Vol,. 8, 1922 
ASTRONOMY: G. STROM BERG 
145 
soidal distribution ; the longest and the intermediate axes in all cases lying 
very nearly in the galactic plane and coinciding approximately with the 
% and y axes. The shortest axis is perpendicular to the galactic plane. 
The elongation of the ellipsoids is largest for the bright F stars and decreases 
for later types, the distribution being nearly spherical for the M stars. 
2. The most frequent velocity does not coincide with the origin but lies 
in all cases in the first quadrant of the xy plane, and has the approximate 
values = + 5.6; y — -\- 2.3; z = -\- 1.6 km. /sec. Referring the sun's 
motion to this origin we find its velocity to be 13.8 km. /sec. towards the 
apex Ao = 267°; Do = + 32°. 
3. If we exclude the very brightest F stars, many of which are Cepheid 
variables and stars of similar spectra, and take together stars of types Ay to 
Fg of absolute magnitude 0 to 6, we find that these stars divide themselves 
into two streams. One of these coincides with the general group of giant 
stars, as can be seen from the agreement of its condensation-points with 
that of the giant stars of other spectral types while the other stream moves 
nearly parallel to the Taurus Group. This group*^ is moving towards the 
point q: = 92°; 5 = 4-7° with a velocity of 44 km. /sec. or in galactic 
coordinates with our adopted origin % = — 26, y = +15, 2; = + 4 km./ 
sec. This stream comprises the majority of the stars of F type and its 
existence seems to indicate that a large number of these stars in all regions 
of the sky are traveling with a velocity nearly identical with that of the 
Taurus Group. Even among the brightest F stars as well as the G-type 
giants the presence of members of this group is indicated by the protruding 
form of the equifrequential surfaces in this region. This stream might be 
identified with Kapteyn's First Drift although the galactic latitude is not 
zero. 
4. The dwarf stars among which have been included those with absolute 
magnitudes fainter than 3.0 seem to form a group of their own as regards 
their motions. The distribution of the velocities is ellipsoidal, the major, 
intermediate and shortest axes having the galactic longitudes 162°, 70° 
and 291° and latitudes + 8°, + 9° and + 77°, respectively. The most 
frequent velocity is^i;"— 19; y = — 2; z = 1 km. /sec. which 
nearly coincides with Kapteyn's First Drift, while his Second Drift has 
been swallowed up by the ellipsoidal stream of giant stars. 
There is a very marked asymmetr}^ in the distribution of the velocities 
around the most frequent velocity- vector. The stars of high velocity show 
a tendency to avoid the first quadrant of the xy plane. This asymmetry 
produces a systematic difference between the most frequent velocity and 
the mean of the velocity-components (the centroid). If we omit the stars 
of most rapid motion the centroid falls very near the origin and gives us 
nearly the standard solar velocity. That this asymmetry is not due to the 
selection of stars of large proper motion moving opposite to the sun is 
