290 CARNEGIE INSTITUTION OF WASHINGTON. 



1'.5 of the center and then increasing to +1.2 mag. in the densest 

 region, where no small or negative color indices are found. This result 

 may indicate that the redder stars are strongly condensed toward the 

 center, that there exists an absorption pecuUar to the central part of 

 the cluster, or that some photographic phenomenon such as the Eber- 

 hard effect has influenced the results. 



(40) Throughout the observed interval of four magnitudes the color 

 index decreases conspicuously with decreasing photovisual brightness. 

 Of the 400 brightest stars, 70 per cent are redder than a normal solar- 

 type star; of the 400 faintest, 85 per cent are bluer than the normal 

 solar-type star. 



(41) By statistical methods the parallax of the cluster is found to be 

 less than 0': 0001. 



(42) Twentj'-three new variable stars have been discovered in the 

 globular cluster Messier 3, bringing the total to 155. Five new varia- 

 bles have been discovered in Messier 13, making a total of 7. 



(43) The spectroscopic and photometric orbits of the binary star 

 RX Herculis have been computed and the absolute Hnear dimensions 

 of the orbit and component stars derived. The mass is peculiarly low 

 for a B-type star. 



(44) Computations on the system of Algol (j3 Persei) show that 

 previous solutions of the photometric orbit are uncertain because of the 

 lack of definite knowledge relative to the amount of darkening at the 

 edge of stellar disks. 



(45) The observed darkening toward the Hmb of the sun is found to 

 conform satisfactorily with the empirical law assumed to represent 

 this phenomenon in the theorj^ of eclipsing binaries. 



(46) The photographic range of the eclipsing star TW Andromedse 

 considerably exceeds the photovisual, indicating that the faint low- 

 density companion is of a redder spectral type. 



(47) Computations on the photometric orbits of five ecUpsing varia- 

 bles of the second spectral type show that the mean densities are much 

 less than any so far found for the whiter stars. 



(48) A special study of the photographic and photovisual light curves 

 of XX Cygni (period 3.2 hours) indicates that its variation is not 

 materially different from that of typical Cepheids. The existence of 

 various types of maxima for this and similar short-period variable 

 stars is definitely established. 



(49) The interpretation of Cepheid variation as a phenomenon con- 

 nected with motion in a binary orbit is found to be untenable. 



(50) The radial velocities of 500 stars have been pubUshed during 

 the year. 



(51) A discussion of these velocities indicates that among the most 

 distant stars the change of velocity with spectral type is much smaller 

 than for the nearer stars. 



