucleus, distinctly visible. Besides this, several more bright 

 bands could be seen, which stood out more distinctly when the slit of 



* ' Koy. Soc. Proc.,' vol. 43, p. 130. 

 t ' Astr. Naehr.,' No. 2434. 



