212 CARNEGIE INSTITUTION OF WASHINGTON. 



The system of parallaxes which is being formed is in no way intended 

 to be taken too seriously, as it is liable to undergo considerable changes 

 with the accumulation of data, but it is primarily intended to furnish 

 a means for deriving the real motions of the stars as approximately as 

 may be at the present time. 



THE VERTEX OF STELLAR MOTIONS. 



Mr. Raymond prepared for publication an uncompleted paper by 

 Professor Lewis Boss on the vertex of stellar motions. This paper, 

 though practically completed before Professor Boss's death, was never 

 published. It offers a simple approximate solution of this compli- 

 cated problem by a method partly graphical. 



The position of the vertex of preferential motion was found to be 

 170?7,-2?5 in galactic coordinates, or 6^ 15"^2, +7° 0' in equatorial 

 coordinates, in very good agreement with the results obtained by 

 other investigators. The ratio of the three unequal axes of the 

 velocity figure proved to be 2.2 : 1.3 : 1, showing the distinct flattening 

 of the velocity figure in the direction perpendicular to the galactic 

 plane. 



VARIATIONS OF SPECTRAL TYPE IN CEPHEID VARIABLES. 



The work of Dr. Albrecht on variations of spectral type in Cepheid 

 variables has been continued and brought to completion for the stars 

 I Carinse and rj Aquilse. In the definitive results the former of the two 

 stars was found to vary from F8 to G9; the latter from F6 to G6. 

 These results, which are based upon the general spectrum, are ap- 

 parently directly opposed to the recent results of Adams and Joy, who 

 found that the variations of type in Cepheids are confined to the 

 hydrogen spectrum and that the general spectrum does not share in 

 these changes. Accordingly, Dr. Albrecht's data were rediscussed 

 with special reference to their possible explanation by the two follow- 

 ing effects in the general spectrum, also referred to by Adams and Joy : 

 (1) a general slight widening of the spectral lines at minimum, and (2) 

 an increase in the intensity of the so-called "enhanced" lines at 

 maximum. A detailed examination shows that nearly all the shifts 

 in wave-length in these Cepheids are satisfactorily explained by a 

 strengthening or a weakening of the same components of the lines 

 (blends) as in the stellar spectra from the "earlier" to the "later" 

 types, rather than by the widening of the lines at minimum or a 

 strengthening of the enhanced lines at maximum, or both. 



Thus, for the present at least, it seems impossible to harmonize 

 Dr. Albrecht's results and those of Adams and Joy. It should be 

 noted that Dr. Albrecht's results would bring into accord for Cepheids 

 simultaneous changes of visual light, of photographic light, of radial 

 velocity, of type based on the general spectrum, of type based on the 

 hydrogen spectrum, and of color-index both observed photographically 



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