478 
NATURE 

[Oct. 12,1895 

n ARGUS AND ITS SURROUNDING 
NEBULA, &c* 
IN the last paper I had the honour of bringing before the 
Society, I referred to a correspondence which was then pend- 
ing on the star 7, and the attached nebula, in the constellation 
Argo-Navis. It will be fresh in the minds of many of the 
members of this Society that authorities, previously quoted, have 
confirmed the alterations that have been recorded in this object. 
Mr. E. B. Powell, of Madras, writing to the Royal Astro- 
nomical Society some observations on the binary star a Centauri, 
has a concluding note thus :—‘‘I have to observe that to Mr. 
Abbott must be ascribed the first publication of the fact that 7 
is no longer in the dense portion of the nebula, where it was 
seen by Sir John Herschel.”—( Vide Monthly Notices R.A.S. 
vol. 24, p. 172.) 
It was in March 1865, that I first pointed out the fluctuations 
in this object, through the Melbourne equatorial, to Mr. Ellery at 
the Observatory, when the star 7 was out of the nebula, and the 
altered figure of the dark space was filled with 12th magnitude 
stars, richly coloured as described in Monthly Notices R.A.S., 
vol. 25, p. 192. 
Nothwithstanding this in connection with all other evidence, 
strong opposing influences have been brought to bear against 
the movements which have been observed, although it is well 
known to every astronomer that there is nothing stationary in the 
universe. The distance of such objects as the nebula about 7 
Argus is in all cases so immensely great, their position in the sky 
often unfavourable, and convenient times for observing so far 
apart, that any alteration or physical changes may for centuries 
remain unknown. 
The late Sir William Herschel writes, and is followed by Sir 
John, thus :—‘‘ Gravitation still further condensing and so absorb- 
ing the nebulous matter, each in its immediate neighbourhood 
might ultimately become stars, and the whole nebula finally take 
on the state of a cluster of stars,” &c.—(Vide ‘‘ Outlines of 
Astronomy,” 5th edition, p. 640.) Mr. Proctor considers that an 
increased or decreased distance in space may account for the 
fluctuations. 
The present object was observed and faithfully recorded by 
Sir John Herschel, when stationed at the Cape of Good Hope in 
the year 1837. It is quite impossible to say what, if any, altera- 
tions may have taken place in the nebula before that time; but 
it is ceriain that changes have taken place both in the star and 
in the nebula since 1854, and these fluctuations have been so 
great and unusual as to raise a doubt in the mind of Sir John 
Herschel as to their reality. This opinion, coming from such an 
authority, has influenced: many others, who, notwithstanding all 
evidence, and without a single observation of their own, have 
refused to credit these recorded facts. Some also, who have but 
lately commenced observing, contrary to all scientific rule, 
ignore all previous observations made by others, in order to make 
an opening for their own. 
To decide certain points of difference which are said to exist 
between the drawings made by Sir John Herschel, Lieut. 
Herschel, and myself respectively, referees have been appointed 
by the Council of the R.A.S. The present paper has relation to 
the observations made for, and the reply sent to, the referees, in 
answer to their queries on the points alluded to 
In carefully looking over the drawings taken at Bangalore by 
Lieut. Herschel, with the object 7 Argus, 15° above the horizon, 
and also the reversed copy of Sir J. Herschel’s, and on considera- 
tion of the discussion given with the drawings, I do not think 
that Lieut. Herschel’s observations tend to disprove any one of 
the alterations which I have previously communicated to the 
Society. The present drawing, and the answers given to the 
referees, will, I think, render this clear. 
The present observations have been made with the same in- 
strument as the former ones, the object in the same position— 
approximately ©o° above the horizon. The measures were taken 
with a bar micrometer by Cook and Sons, the bars being care- 
fully traced in pencil on the drawing paper, in such a manner as 
exactly to fill the field of the telescope. All the stars visible 
were dotted down, the distances from 7 of the 6th, 7th, and 8th 
magnitude stars were lettered, measured, and catalogued from a 
scale of equal parts, after which the micrometer pencil lines were 
rubbed out, and the nebula inserted. 
The first question put by the referees relates toa comparison ot 
the positions of the principal stars and smaller groups as shown 
* Read at a meeting of the Royal Society of Tasmania, 9th May, 1871. 

