270 CARNEGIE INSTITUTION OF WASHINGTON. 



B A F G K M 



Distribution of about 2,100 stars with respect to spectral type (abscissae) and absolute magnitude 

 J (ordinate.3). The points and circles represent individual stars. The B stars are those in the 

 Orion (circles) and the Scorpius-Centaurus (points) regions investigated by Kapteyn. The 

 remainder are stars whose absolute magnitudes have been derived spectroscopically by Adams 

 and his associates. For types A to M the circles indicate Cepheid variables and psoiido 

 Cepheidb. 



paratively few stars of intermediate magnitude in either case; and, 

 finally, the K4 to K9 and M stars show two maxinm completely 

 isolated from each other, the first type at +0.7 and +7.0 and the 

 second at +0.2 and about + 10.5. The separation of the two branches 

 of J the curve of development is shown clearly by these results. 



A graphical representation of the results for the 1,646 stars and for 

 the helium stars whose parallaxes were determined by Professor 

 Kapteyn is given in the accompanying diagram prepared by Mr. 

 Hubble. The absolute magnitudes are plotted against spectral types, 

 the Cepheids and the stars of the Orion group among the helium stars 



