MOUNT WILSON OBSERVATORY. 249 



(7) The very close agreement of the spectrum of such a star as 

 T Pyxidis, which shows repeated maxuna of Ught, with that of Novae 

 makes it clear that most of the hypotheses of the origin of the latter 

 stars need very decided modification. 



(8) A spectrogram of Nova Persei 1901 was secured in October and 

 November with a small spectrograph used at the primary focus of the 

 60-inch reflector. The emission bands appear of about the same inten- 

 sity as on an earlier photograph, and the continuous spectrum is seen 

 faintly. In addition, an emission band shows at X4471, which is fully 

 as strong as that at X4641. At the date of this photograph Nova Per- 

 sei had increased considerably in its light. 



Miscellaneous Investigations. 



(1) The star R Aquarii has been found by Mr. Merrill to contain the 

 bright lines characteristic of gaseous nebulae superposed upon the 

 normal Md type of spectrum, this being the first case, if Novae are 

 excepted, in which a star has shown the nebular lines. They do not 

 appear to vary with the change in the star's light, and at a time near 

 minimum the spectrum resembles closely that of a planetary nebula. 



(2) A very remarkable change was found to have taken place in the 

 spectrum of o Ceti in the interval between December 12, 1919, and 

 January 7, 1920. The star was approaching its minimum of light at 

 this time. The hydrogen lines, which, like the other bright lines in 

 the spectrum, had been narrow and well-defined on the earlier date, 

 suddenly became extremely broad and diffuse and showed a large dis- 

 placement toward longer wave-lengths. This displacement amounted 

 to about 100 km. relative to the narrow bright lines and is probably 

 in the nature of a widening rather than a bodily shift. At the same 

 time with this change in the hydrogen Unes, the helium line at X4472 

 made its appearance, being broad and diffuse and showing an inter- 

 mediate value of the displacement. Both the hydrogen and heUum 

 lines are cut off sharply at the edge of the continuous spectrum, in 

 marked contrast to the naiTow bright hues due to other elements. 



(3) The ninth-magnitude companion of Castor has been found to be 

 a spectroscopic binary of very short period. Both components have a 

 spectrum of type Md, although the characteristic bands are not very- 

 strong, and appear to be of nearly equal brightness. This star, 

 together with two others, WB 10*^234 and WB 16'^906, are dwarf stars 

 of the Md type. The star WB 10^234 has bright H and K lines, and 

 in all three spectra H^ is the brightest of the hydrogen lines shown on 

 the spectrogTams. 



(4) The long-period Algol variable TT Ophiuchi has a specti-um com- 

 posed mainly of enhanced lines like a Cygni, but with bright hydrogen 

 lines which disappear at certain phases of the star's light. Other stars 

 with one or more bright hydrogen lines are 7.1917 Serpentis and RZ 

 Ophiuchi. 



