1889.] Nebula} and Stars with those of Comets and Aurora?. 33 



Here, again, it will be seen, there are many striking coincidences. 

 The hydrocarbon Anting at 431 and the hot and cool carbon flutings 

 at 468 — 474, 483, 517, and 519 are common to both. The flutings of 

 magnesium 500 and 521 and the flutings of lead and manganese 

 at 546 and 558 are also common. The iron fluting at 615 is not 

 seen in comets at ordinary temperatures, but since it was re- 

 corded in the Great Comet of 1882, it has been added, in brackets, 

 to the list of cometary flutings. The line at 426, which was seen in 

 Comet Wells, has also been added. It will be noted also that there 

 are apparent discrepancies ; some lines appearing only in comets and 

 others only in aurorae. The explanation of the absence of hydrogen 

 lines from comets which has already been given applies equally in 

 this case. As there is no repulsion in the aurora similar to that 

 exercised upon comets by the Sun, there is no reason for the absence 

 of hydrogen. In the aurora the hydrogen lines may also be produced 

 partly from aqueous vapour. The citron carbon flutings 561 and 564 

 have not been recorded in the aurora, although they are often seen 

 in comets ; their apparent absence from the aurora is probably because 

 they fall in the brightest part of the continuous spectrum, and are 

 consequently masked. 



The lines special to aurora? are 531, 535, 539, 606, and 630. 



III. Comparison between Comets and Bright-line Stars. 



In the Bakerian Lecture for 1888 I gave a complete discussion of the 

 spectra of bright-line stars, as far as the observations then went, and 

 the conclusion arrived at was that they are nothing more than swarms 

 of meteorites a little more condensed than those which we know as 

 nebulas. The main argument in favour of this conclusion was the 

 presence of the bright fluting of carbon which extends from 468 to 474. 

 This, standing out bright beyond their short continuous spectrum, 

 gives rise to an apparent absorption-band in the blue. The varying 

 measurements made by different observers may possibly have thrown 

 a little doubt upon the conclusion that the bright band was due to 

 carbon, but recent observations at Kensington have placed this 

 beyond doubt. Direct comparisons of the spectrum of 2nd Cygnus 

 with the flame of a spirit lamp were made by Mr. Fowler on 

 September 22nd, and these showed an absolute coincidence of the 

 bright band in the star with the blue band of carbon seen in the 

 flame. The 10-inch equatorial and a spectroscope having one prism 

 of 60° and two half-prisms were employed. On October 31st a 

 similar comparison was made with 3rd Cygnus, and this also 

 showed a perfect coincidence. It was found quite easy to get the 

 narrow spectrum of the star superposed upon the broader spectrum 

 of the flame, so that both could be observed simultaneously. 



VOL. XLV1I. D 



