(aaa 1) 
X.—On the Spectrum of Nova Persei and the Structure of its Bands, as photo- 
graphed at Glasgow. By L. Becker, Ph.D., Professor of Astronomy in the 
University of Glasgow. (With Three Plates.) 
(MS. received May 2, 1904. Read June 6, 1904. Issued separately September 9, 1904.) 
The spectrum of the new star in Perseus, which Dr ANDERson, of Edinburgh, discovered 
1901 February 21, was photographed at the Glasgow Observatory from 1901 March 
3 till 1903 January. From the early photographs one gains the impression that the 
spectrum consists of a number of bright bands of different lengths, fading towards the 
ends, and overlapping each other, thus producing a series of maxima and minima of 
brightness. Near wave-length 5000 the intensity rapidly falls off towards the less 
refrangible side, and the bands appear detached. The middle of each of the three most 
intense maxima approximately coincide with the hydrogen lmes H,, H,, H;, and on 
two photo-plates, March 18 to 20 and March 25, each of the bands is crossed by a 
sharp Fraunhofer line. On the photo-plates taken after 1901 August 1 the bands are 
all detached; some, including the two bands whose middles approximately coincide 
with the principal nebular lines, have almost the same lengths, and suggest a line 
spectrum in which the lines have been broadened into bands, others are considerably 
longer and have pronounced maxima. 
While it was probable that the three hydrogen lines and the two principal nebular 
lines were represented in the spectrum by bands, it remained to be proved that the 
wave-length of a definite point of the band bore a definite relation to the wave-length 
of the line to which it belonged. As a result of my investigations, founded on micro- 
metric measurements and estimates of intensity, I shall show that the bands which con- 
tain a series of reversals are similar in type, and that the ratio of the distance between 
any two points in a band to that between corresponding points in another band is the 
ratio between the wave-lengths. The spectrum of Nova Aurigz resembled that of 
Nova Persei very closeiy ; its changes followed the same course, and it showed the con- 
siderable broadening of the lines into bands, the structure of which has, however, never 
been investigated. The systematic broadening of the spectral’ lines into bands, which 
for Nova Persei amounted to a 35th of the wave-length in March and April, and a 
100th after August, seems to be a feature of new stars, and ought to be accounted for 
in an explanation of these objects. 
2. The Spectrograph.—The spectrograph of 8 cm. aperture is connected to the 
Breadalbane reflector of 51 cm. aperture and 446 cm. focal length. The equatorial 
mounting of this instrument, probably made by the late Thomas Grubb some fifty years 
TRANS. ROY. SOC. EDIN., VOL. XLI. PART II. (NO. 10). 39 
