PROCEEDINGS 
OF THE 
NATIONAL ACADEMY OF SCIENCES 
Volumes AUGUST 15. 1917 Number 8 
RELATION OF PREFERENTIAL MOTION AND OF THE SPEC- 
TRAL-CLASS AND MAGNITUDE VELOCITY 
PROGRESSIONS TO PROPER MOTION 
By C D. Perrine 
OBSERVATORIO NACIONAL ARGENTINO. CORDOBA 
Communicated by E. B. Frost. May 28. 1917 
This investigation concerned the relation between the preferential 
motion or streaming of the stars as interpreted by the ellipsoidal theory, 
and the size of proper motion. 
It is based upon the radial velocities of Campbell's L. 0. Catalogs^ 
and Adams' Mt. Wilson Catalog,^ a total of some 1800 stars. The 
stars, after being cleared of the effect of solarmotion, were divided into 
two classes according to size of proper motion, the 'large' ones being 
0. ''10 per year and over, while the 'small' ones are less than O.'^IO, and 
into three classes by magnitude. The stars of Campbell's catalogs were 
divided into two groups, those of magnitude 2.9 and brighter and those 
of 3.0 to the limit of his catalogs which contain few stars fainter than 
5^ magnitude. Adams' stars, with but few exceptions, are between 
magnitudes 5.5 and 6.5, and were treated separately as a third group. 
Following the method of Kapteyn and Adams, ^ the radial velocities, 
without respect to sign, of the stars within 50° of the vertices of the 
ellipsoid were combined to represent the major axis of the elHpsoid 
which is designated by p2. In a similar way those between 60° and 90° 
of the vertices were combined to represent the minor axis Pi. 
The prolateness obtained for the stars of small /x of class F in Camp- 
bell's stars of 3.0 and fainter was 1.91. An examination showed that 
the average value of ji for these stars was considerably higher than for 
the other classes with small /x. The experiment was tried of limiting 
the proper motions of this group to 0.''05 which reduced the prolateness 
to 1.17. None of the other groups were so restricted in the matter of 
491 
