174 Prof. J. N. Lockyer. On the [Dec. 13, 



to see D 3 , and gives the following particulars of his observations : 

 " I have examined it [the spectrum of the star] frequently, but, so 

 far, no changes have been seen. The C and F lines are brilliant, 

 narrow, and sharp. H<y in the violet is seen with some difficulty. 

 The green is full of very fine delicate dark lines, seen only under 

 good atmospheric conditions, the 6 group being somewhat more 

 prominent than the others. There is also an appearance of faint 

 bright lines, or perhaps spaces between the fine dark lines just men- 

 tioned, seeming bright by contrast. It is difficult to decide on this 

 point. There are in all eight or ten such places. Somewhat nearer 

 to C than to the estimated position of D is a fairly prominent dark 

 band, or, more probably, group of fine lines. ISTot the slightest trace 

 of bright or dark lines can be seen in the vicinity of D. The con- 

 tinuous spectrum close to the bright hydrogen lines appears some- 

 what darker than it does elsewhere, but this I have considered to be 

 the effect of contrast." 



Professor Keeler has since succeeded in photographing dark lines 

 in the spectrum.* 



Belopolsky states that D 3 did not appear in three photographs of 

 the spectrum taken by him in 1892. f 



It may also be stated that the spectrum of this star has been 

 occasionally shown to students at Kensington since 1886, and the 

 bright lines C and F have always been visible. Four dates are 

 recorded in the note-books, namely, September 18, October 13 and 

 October 24, 1889, and October 21, 1894. The presence of bright D 3 , 

 as well as of C and F, was noted on all these dates, except October 24, 

 1889. 



Dr. Copeland has been good enough to communicate to me an 

 unpublished observation made at Dunecht on September 13, 1885, 

 C was then very bright, F just measurable, while D 3 could not be 

 made out with certainty, This observation was made with the 

 15-in. refractor. 



It appears, therefore, that D 3 , and possibly also the bright lines of 

 hydrogen, may be of variable intensity, but it does not seem possible 

 to lay down any law connecting the changes. 



The Kensington Photographs. 



The first photograph obtained at Kensington was taken on Novem- 

 ber 20, 1888, and since then fifty-three photographs have been 

 secured. The instruments employed were those described in my 

 recent paper on " The Photographic Spectra of some of the Brighter 



' Astronomical Spectroscnpy/ Frost's translation, p. 249. 

 f ' Ast. and Ast. Phys.,' 1893, p. 259. 



