MOUNT WILSON OBSERVATORY. 275 



panion of Sirius, secured with the 100-inch telescope, confirms in 

 general the previous results obtained some years ago with the 60- 

 inch reflector. The spectral type is somewhat more advanced than 

 that of Sirius, but can hardly be later than F. The line X4481 appears 

 to be abnormally weak. 



9. A continuation of the study of the spectrum of R Aquarii by 

 Mr. Merrill shows the presence of several nebular lines in addition to 

 Ni, N2, and X4363 superposed upon a spectrum of type Md. The 

 displacement lines of the nebular spectrum seem to be the same 

 (within the lunits of error of measurement), with the exception of 

 X4363, which, relatively to the others, appears to be displaced about 

 2a to the violet. 



10. A study has been made by ]\Ir. JNIerrill of the behavior of the 

 more prominent bright lines of certain Md stars and their relative 

 intensities at different phases of light. The same hues are found to be 

 present after maximum in the spectrum of the long-period variable 

 R Cygni, a star with a very different type of absorption spectrum from 

 that of the Md variables. 



11. Mr. Humason and Mr. Merrill have discovered during the year, 

 on photographs taken with the 10-inch refractor and objective prism, 

 more than 50 stars •with the Ha line bright. This makes a total of 

 about 65 such stars found at Mount Wilson. Several of these stars 

 show spectra of the P Cygni tj^pe, the structure being qualitatively 

 similar to that of Novse. 



Peculiar Class A Stars. 



The stars of class A, noted bj- Miss Cannon as having peculiar spec- 

 tra, in which the silicon lines X4128 and X4131 are strong, have a mean 

 absolute magnitude of about —0.2 and are decidedly brighter than the 

 general run of A stars. Those in whose spectra the strontium line 

 X4078 is strong are of about the same luminosity. 



Classification of Stellar Spectra. 



Suggestions have been prepared by Professor Russell, in collabora- 

 tion with Mr. Adams, Cliairman of the Committee on Spectral Class- 

 ification of the International Astronomical Union, and Messrs. 

 Merrill, Joy, and Hubble for an extension of the present notation for the 

 classification of stellar spectra, which should enable most of the 

 ''peculiarities" at present recognized to be represented in a simple 

 fashion, leaving very few cases out of reckoning. These suggestions 

 will be submitted to the members of the committee for action previous 

 to the next meeting of the Union. 



CORRELATION OF LUMINOSITY WITH SPECTRUxM AND COLOR. 



The evidence bearing on the relations of absolute magnitude to 

 spectral type and color index now available has been examined by 

 Mr. Scares and Mr. Hubble in a search for criteria applicable to the 



