140 
ASTRONOMY: ADAMS AND SHAPLEY 
the magnitude values themselves. The two photographs give the fol- 
lowing values: 
Minimum M = +1.8, Maximum M = +0.7, Variation 1.1 
The two conclusions to be drawn from these results are: First, that 
they agree with results based on other considerations such as proper 
motion in indicating that 5 Cephei is a star of very high intrinsic bright- 
ness; second, the variation in magnitude derived from characteristics 
of the spectrum, 1.1, is in very fair accord with the value 0.8, the star's 
known range of visual magnitude. 
In selecting the lines to be measured for the determination of radial 
velocity from the two photographs the consideration was borne in mind 
that different lines might give different velocities. Accordingly, an ex- 
tended list was made out including: (1) a large number of enhanced 
lines; (2) iron lines which show a wide variety of displacements under 
pressure; (3) special lines such as Ey and X 4227 of calcium. The pho- 
tograph taken near maximum was measured by Mrs. Monk and Adams, 
the result given being the mean for the two observers; the other plate 
was measured by Mrs. Monk alone: 
No. of Lines Radial Velocity 
7 4571 (minimum) 55 -f- 3.8 km/sec 
7 4578 (maximum) 68 — 35 . 2 
The radial velocity for the times of the Mount Wilson photographs 
can be predicted by means of the elements of the velocity variation, 
derived by Moore^ from Lick Observatory spectrograms, using in this 
computation the improved Hght elements by Luizet.^ The results are: 
Minimum, +3.7 km/sec. Maximum, —35.2. 
The exact agreement between the observed and computed velocities 
not only checks the results from the two observatories and indicates 
that the range of velocity variation is the same now as eight years ago, 
but also supports Moore's conclusion that the velocity of the center of 
mass does not undergo the variation assigned it by Belopolsky. 
A comparison of the velocities given by the individual Hnes on these 
photographs shows some interesting features. Of these the most im- 
portant is the behavior of the iron Hnes which in the laboratory show 
small displacements under pressure as compared with those which show 
relatively large shifts. The results for the photograph taken near the 
star's maximum are shown in detail in Table I. The pressure shifts in 
angstrom units per atmosphere, given under A, are taken from unpub- 
lished laboratory results by Gale and Adams. The velocities, v, are in 
kilometers, and are the measured values, not corrected for the earth's 
motion. 
