ASTRONOMY: G. STROM BERG 
41 
the motions of the stars depend upon their positions relative to the center of 
the galactic system. According to Charlier 3 the position of the center as 
derived from 800 B-type stars is 
/ = 236° b = - 14° Distance = 88 parsecs. 
O. R. Walkey 8 finds from 30736 stars of all types the longitude I = 246°. 
These values of the galactic longitude of the center of the stellar system are 
in fair agreement with the value 258° found for the position of the symmetrical 
plane. We may, therefore, conclude that the variation of average radial 
velocity with direction is due probably to a motion of the stars around the 
center of the galactic system. Moreover, if the stars are moving around the 
center of the stellar system we should expect a minimum orbital velocity near 
the center and a maximum at a certain distance from the center. 5 The mini- 
mum in radial velocity near longitude 268° is in agreement with this 
conclusion. 
In the case of the stars nearest to us, we should expect the axes of prefer- 
ential motion to lie nearly in a straight line, since their distance from us is 
small as compared with their distance from the center. 9 To test this question 
I have made an analysis of the radial velocities of the stars in Group III, 
which contains the nearest stars, combining all stars between galactic lati- 
tudes — 66° and +66°. The axes of maximum radial velocity for the result- 
ing curve have the longitudes 157° and 340°, which thus differ by 183°. The 
longitude of the axis of symmetry is 254°, a value in good agreement with that 
found for the more distant stars. The intersection of the surface with the 
galactic plane is shown in figure 4. 
The conclusion to be drawn from these results is that stream motion is prob- 
ably a local effect caused by a preferential motion of the stars in both direc- 
tions around the center of the stellar system. This might have been expected 
from the fact that the motions of the two 'drifts' have been found to be in 
the galactic plane and at right angles to the direction of the center of the 
galaxy. The deviation of the axes of preferential motion from a straight line 
furnishes strong evidence in support of this conclusion. 
1 Adams, W. S., and Stromberg, G., Mt. Wilson Contr. No. 131, Astro ph. J., Chicago, 45, 
1917, (293-305). 
2 Kapteyn, J. C, Groningen, Pub. Astr. Lab., No. 8. 
3 Turner, H. H., Mon. Not. R. Astr., Soc. London, 72, 1912, (387-407). 
4 Eddington, A. S., Ibid., 75, 1915, (366-376). 
5 Mt. Wilson Solar Observatory, Annual Report, 1916, (255). 
6 Eddington, A. S., Mon. Not. R. Astr. Soc, London, F. S., 1915, (521-530). 
7 Charlier, C. V. L., Medd. Lunds Obs., Upsala, Ser. 2, No. 14, 1916, (31). 
8 Walkey, O. R., Ibid., 74, 1914, (649-655). 
9 Stromgren, E., Astr. Nachr., Kiel, 203, 1916, (17-24). 
