248 CARNEGIE INSTITUTION OF WASHINGTON. 



star T Pjrxidis, which shows a light-curve similar to that of Novae and 

 which reached a maximum of light for the third time in 30 years on 

 April 8, 1920. A brief summary of the observations follows: 



(1) A photograph of the spectrum of Nova Ophiuchi 1919, taken on 

 November 2, 1919,showeda spectrum characterized by numerous bright 

 bands of hydrogen, calcium, and enhanced iron and titanium. Well- 

 defined absorption lines accompanied the bands and were displaced 

 5.0 a toward the violet. These displacements and the widths of 

 the bright bands, as in the case of other Novse, were proportional to 

 wave-length. The radial velocity of the star was found to be +6 km. 



(2) A photograph of NoVa Ophiuchi taken on July 26, 1920, showed 

 that the spectrum had changed to the nebular type, with strong bright 

 bands and a very weak continuous spectrum. 



(3) The spectrum of Nova Lyrse 1919 was photographed on Febru- 

 ary 5. In addition to numerous bright bands superposed on a faint con- 

 tinuous background, double absorption lines of hydrogen appear, and 

 also a number of other lines due probably to oxygen and nitrogen. The 

 displacements of the components of the hydrogen lines are closely in 

 the ratio of 2 to 1, being —27.5 and — 14.3 a, respectively, at Hy. The 

 oxygen and nitrogen lines are displaced by the larger amount. The 

 spectrum of this star is very similar to that of Nova Aquilee 1918, 9 

 days after its maximum of light, and represents what appears to be an 

 intermediate stage in the development of the spectra of Novse. 



(4) Photographs of the spectrum of Nova Aquilse 1918 have shown 

 remarkable changes and distortions in the form of the chief nebular 

 lines belonging to the disk about the star. These appear to be almost 

 certainly due to internal motions and rotation in this disk, a conclusion 

 already reached by the observers at the Lick Observatory. The 

 continuous spectrum of the star is strong and suggests a development 

 toward the Wolf-Rayet type of spectrum. 



(5) Observations of the variable star T Pyxidis made on April 11, 

 27, and 30 show a remarkable degree of similarity between its spec- 

 trum and that of Novse at an intermediate stage. The bright bands of 

 hydrogen are about 25 a wide and are accompanied on the violet 

 side by complex absorption lines. Numerous absorption lines of 

 oxygen and nitrogen are present, together with the helium line at 

 X4471. In the interval between April 11 and April 27 the displace- 

 ment of the absorption lines increased from —22.7 to —28.1 a, a change 

 of much the same order as that found in Nova Aquilse 1918 during its 

 early history. 



(6) The displacements of the successive components of the hydrogen 

 absorption lines appear to show a marked tendency toward a definite 

 integral ratio to one another, the three strongest components having 

 the values —28.1, —21.3, and —14.4 a when reduced to X4600. A 

 faint component with a displacement of — 7.2 a has also been measured. 



