ASTRONOMY: C. D. PERRINE 
289 
ON SOME RELATIONS BETWEEN THE PROPER MOTIONS. 
RADIAL VELOCITIES, AND MAGNITUDES OF STARS 
OF CLASSES B AND A. 
By C. D. Perrine 
OBSERVATORIO NACIONAL ARGENTINO. CORDOBA 
Received by the Academy. November I, 1915 
Attention was called in a former paper^ to a decrease of proper mo- 
tion with decreasing brightness in the class B stars, whereas the radial 
velocities showed an increase. Such a condition was found also in the 
class A stars, but more pronounced. Owing to lack of proper-motion 
data for the other classes the matter was not pursued. Since those 
results were obtained I have seen Kapteyn and Adams' investigation^ 
in which they find that the radial velocities increase with increasing 
proper motion for the spectral classes F, G, K and M. The inference 
from the magnitude-results for classes B and A had been that the con- 
trary was probably true for these two classes. It seemed that in general 
large radial velocities would be associated with large proper motions, and 
vice versa. 
After seeing Kapte3ai and Adams' results I classified the B-B5 and A 
stars according to proper motion and found that in fact their velocities 
do appear to decrease sKghtly with increase of proper motion. As 
stated, the contrary was found by Kapteyn and Adams for the classes 
F, G, K and M. The B8-B9 stars were classified separately. These 
45 stars appear to follow the later types with respect to proper-motion 
velocity characteristics if we use the Vi values, or the earlier B and A 
types if we use V. It is perhaps significant that the B8-B9 stars have 
been found not to have a large K term. 
The relations of proper motion and radial velocity for classes B-B5, 
B8-B9 and A are given in Tables I and 11. Table III contains the 
proper motions arranged according to visual magnitude. 
Table I reveals an apparent relation of some kind between the mag- 
nitudes and proper motions of these three classes. The faintest stars 
are found near (but not in) the stars of very smallest proper motions 
in all. In both directions from these the magnitudes decrease numeri- 
cally (stars become brighter). The differences, however, are small and 
so far as the first group is concerned, particularly in class A, may be 
accidental, although examination indicates considerable consistency. 
The Vi of class B-B5 and V of classes B8-B9 and A show a similar 
effect for the radial velocities — the largest being near (but not in) the 
very smallest proper motions. Very noticeable is the sudden increase 
