On the Nebula around JEta Argus. 19 



enclosed space, and some remarkable minor details at a point 

 about 17 seconds preceding and 80 seconds north of Eta, which 

 are changing rapidly. 



It thus appears that up to the end of 1870 no one had complied 

 with Sir John Herschel's request, but that all the observers had 

 confined their drawings to the nebulous mass in which the 

 lemniscate is situated, and neglected the branches. My first in- 

 tention was to do the same, for the difficulty in representing such 

 a complicated nebula is very considerable, but I noticed such 

 changes in the branches that I was induced to examine carefully 

 all that is included in the Cape drawing, and to attempt to repre- 

 sent the greater part of it. 



I determined last year to examine this object, believing that 

 when such a subject is under discussion, all who have the means 

 of furnishing information should do so, and because the Sydney 

 refractor is in defining and light-gathering power nearer to the 

 reflector with which the Cape drawing was made, than any which 

 has since been directed to the object. 



From many trials on close double stars, I find this instrument 

 quite equal in defining power to the 18-inch reflector, but of 

 course not equal to it for revealing minute stars. 



Unfortunately, in August last Eta Argus was too low down to 

 admit of any satisfactory observations, and I was obliged to defer 

 it to January this year ; when I took every favourable oppor- 

 tunity of observing it, and completed the drawing early in March. 

 The observations were taken after the object had attained an alti- 

 tude of 50° up to 64°. 



Of the 108 stars in my list I was able to identify 104 with 

 those in the Cape list ; of the remaining 4 — one, No. 25, is very 

 small, and forms part of a triangle close to Eta, in 1834-8 it was 

 probably hidden by the light of Eta ; another, No. 32, is in the 

 dark enclosure, and very small indeed, I am inclined to think it 

 is variable, from comparisons made with four faint ones near Eta ; 

 another. No. 68, must, I think, have appeared since 1834-8, for it 

 is now ' a conspicuous star, about 10 magnitude, and I am 

 convinced could not have escaped Sir John Herschel's wonder- 

 fully accurate survey ; and the fourth. No. 92, I have since found 

 is No. 142 H, an error of 10 s. having occurred in recording the 

 right ascension, which should be 135 s. instead of 145 s. 



Of the magnitudes of the stars, it is beyond doubt that several 

 of those in the Cape list have changed, and are therefore variable 

 as well as Eta. Mr. Abbott speaks of change, but gives no par- 

 ticulars. Lieutenant Herschel also remarked it, but has not 

 given particulars. Mr. Tebbutt, whose accurate observations since 



