PROGRESS OF ASTRONOMY FOR 18i)l AND 1892. 683 



sky. He finds thus that tlie st;irs of the Sirii(<i ty])e occur cliietly in the 

 Milky "Way, whilst stars ot other types are fairly divided over the sky. 



Now stars of the Sirins ty]>e are very white stars, very rich ri'lative 

 to other stars in the rays which act most stioiii;ly on a iilioto,ur;i])hic 

 plate. Here then is the explanation of the results of our photoj^raphic 

 star-charting, and of the <liscor(lance between the photographic and 

 visual magnitudes m the Milky Way. 



The results of the Cape charting further show that it is not alone to 

 tlie brighter stars that this discordance extends, but it extends also, 

 though in a rather less degree, to the fainter stars of the Milky Way. 

 Therefore we may come to the very remarkable cinielusion that the 

 Milky Way is a thing apart; and that it has been developed perhai)s in 

 a difterent manner, or more probably at a different and probably later 

 ej)och from the rest of the sidereal universe.* 



NEBT L.E. 



In a paper by Prof. Keeler, comnninicated to the lioyal Society by Dr. 

 Huggius on March 19, 1891, the question of the position of the chief 

 nebular line seems to be definitely settled. Prof. Keeler has not only 

 made a series of sixteen complete measures, obtained on eleven nij^hts, 

 of the chief line in the spectrum of the Orion nebula, thus defining its 

 apparent position when corrected for the earth's motion, as X 5()0().22 ± 

 0.014, but has supplemented these by ten measures of the green iiydro- 

 gen line on seven nights. The latter show the nebula to be moving 

 relatively to the solar system with a motion of + 10.7 ± 1.0 miles per 

 second, and oblige us to fix the true position of the chief line at ^- 5005.93. 

 The chief line is therefore 0.13 tenth meter more refrangible than the 

 lower edge of the magnesium fluting, and as it has no resemblance to 

 a fluting in appearance, and as flutings and lines of magnesium, which 

 could not fail to appear at the same time with the fluting at A 5006.36 

 are entirely absent from nebular spectra, the incorrectness of the view 

 that the nebular line is the remnant of the magnesium fluting appears 

 to be demonstrated. 



Mr. Rurnham has made a set of measures of the nebula in the 

 Pleiades close to the star Merope. He remarks that it is one of the 

 most singular and interesting objects in the heavens. With respect 

 to its nearness to a bright naked-eye star (the distance between the 

 centers is less than 40") it is unique. There may be other examples, 

 but certainly no other has ever been discovered, and this close asso- 

 ciation of a faint nebula and one of the prominent stars of the Pleiades 

 is an interesting fact, whether such association is accidental or other- 

 wise. The accurate measures made by Mr. Burnhani and Mr. Barnard 

 will enable this point to be ascertained when others shall have been 

 made sometime hence, and it will be p(>ssible to determine by comi)ar- 

 ison whether the new nebula is drifting in space with Merope and the 

 other stars of this famous group. We have, of course, many examjjles 

 of large stars involved in widely diffused and extended nebulous masses, 



"Publications of the Astrouoinical Society of the Pacific, 19. 



