244 CARNEGIE INSTITUTION OF WASHINGTON. 



nomena of Cepheid variations. Among other results it is found that in 

 the broadening of spectral lines for a Cepheid variable, rotation may 

 easily play a larger part than pulsations; also spectrographic resolution, 

 photographic technique, and the inherent width of a spectral Une all 

 contribute to the concealment both of the broadening and the asym- 

 metry which affect the lines of a pulsating star. It is concluded that 

 the observed appearance and behavior of the spectrum of a Cepheid 

 variable is not opposed to the hj^pothesis of pulsations. 



During the year Mrs. Shapley has studied the orbits of various 

 eclipsing binaries. An analysis of the system of Y Leonis, based upon 

 observations by Luizet, indicates that this is one of the few eclipsing 

 stars whose light-curve does not permit a solution on the assumption 

 of darkening at the limb which is as good or better than that resulting 

 from the assumption of uniformly luminous disks. In parallax, abso- 

 lute magnitude, and spectrum of the binary, in the dimensions, mean 

 density, and surface brightness of its two components, and in the vari- 

 ous properties of the orbit, Y Leonis is completely normal. The dis- 

 cussion of TW Andromedae, on the basis of measures by Miss Davis of 

 plates made with the 60-inch reflector by Mr. Shapley, is nearly ready 

 for publication. Both photographic and photovisual magnitude-curves 

 have been derived, which determines the color-index for all phases of 

 the light variation. The computations show that at intervals of 

 4.12 days one star (with 50 times the volume of the sun) totally eclipses 

 its companion, which is nine times as bright but of only one-half the 

 radius. 



One of the subclasses of the faint cluster-type variables in the 

 globular system Messier 5 is distinguished by extremely short periods 

 of light variation (4 to 8 hours) and nearly symmetrical magnitude 

 curves. A number of important points connected with the problem 

 of stellar variation are involved in the detailed study of these variables 

 which now is under way. At the same time, the constancy of the Ught 

 for the supposedly invariable stars of this cluster is under investigation. 

 Special series of photographic and photovisual plates have been 

 measured and reduced by Mr. Shapley, Miss Davis, and Miss Ritchie. 

 It is expected that the research will be completed during the present 

 year. 



On Mr. Shapley's recent photographs of clusters, Miss Ritchie has 

 found 98 new variable stars, as follows : 



N. G. C. 4590 = Messier 68 28 



5024 53 22 



6864 75 13 



6981 72 30 



7492 . . 5 



A series of plates has been secured for a detailed study of the vari- 

 ables in the faint and distant cluster N. G. C. 6981. 



