244 CARNEGIE INSTITUTION OF WASHINGTON. 



(38) As the average differences of proper motion for the groups 

 observed in each case are closely the same, the observed effect for 

 these stars must be due mainly to differences in physical condition. 



(39) The hydrogen lines are abnormally strong in certain small 

 proper-motion stars. This is due mainly, if not wholly, to the physical 

 condition of these stars, and not to hydrogen gas in space. 



(40) Certain other spectrum lines are weak in the large proper- 

 motion stars and strong in the small proper-motion stars, and conversely. 



(41) The relative intensities of these lines have permitted the abso- 

 lute magnitudes of known-parallax stars to be computed. The method 

 promises to give a satisfactory means of determining a star's parallax 

 from the relative intensities of these lines when its apparent magnitude 

 is known. 



(42) The observed disappearance of the chief nebular lines makes 

 the spectra of Nova Aurigse and Nova Persei identical with those of 

 certain Wolf-Rayet stars, suggesting that the latter may be temporary 

 stars in the later stages of their history. 



(43) Twenty stars in the cluster M 13, in addition to those previ- 

 ously reported, have spectra ranging from Ao to Go. 



(44) Ninety-six per cent of the helium stars brighter than the sixth 

 magnitude in the region galactic longitude 216° to 360°, latitude ±30°^ 

 belong to a single group. 



(45) From the group motion the individual parallaxes of 319 of these 

 stars have been determined. The resulting luminosity curve for the 

 B0-B5 stars is fairly satisfactory. That for the B5-B9 stars is less 

 reliable. 



(46) A special investigation indicates that the method used for the 

 parallax determination of helium stars is applicable to the brighter 

 A-K stars of the first stream. 



(47) A method for the derivation of the mean parallax of a group 

 of faint stars, based upon the luminosity curve and the apparent 

 magnitudes of the group, has been formulated. 



(48) An examination of all available evidence indicates strongly 

 that, on the average, the fainter stars are redder than the brighter 

 ones, and that, apparent magnitude and spectral lines being the same, 

 the stars are redder the farther away they are. 



(49) The relation of these phenomena to spectral distribution, abso- 

 lute luminosity, space absorption, etc., is becoming clearer, but exten- 

 sive investigations will be required to separate the contributing causes. 



(50) 867 chromium and 1,092 vanadium lines have been classified 

 as to their appearance and changes with temperature. 



(51) The enhanced lines of the titanium furnace spectrum are not 

 increased in intensity by the presence of a hydrogen atmosphere; on 

 the contrary, with pressure as great as one atmosphere, the intensities 

 are reduced. 



