The motion of the atara 



91 



" ^20 — ^02 + il' - ^)2/o*' 



Considering now such points of the sphere, where v,j = 0, we evidently have 



tg 2a;, = tg 2'f = 0 



h. e. apex, the true vertex and the apparent vertex he, — as seen from such points 

 — in the same direction. Q. E. D. 



The direction of the Hue of symmetry for the ohserved proper motions is 

 graphicaUy represented on plate I, which also allows to determine position of the 

 apparent vertex on the sphere. This position evidently is in good agreement with 

 the theorem given above. 



