MOUNT WILSON OBSERVATORY. 249 



(3) Two eighth-magnitude stars, Lalande 23995 and Lalande 27274, 

 have been found to have radial velocities of +144 and +159 km. 

 respectively. 



(4) Preliminary reductions indicate a double amplitude of variation 

 of about 60 km. in the radial velocity of the variable star X Cygni. 



(5) Photographs secured with a small spectrograph at the primary 

 focus of the 60-inch reflector indicate that the Harvard Variable 3435, 

 with a period of 3^ 52°^, is a spectroscopic binary with a relatively 

 small amplitude of variation in velocity. Similar photographs of the 

 spectrum of T Tauri show no variation from that obtained 3.5 years 

 previously, and that the radial velocity is apparently constant. 



(6) A further investigation has been made of the more refrangible 

 region of the continuous spectrum of stars. About 900 spectrograms 

 have been used and the results confirm the conclusion that for a given 

 spectral t5T)e the violet portion of the spectrum is stronger in the 

 intrinsically faint stars than in the highly luminous stars. The dif- 

 ference is more pronounced in the more advanced spectral types. 

 The extensive material has made possible the elimination and correc- 

 tion of some of the factors which previously have led to uncertainty. 



(7) An investigation of the radial velocities and spectral charac- 

 teristics of stars of type Md has been commenced with the 60-inch 

 and 100-inch reflectors. At present 14 stars have been observed, for 

 12 of which no observations wdth slit spectrographs had been made 

 previously. 



(8) Experiments have been made with the 10-inch refractor and 

 an objective prism to test the possibilities of this instrument for ob- 

 serving stellar spectra in the red and infra-red. A number of photo- 

 graphs of M-type stars show the strong titanium-oxide bands in the 

 red plainly, and the atmospheric line A has been recorded in the spectra 

 of some other stars. The steep color curve of the lens, however, 

 permits only a very short section of spectrum to be photographed in 

 good focus at one time. Accordingly, a problem to which the instru- 

 ment is much better adapted is now being undertaken. This is the 

 observation of the Ha line in the spectra of stars of type B. It 

 seems probable that in view of the great variation in the character of 

 this line, which passes through all the stages from a prominent absorp- 

 tion to a strong emission hne, a classification of B-type stars based 

 upon its appearance will be of considerable value. Two new stars 

 with Ha bright have already been found in this way. 



Spectroscopy of Nebul-e and Star-Clusters. 



Observations on the spectra of certain nebulae and star-clusters have 

 been made by Mr. Sanford with the small sHt spectrograph at the pri- 

 mary focus of the 60-inch reflector. Among these is a photograph of the 

 spectrum of the Crab Nebula made with an exposure time of 48 hours. 



