138 Very — Stellar Revolutions within the Galaxy. 



through this mass, parallel with the sun's motion, will inter- 

 sect a plane through the sun at right angles to the direction of 

 motion and meeting the celestial sphere in a great circle 90° 

 from the apex, in a point whose projection may lie anywhere on 

 this great circle ; but if the motion is actuated by the predom- 

 inating attraction of a part of the galactic stream, the plane of 

 motion is probably nearly perpendicular to the general direc- 

 tion of the Galaxy on either side of the chief attractive center, 

 because the attraction of the adjacent portions of the galactic 

 stream, if at all symmetrical, will bring the ]3lane of motion 

 into approximate coincidence with a radial plane through the 

 rectilinear axis of curvature of the stream. It is also probable 

 that the dominant region of attraction for our sun lies in the 

 Milky Way not far from the apex of the sun's way. 



The projection of a line through the center of attraction, 

 parallel to the sun's path, will be a portion of a great circle 

 through the apex, cutting the Milky Way in Cygnus, and 

 intersecting the trace of the plane through the sun at right 

 angles to the line of motion, somewhere in the constellation 

 Aquarius. The projected line is nearly parallel to the direc- 

 tion of proper motion of our near neighbor, 61 Cygni, which 

 very likely forms one system with the sun. 



The axis of orbital revolution can not be placed at present ; 

 but as our sun approaches perigalacteum, the apex of motion 

 will recede to a point on the celestial sphere 90° from the 

 Milky Way, and the direction of motion of the apex will then 

 determine the axis of the orbit. Long before that time, how- 

 ever, the present constellations will have been entirely broken 

 up, and only the more general shapes of portions of the Milky 

 Way will preserve a kind of fixity. All that can be said at this 

 time is that the sun has advanced toward the Galaxy from its 

 northern side, passing through its plane to its southern side, and 

 that the sun is now within the stellar coil and nearly in the 

 galactic plane. 

 Areturus, Va. 



