Royal Astronomical Society. 305 



On March 18th and following days, comparisons of the comet 

 with neighbouring stars were made with an annular micrometer at- 

 tached to an achromatic telescope, of which the following are the 

 most important : — 



March 19, 7 h 37 m 14 s sidereal time (mean of three observations), 

 the nucleus was east of ij Eridani 3 m 53 s * 22, and 7' 0" south of it. 



March 20, 7 h 36 m 57 s, 5 sidereal time (mean of four observations), 

 the nucleus was east of ij Eridani 1 l m 16 s, 23, and 1 1' 39" north of it. 



March 23, 7 h 27 m 6 S, 3 sidereal time (mean of three observations), 

 the nucleus was 4 m 17 s, 2 east, and 9' 19" south of f Eridani. 



March 29, 8 h 26 m 59 s- 1 sidereal time (mean of three observations), 

 the nucleus was 12 m S, 28 west, and 15' 41" north of AEridani. 



This paper was accompanied by a map showing the path of the 

 comet amongst the stars, and by drawings of its appearance on suc- 

 cessive nights. 



8 to 14. Papers on the Comet, as seen in the Mauritius, in New 

 South Wales, in New Zealand, off the Island of Timor, at Batavia, 

 and in Texas; including Pen- drawings of its appearance by Mrs. 

 Grant. 



15. Letter from the Rev. W. S. Mackay to Sir John Herschel, 

 dated Calcutta, June 10, 1843. Communicated by Sir John 

 Herschel. 



The comet was first seen at Calcutta on the 5th of March, and 

 continued visible until April 3. Distances from bright stars were 

 observed, from which approximate right ascensions and declinations 

 have been deduced. 



Mr. Mackay observes with respect to the star rj Argus, that " in 

 March last, it had become a star of a first magnitude, fully as 

 bright as Canopus, and in colour and size very much like Arcturus. 

 This has been observed by several other persons to whom I pointed 

 it out. Is the star known as a variable star, or is the change now 

 first observed ? a Crucis looked quite dim beside it." 



With regard to the variability of y Argus Sir John Herschel re- 

 marks as follows : — 



The sudden increase of tj Argus from a star intermediate between 

 the first and second magnitude, to a first-rate first magnitude, 

 which took place between 1837 and 1838, was mentioned by me in 

 a letter to Messrs. Beer and Madler, of which an extract is in No. 354 

 of Schumacher's Astronomische Nachrichten* . It was then far in- 

 ferior to Canopus, but equal to Arcturus, and very nearly, or quite 

 so, to a Centauri. It had diminished materially when I left the Cape 

 in April 1838, but was still a great star of the first magnitude. It 

 would appear to be now making another start forward. If this con- 

 tinue we may have a rival to Sirius, or perhaps to the planets. In 

 1838 its brightness was such as to obliterate many curious and in- 

 teresting details of the great nebula in its immediate proximity, 

 which I had fortunately recorded in its former state. 



I do not quite understand Mr. Mackay's distinction between size 

 and brightness of a fixed star. Canopus is at least double of Arc- 

 [* See also Phil. Mag. S. 3. vol. xii. p. 521, 526.] 

 Phil. Mag. S. 3. Vol. 24. No. 1 59. April 1 844. X 



