208 CARNEGIE INSTITUTION OF WASHINGTON. 



change considerably the location of the apices of motion of some of 

 the stars employed; but for general statistical considerations the data 

 furnish a very fair representation of the distribution of the motions 

 of these stars. Dividing the material according to velocity into two 

 groups of stars, the first consisting of 446 stars whose velocity does not 

 exceed 80 km. per second, and the second including 71 stars of velocity 

 ranging from 80 to 500 km., the apex of solar motion was found to be 

 at right-ascension 270°, declination +28° from a solution of the first 

 group, with a velocity of 21 km. per second for the sun. 



The apex of solar motion derived from the high-velocity group placed 

 the apex at 298° right-ascension and +47° declination, with a solar 

 velocity of 89 km. The high velocity for solar motion as derived from 

 this latter group, and the location of the apex, is ascribed partly to 

 the peculiar distribution of the velocities of the rapidly moving stars. 

 The peculiarity in the motion of these stars was noted in the report of 

 the Department in the Year Book for 1918. The stars are found to be 

 moving approximately in a region of the Galaxy extending from galactic 

 longitude 130° to 340°. The fact that no stars of high velocity are 

 moving toward points opposite this region renders it probable that we 

 are dealing with a physical group and certainly accounts for the high 

 velocity of the solar motion derived from such data. 



It is also very probable that the increase in the declination of the 

 apex of solar motion with decrease in apparent magnitude, found when 

 the stars have been divided according to apparent magnitude, is 

 attributable to the same cause, for in general the stars of fainter magni- 

 tude employed in the investigations are those with high-space veloci- 

 ties. The group of high-velocity stars is not similar to such groups as 

 the Taurus cluster, for it fans out, but the motions of these stars are 

 entirely at variance with general motions and demand further investi- 

 gation to determine the cause of the phenomenon. 



As a matter of interest, partly to test the effect of a change in the 

 value of the parallax upon the computed elements, a space velocity of 

 100 km. per second was assumed for 63 members of the group and the 

 parallax of each star was computed on this basis. It was generally 

 found that the computed parallax differed by a small amount from the 

 observed parallax. This suggests the bare possibility that the space 

 velocities of at least many of these stars may be similar in size. A 

 division of the material into giant and dwarf classifications placed 

 the solar apex at 269° right-ascension, +18° declination for the giant 

 stars, with a solar velocity of 20 kilometers, and at right-ascension 

 275°, declination +36° for the dwarf stars, with a solar velocity of 

 25 kilometers per second. It seems probable from the material treated 

 that the sun's velocity in space is somewhat greater, therefore, than 

 the generally accepted value. The A and B type stars were not used 



