688 
DR. W. HUGGINS ON THE PHOTOGRAPHIC SPECTRA OF STARS. 
Addendum. 
(Added March 10, 1880.) 
Since this paper was sent to the Royal Society the following observations have been 
made:— 
Sirius .—A photograph was taken January 2, 1880, which possesses better definition 
than those taken previously. In this photograph a fine line at the position of K is 
seen, of about the same intensity as the line in the spectrum of Vega. The typical 
lines are in a small degree broader and more diffused at the edges than is the case in 
the spectrum of Vega. 
I cannot see with certainty more than ten of the typical lines. I am unable to say 
if the remaining lines 6 and i are really absent or very faint. 
Rigel .—Photograph taken January 3, 1880. All the typical lines are seen. They 
are rather broader than in the spectrum of a Cygni, but not quite so broad as in a 
Virginis. In the arrangement I have adopted in the map, Rigel should be placed 
between these two stars. There is a thin defined line at the position of K. I have a 
suspicion of lines beyond the typical group, and also of a line between a and /3 at X 
3862'5, and a line between ft and y. 
Betelgeux .—Photographs were obtained of this star February 17, 1877, but in a 
photograph taken February 17, 1880, the spectrum is better defined. It is difficult to 
obtain a photograph of this star. An exposure forty times greater than would have been 
necessary for a good spectrum of Sirius gave but a faint spectrum of limited extent of 
Betelgeux. The photographic impression is strongest about G. On the less refran¬ 
gible side it can be traced to F ; on the other side it appears to end abruptly at H, but 
by careful illumination a faint trace of the spectrum can be traced to a short distance 
beyond H. 
Of the visible spectrum of this star, Dr. Miller and myself remark (Phil. Trans. 
1864, p. 425, and Plate 9) : “The light of this star has a decided orange tinge. 
None of the stars we have examined exhibits a more complex or remarkable spectrum. 
Strong groups of lines are visible in the red, the green, and blue portions.” The 
measures are given of about eighty lines. At that time we were not able to see the 
lines of hydrogen at the positions C and F. 
Later (Proceedings of the Royal Society, 1872, p. 388) I remark on this point: “I 
was able with the more powerful instruments at my command to see a narrow defined 
line in the red apparently coincident with Ha, and a similar line at the position of 
H/3. The line Ha falls on the less refrangible side of a small group of strong lines. 
H/3 occurs in the space between two groups of strong lines, where the lines are faint.” 
In the photograph there is a line apparently coincident with Hy (near G) but it is 