in my two drawings, which are said to have a sufficient general 
agreement with each other, considered as eye drafts, while they 
are irreconcilable with both Sir John’s and Lieut. Herschel’s 
configurations. A simple inspection of my drawing ot 1870 with 
the reversed drawing of Sir John Herschel (A.A., plate 4 in the 
Monthly Notices R.A.S.) will show that the following principal 
stars hold a relative position considered as eye drafts, but not 
with the Cape Monograph as expressed in the letter D.D., 
C.C., (A), (®), B-C., (E.), 522, 558, 640, 337, 383, 415, (vs 
(A), &c., &c. There are many other stars in my copy of 1870 
that are not laid down in plate 4, pricked off from Lieutenant 
Herschel’s drawing. 
The other question of note refers to my “having placed within 
11}¥’ (on the scale of my drawing of 7) five stars of magnitude at 
least equal to 7, that is, the 7th magnitude, while in Sir J. 
Herschel’s monograph only one star of that magnitude (marked 
C.) occurs within that distance ;”’ and continues, “can you give 
any elucidation of the cause of the discrepancy? also if you 
would furnish some instrumental determination of the difference 
of R.A., and P.D., between 7 and other stars of equal magni- 
tudes.” 
In my acknowledgment of this letter to Mr. William Huggins, 
F.R.S., &c., I mentioned that it was not my intention or desire 
to dispute either Sir John’s or Lieutenant Herschel’s configura- 
tions, but to call the attention of the astronomical world to the 
altered features of both the star and the nebula, with a view of 
obtaining a solution of the changes seen in this most remarkable 
object. I further stated that the above question was of a 
physical nature, and could only be answered as such. 
On reference to my former papers, it will be seen that mention 
is made, more than once, of the fact that the increase of stars of 
the same magnitude as 7 renders it difficult to know that star 
from others, but by its position, and a marked difference in 
the /ight. ' 
It is to this cause I have so frequently referred the increase 
of light, which I think is now clearly confirmed by a com- 
parison of Lieutenant Herschel’s description with that of Sir 
John’s. At one of the monthly meetings of the Society, Sir 
John Herschel considered the increase of light in the object, 
as recorded, very strange, and remarked, “when I was at the 
Cape the nebula could not be seen at all with the naked 
eye.” Lieutenant Herschel, when at Bangalore, compared 
the increased light, when the object was only 15° above the 
horizon, to that of Pleiades in Taurus. 
Mr. Le Sueur, in his report on the Melbourne reflector, 
says “the nebula around 7 Argus has changed largely in shape 
since Sir J. Herschel was at the Cape. The star shines with 
the light of burning hydrogen,” and in his opinion ‘‘has con- 
sumed the nebula.” 
At the monthly meeting of the Royal Society of Victoria, held 
on the 13th of March, 1871, Mr. Fairlie McGeorge, who has now 
charge of the reflecting telescope at the Melbourne Observatory, 
read a paper in which he referred to some observations made 
with that instrument on the star 7 Argus, and the nebula ; and 
stated ‘that the object had evidently undergone great changes 
since Mr. Le Sueur made his sketches of it. It was now beyond 
a doubt that enormous physical changes were still taking place.” 
The catalogue accompanying my present drawing, made for the 
referees, and laid on the table, will show that there are now in 
the same field two stars of the 6th, two 63, three 7th, four 73, 
four 8th, and nine of the 8} magnitude, and it is literally crowded 
with others of from the 8} to the 12th magnitude. Those lying 
outside the field and occupying an area of about 14°, have their 
magnitudes attached The small cluster I take to be Sir J. 
Herschel’s 3276, described as ‘‘a fine, bright, rich, not very large 
cluster,” if so it is now a beautiful cluster cf richly-coloured 
stars, quite equal to « Crucis. 
It is almost impossible to define the boundary of the nebula, 
as it appears to be gradually fading away, and is not so distinct 
in outline as formerly. 
The finest nights have always been selected for observing, and 
no delineation of the object has ever been given, but what was 
an accurate representation ofits appearance through the telescope. 
The following is an extract from a letter addressed by Mr. 
Severn, of Melbourne, to the Astronomer Royal, and printed in 
the Monthly Notices, Royal Astronomical Society, for April, 
1870 :—“‘I may say that I cannot confirm the new position given 
to 7 Argus in respect to the nebula. I have watched it for 
fourteen years, and itis just where it was ; of course much less 
brilliant.” 
A letter dated 21st June in the same year which I received 
