1922.] The Ninth Indian Science Congress. LS8.C. 47 
logue. He found that in the region Taurus, there are a num- 
ber of stars whose proper motions seem to converge to a 
same linear speed. In the case of such moving clusters, the 
distances are by an indirect method determined with accuracy 
when the point of convergence found, and a complete know- 
ledge of the positions and luminosities of the individual stars 
can be easily obtained. 
Another remarkable cluster is the Ursa Major group which 
was first investigated by Ludendorff. This seems to a 
highly flattened cluster and includes a number of other stars 
scattered over a great part of the sky. Herzprung has shown 
that the star Sirius belongs to the same association. The 
lateral extent of the cluster is about 50 parsees while the thick- 
ness may be only about 8 parsees. The velocity is 29 Km. per 
second towards R.A. 285° Dec. — 2°. 
Several clusters of a similar character have been detected 
the 61 Cygni group and the B-type stars in Orion. The motions 
and other peculiarities of these groups have been thoroughly 
investigated by Kapteyn, Boss and Eddington. A less impor- 
tant cluster has been recently added by Axel Corlin Streaming 
towards 8. Monocerotis. ~ 
rof. Eddington has drawn attention to the important 
fact that the chance attractions of stars in the neighbourhood 
of these clusters seem to have no effect on the motions of the 
individuals and that the clusters preserve their motion in spite 
of the occasional disturbance from interlopers (non-cluster stars) 
in the region they happen to traverse. It is difficult to avoid 
the conclusion that the stars should be moving under the total 
attraction of the whole mass of stars and not under the sway 
of any particular individual or group. As Miss Clerke has 
said ‘these systems may be described as autonomous demo- 
cracies.”’ ever a 
knowledge of Stellar motions is very useful in giving us 
an estimate of the distances of certain groups of stars which 
show at least partly, the scale in which the stellar system has 
been constructed. The proper motions 
valuable information in this direction. The component of a 
j £ the Solar motion is due 
to what is 
er’s motion through space. 
a group of stars, may, on the assumption 0 
