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1922.] The Ninth Indian Science Congress. LS.C. 45 
be a circle. If the Sun also is considered moving, the velocity 
diagrams will change into ovals, the elongation of the oval 
Kapteyn announced in 1905 that the phenomena are satis- 
factorily explained by supposing that the great majority of 
relative to the Solar system make an angle of 100° with each 
other. The speeds are as 1°52 to 0°8 and the numbers of stars 
in the two systems are as 3 to 2. Further the motion of one 
swarm relatively to the other is found to be exactly parallel to 
the plane of the Milky Way. Kapteyn has given the name star- 
streaming or star drift to this tendency of star to move in 
y of 1900 stars 
times the velocity of the Sun, ie. about 48 Km. per second. 
Schwarzchild has developed another method of represent- 
ing these peculiar motions which is called the Ellipsoidal 
hypothesis. In this theory, unlike Kapteyn’s, the stars are 
all considered to belong to one system and if the components 
one direction 
than in any other, these motions may be represented graphi- 
callv by all the radii of an ellipsoid whose longest axis coin: 
readily be seen that the principle underlying the two representa- 
tions is practically the same—@ greate 
both serve as a good first ap- 
me results over the limited period 
of time we can deal with. 
A closer approximation than the two drift theory was 
discovered by Halm who pointed out at a certain number 
of stars form a separate third drift (called by him Drift 0) 
without seeming to participating 11 the two great —— 
of Kapteyn. Their apparent motion 1s directed towards t : 
Solar antapex and thus all stars of this drift would be at os 
in space if the effect of Solar motion were eliminated. e 
