386 Nebular and Stellar Spectra. 



" A. In mixed feathers the barbs undergo some changes, 

 and the persistent barbules are much less modified than in 

 optical feathers. 



<C T>. In enamelled feathers the barbs though optical in 

 pigmentation, swell and colour themselves ; the barbules fall." 



We must, on a future occasion, return to M. Fatio's im- 

 portant paper. 



NEBULAE, AND STELLAR SPECTRA.— SOLAR OBSER- 

 VATION.— RED STAR.— PLANETS.— OCCULTATION. 



BY THE EEV. T. W. WEBB, A.M, E.E.A.S. 



The return of the glorious Orion Nebula to our evening 

 skies will always be a source of pleasurable anticipation to the 

 astronomical student : and now that its gaseous composition is 

 fully recognized, the possibility of change will be afresh induce- 

 ment to its attentive examination. It must still remain a 

 matter of strange and perplexing mystery, by what agency 

 such changes of figure or intensity can be produced in free 

 space ; but it will be admitted that there is less difficulty in 

 conceiving their existence in such a filmy mass, than among an 

 innumerable host of stars, where the presence of mutual 

 gravitation renders derangement of figure almost inconsistent 

 with permanency of existence : and hence the alterations of 

 figure and brightness already recorded or imagined, do not 

 now appear so incredible as they might in earlier days, nor so 

 probably if not certainly due to differences of instruments or 

 climates. We have already on several occasions* referred to 

 the opinions of eminent observers on this head, and we hava 

 now to add that renewed investigations have been in active 

 progress on the other side of the Atlantic. A considerable 

 time has elapsed since the late W. C. Bond published, in the 

 Memoirs of the American Academy, a finely executed figure of 

 this nebula, with a catalogue of the involved and adjacent 

 stars, which has been thought open to some exception. Otto 

 Struve,in particular, gave it as his opinion in 1857, that the latter 

 was " crowded with errors, and worked without any system," and 

 that the author had " expended more care on the graphical 

 representation of the nebula," without, as it should seem, in- 

 tending to rate even the diagram very highly. In consequence 

 of these remarks, a careful review was undertaken with the 

 noble instrument previously employed, an achromatic, by Merz, 

 * See Intellectual Obse&tee, iv. 258; v. 58; vii. 139; ix. 177. 



