DR. W. HUGGINS ON THE PHOTOGRAPHIC SPECTRA OF STARS. 
689 
not strong. The spectrum about H is too faint for any certainty as to the characters 
of the lines H and K, which I believe are present. I give the wave lengths of some of 
the most conspicuous lines between G and H. 
4340 
4145 
4319 
4132 
4298-5 
4099 
4252 
4075 
4226 
4025 
4171 
Aldebaran .—The light of this star is of a pale red. We described the visible 
spectrum with some minuteness (Phil. Trans. 1864, p. 424, Plate 11). This star 
requires a very long exposure. An exposure fifty times greater than would have been 
necessary for Sirius, gives a spectrum extending from about F to H, with a faint trace 
of the more refrangible portion. The part from F to H is strongly photographed and 
well defined. It is crowded with lines. About fifty of the stronger lines could be 
measured without much difficulty, but unfortunately, from clouds coming on, the 
spectrum of Capella, which was taken on the same plate, is too weak to give with 
accuracy a fiducial point from which to take the measures. The less refrangible part 
of the photographed portion of the spectrum (roughly from F to G) is brighter 
(darker in the negative) from fewer lines of absorption. In the other portion (from 
about G to H) the lines are more numerous, and exhibit a different character, being 
broader, more intense, and probably more diffused at the edges. 
Capella .—The spectrum of this star was photographed by Dr. Miller and myself 
in February, 1863. It is a white star, and exhibits a visible spectrum closely 
resembling that of our sun. 
The photographs recently obtained exhibit a spectrum from F to beyond S, which 
so closely resembles the Solar spectrum that a photograph of this star would, at first 
sight, be taken for a solar one. This close general resemblance is even maintained on 
closer scrutiny. The lines G, H, and K are of about the same intensity and breadth 
as in the solar spectrum. Beyond H several of the more distinctive groupings of the 
solar lines are clearly seen in the spectrum of this star. I have not attempted to 
measure the lines in detail, for the task would be as great as the measuring of the 
corresponding parts of the solar spectrum. 
The great interest of this star in connexion with the researches contained in this 
paper is that it appears to be a sun in the same stage as that in which our sun is. 
Whether the order of change from the more simple typical spectrum in which these 
researches show that the stars may be arranged, also indicates some of the successive 
