58 F. W. Very — A Cosmic Cycle. 



resulting double spiral or sigmoid curve of the combined 

 trajectories cannot lie in one plane. Moreover, the two arms 

 will not be entirely symmetrical, but both will lie on that side 

 of an equatorial plane through the origin of motion towards 

 which the direction of proper motion points, and unless the 

 proper motion is directed at right angles to the original equa- 

 torial plane, the two branches will have different curves. 

 Figures of this sort have been found by Holden* from a com- 

 parison of a considerable number of spiral nebulae, and 

 Keeler's crowning work with the Crossley reflector indicates 

 that the number of spiral nebulae is very large. 



Friction during the transformation must largely overcome 

 the original rotation. Any remnant of rotary motion is prob- 

 ably confined to the original nucleus or to nuclei at the tips of 

 the horns. In the absence of original rotation or proper 

 motion, the result of an explosion will be a straight nebulous 

 ray, which may retain a central nucleus and two subordinate 

 ones symmetrically disposed in the tips. Many other varieties 

 will suggest themselves. The stars Asterope (Wolf No. 121), 

 mag. 6-5 ; Wolf No. 129, mag. 7*0, and Wolf No. 182, mag. 

 7*5 in the Pleiades, terminating curved nebulous streamers 

 from Maia, mag. 4*5, may serve as an example. 



The existence of a few u run-away" stars, with velocities 

 much exceeding those which gravitation can produce, suggests 

 that under rare circumstances explosions may occur through a 

 large part of a stellar volume, so that the remnant thrown off 

 is not much retarded by the resistance of outer inert layers. 



*E. S. Holden, " On the Helical Nebulae." Pub. Astr. Soc. of the Pacific, vol. 

 i, p. 25, 1889. 



[To be continued.] 



