1. In the »Astron. Nachrichten» N:o 4801 I have remarked 
that the distances of the stars of the spectral type B may be deduced, 
for each individual star, from the value of their apparent magnitude, as 
soon as the value of a certain parameter — À — has been determined 
from the radial velocities of the stars combined with their known pro- 
per motions in right ascension and declination. I propose to carry 
out here this determination. | 
2 Let m be the apparent magnitude of a star and r its di- 
stance from the observer, then we have between r and the relation 
(1) r = RI» 
where AR denotes the distance at which the star in question should have 
an apparent magnitude equal to 0".o. 
The relation (1) may, in theoretical researches, more conveniently 
be written in the form 
(1*) Y = Re?" : 
where 
b = 0.2 ‘log 
o 
10 = 0.460517 
As to the parameter R it is a constant for each star, but varies 
from one star to another according to the temperature and the diame- 
ters of the stars. Let o be the semi-diameter and 7 the temperature 
of a star, then we have 
Tih = ef (T) , 
where /,(T) denotes a certain function of the temperature. Hence E 
is proportional to the diameter of the stars. 
Nova Acta Reg. Soc. Se. Ups. Ser 4, Vol. 4, N. 7. Impr. */e 1916. 1 
