ASTRONOMY: A. VAN MAANEN 
227 
ment of these values with the parallactic motion, prove that we have been 
successful in excluding from this group most of the stars which are connected 
with the nebulosity. As a further test I have constructed the diagrams in 
Fig. 1. The number of stars and the total motion were determined for sec- 
tors of 15°; then to smooth the curves, overlapping means for three successive 
sectors were formed. In order to avoid the influence of the large proper mo- 
tions, stars with )u>0''050 were excluded. The smaller diagram shows the 
results for the number of stars, the larger for the total motion in the different 
directions. If among the background stars we have included a considerable 
number of nebula stars, we should find a preponderance of both numbers and 
motion in the direction oi p = 110°, in which the nebula is moving; the fact 
N 
FIG. 1 
that no such preponderance appears, is another proof that only a few stars of 
the nebula system can have been included among the background stars. 
The same diagram shows that neither the maximum frequency nor the 
maximum motion coincides with the direction of the parallactic motion. To 
investigate whether this fact can be accounted for by stream-motion, I com- 
puted the direction of both streams, adopting as coordinates of the vertices: 
We find for 
Stream I, 
a = 
91°, 
8 = -15° 
Stream II, 
a = 
288°, 
d = -64° 
Stream I, 
P = 
139°, 
X = 13° 
Stream II, 
P = 
191°, 
X = 108° 
