MOUNT WILSON SOLAR OBSERVATORY. 221 



during the past year. Since each photograph of a stellar spectrum pro- 

 vides the means of determining the star's intrinsic brightness in 

 addition to its radial velocity, it has seemed desirable to extend the 

 observations to include such of the brighter stars as may be investi- 

 gated in this way. Accordingly all of the stars catalogued in the 

 Avierican Ephemeris with spectral types between FO and M have 

 been added to the observing list. 



Observations have been continued on the fainter stars with measured 

 trigonometrical parallaxes, and this list is now nearly completed. 

 Numerous stars of large proper motion are being investigated for lumi- 

 nosity and radial velocity and are proving to be objects of exceptional 

 interest from both points of view. In addition, a considerable number 

 of stars of small proper motion with magnitudes fainter than 6.0 has 

 been included in the observing program. In the case of the very faint 

 stars increasing use has been made of the 18 cm. camera. While the 

 radial-velocity determinations obtained from such small-scale photo- 

 graphs are necessarily subject to considerable uncertainty, it has been 

 found possible to secure approximate results for numerous stars which 

 could not be obtained otherwise. For absolute-magnitude estimations 

 these photographs are of great value. 



The number of spectrograms obtained during the year is 1,095, dis- 

 tributed as follows : 



American Ephemeris stars 475 



Large proper-motion and parallax stars 268 



Small proper-motion stars 287 



Miscellaneous 65 



Of the photographs 156 were of stars fainter than the eighth magni- 

 tude on the visual scale. 



Radial Velocities. 



The radial velocities of 147 stars have been determined during the 

 year from the measurement of three or more negatives, and one or more 

 values are available for several hundred others. The inclusion of the 

 brighter stars in the observing list has made it possible to compare 

 many of the results with those obtained at other observatories, and a 

 satisfactory degree of accordance has been found to exist. A few of the 

 more interesting results for individual stars are as follows : 



1. The spectroscopic binary Boss 46 proves to belong to the class 

 having abnormal calcium lines. The hydrogen and helium lines show 

 a velocity variation amounting to 485 km. with a period of 3.52 days. 

 The calcium lines show a very slight variation or none at all. 



2. Several high-velocity stars have been found. Of these the ninth- 

 magnitude star A. G. Ber. 1866 shows a velocity of —190 km. The 

 cluster- type variable SUDraconis has a velocity of —195 km. at 

 maximum Ught. 



3. Six new spectroscopic binaries have been discovered. 



