14 



SOME CONTINUED OBSEEYATIONS ON THE YAEI- 

 ABLE STAE -n AEGUS, AND THE SUEEOUNDING 

 NEBULA. 



[Eead April 14th, by Francis Abbott, F.E.A.S,, &c.] 



Laid on the table a dra-wing of tlie object taken at three 



different periods, from 1834-7 up to February, 1868, the 

 monographs of Sir John Herschel, taken at the Cape of Good 

 Hope, and a record of the star from the time of Halley in 

 1677. 



It will be remembered by some members of the society, who 

 are interested in astronomical discoveries, that at the monthly 

 meetings held in June, 1863, and March, 1865, some notes 

 were read on the variable star -n Argus, and the surrounding 

 nebula. At about the same time information connected with 

 the subject was forwarded to the Eoyal Astronomical Society, 

 who published it in their proceedings. This communication 

 led to discussions on the subject in many scientific journals, 

 and eventually to notices in standard works on astronomy, in 

 some of which further observations and information have been 

 solicited. It is to answer this enquiry that the original copy 

 of this drawing and description have been prepared. Before 

 proceeding with the notes on the present appearance of r; Argus, 

 and its surrounding nebula, I purj^ose reading one or two 

 paragraphs from recent publications in order to shew 

 the interest which this object has excited among astrono- 

 mers in Europe, from previous communications which have 

 been sent ; and it will appear clear to the present meeting by 

 an inspection of the drawing, that fluctuations to a consider- 

 able extent have taken place since those articles were written. 

 There is also reason to believe that other portions of the via 

 lactea, as well as the nebula in question, are subject to motions 

 by a system of acting forces calculated to produce them, and 

 such as may offer opportunities for future observations. 



Descriptive Astronomy. — Clarendon Press Series. — " The foregoing 

 observations may be said to have relation to objects of a minor character, 

 but we are not without at least one example of an important nebula under- 

 going peculiar changes. The great nebula in Argus, when observed by- 

 Sir J. Herschel in 1838, contained within its area a vacuity of considerable 

 size. The star 77, then of the 1st magnitude, was situated in the most 

 dense part of the nebula, and was completely encompassed by nebulous 

 matter. In 1863, we learn from Abbott, of Hobart Town, the star was 

 entirely free from nebulosity, and only of the 6th magnitude. The ob- 

 server also states that the outline of the vacuity materially different from 

 the representation given by Herschel. Mr. E. B. Powell, of Madras, not 

 only confirms these remarks generally, but also says distinctly that the 

 nebula as a whole has varied much in brilliancy during the time it has 



