204 CARNEGIE INSTITUTION OF WASHINGTON. 



curve as derived from the absorption lines follows the light curve, the maxi- 

 mum velocity of recession coinciding with maximum of hght. The velocity 

 curve from the bright lines, on the other hand, shows a maximum of velocity 

 at minimum light, so that at this phase there is approximate agreement 

 between the velocities derived from the dark and the bright lines. 



The asymmetry in the spectrum which was noted in previous years has 

 been investigated by rotating the spectrograph so that the slit would lie 

 at several different position angles. The results indicate that the origin of 

 the peculiar spectrum of broad bright hydrogen and helium lines, with a 

 marked displacement toward the red, is situated at a position angle of about 

 135° and a distance of 0''3 from the source of the normal Me-type spectrum. 

 This result is of especial interest in connection with van Maanen's peculiar 

 value for the parallax of this star. 



An examination of the measurements of the sharp bright lines which 

 appear as the star decreases in brightness makes it clear that essentially all of 

 them may be identified with low-temperature lines known in laboratory 

 sources, nearly all of the prominent iron lines of this type being represented. 

 The change from absorption to emission in the case of these hnes as the star 

 grows fainter appears to be accompanied by a reduction of temperature in the 

 star's atmosphere which increases their relative prominence. 



Spectral Classification of the Faint Stars in the Selected Areas. 



This work has been continued by Humason with the slitless spectrograph 

 on the 60-inch reflector. The average exposure time for each photograph is 

 four hours. Seventeen areas have been observed during the year, making a 

 total of 24 which have now been completed. The average number of stars 

 classified in each area is 16, most of them with magnitudes between 11 and 12 

 on the photographic scale. 



Miscellaneous Investigations. 



A study has been made by Merrill of the general physical characteristics 

 of the spectra of 22 S-type stars. The most important result is the identi- 

 fication of the strong bands in the red portion of the spectrum with those 

 due to zirconium oxide. 



Spectrograms of R Coronse were obtained by Joy and Humason near the 

 minimum of light, which occurred in May. A number of bright enhanced 

 lines, many of them due to titanium, appeared at this phase, but soon dis- 

 appeared as the star's brightness began to increase. The general type of the 

 spectrum did not show any very marked change. 



Observations of the two eclipsing variables RS Canum Venaticorum and RT 

 Lacertse at primary minimum of hght show nearly the same spectral type, KO 

 for both stars, but indicate that the former is a dwarf and the latter a giant 

 in its spectral characteristics. 



Several stars of type B with bright lines in their spectra have been studied 

 by Merrill and Humason. Some of these show remarkable changes within 

 a very few days. Humason has also obtained slitless spectrograms of several 

 faint variable stars and a number of the older novae. 



INTERFEROMETER MEASUREMENTS OF STELLAR DIAMETERS. 



Nearly all of the stars previously observed have been remeasured by Pease 

 with the 20-foot interferometer on the 100-inch telescope. The values for the 

 brighter stars remain practically unchanged, except in the case of a Orionis, 



