230 CARNEGIE INSTITUTION OF WASHINGTON. 



the year. Mr. Sanford has now determined the orbits of 11 binaries, 6 of 

 which are dwarf stars of spectral types F9 to K2 with periods between 4 

 and 32 days. With the exception of Boss 2447 with a value of 0.21, all of 

 these orbits show an eccentricity of less than 0.10. 



(4) A number of spectrograms of Capella, obtained by Mr. Sanford with a 

 dispersion of three prisms and a 102-cm. camera, were measured by him to 

 test the accuracy of the period derived by Reese at the Lick Observatory more 

 than 20 years ago. The values obtained show that there can be no error in 

 the period as great as 0.01 day, and, hence, that it is unnecessary, in reducing 

 the interferometer measures of this star, to introduce a correction for period. 



(5) The radial velocities of a few additional stars of the R type of spectrum 

 have been determined by Mr. Sanford, thus bringing the number of such 

 stars with measured velocities to a total of 30. The spectrograms have in all 

 cases been measured at least twice, once by means of the Hartmann spectro- 

 comparator and a standard star of type R, and once by the method of wave- 

 lengths. The results are in good agreement. A few spectrograms have 

 been taken in the red portion of the spectrum of these stars near Ha. 



(6) Mr. Merrill has continued his observations on the long-period variables 

 of type Md. The radial velocities of a total of 112 such stars have been deter- 

 mined by him during the past 3 years. Combined with the values obtained 

 at other observatories, velocities for 130 stars are now available. This material 

 is being used in a study of the individual and possible group-motions of these 

 variables, as well as in a discussion of the relative displacements of the dark 

 and bright lines. 



Spectroscopic Determinations of Luminosity and Parallax. 



Since the publication of the results for 1,646 stars, the application of the 

 spectroscopic method of deriving parallaxes has been continued as a regular 

 part of the work of the department. The parallaxes of about 500 additional 

 stars with spectral types F to M are now available, most of which have been 

 obtained during the past year. These include numerous stars of very large 

 proper motion, visual binaries some of which have dynamical parallaxes 

 derived by Jackson and Furner or by Russell, stars in Boss's Catalogue not 

 observed hitherto, and the stars in the Selected Areas under observation by 

 Mr. Humason for radial velocity. No material changes have been made in 

 the methods of reduction used previously. 



Mr. Stromberg has made use of the fact that the systematic and the acci- 

 dental errors of the parallaxes derived by the spectroscopic method are pro- 

 portional to the size of the parallaxes themselves to determine by means of a 

 comparison with trigonometric parallaxes the systematic corrections to the 

 spectroscopic parallaxes, as well as the absolute corrections to some of 

 the more extensive series of trigonometric parallaxes. The results of his 

 investigation indicate that the system of spectroscopic parallaxes used in the 

 catalogue of 1,646 stars is correct within the limits of error of the quantities 

 involved. The systematic corrections to the series of trigonometric parallaxes 

 determined at the Allegheny, McCormick, Mount Wilson, and Yerkes obser- 

 vatories have been found to agree satisfactorily with those derived by van 

 Maanen and Miss Wolfe. 



Professor Russell has made a brief investigation of the relationship of the 

 masses of stars to the spectral characteristics associated with absolute magni- 



