GEOLOGY. 315 



Sources of High Nebular Velocities. 



In respect to velocities, the Herschellian hypothesis has the tactical 

 advantage of a free field, since nothing is known, independently, of 

 the normal velocities of "island universes," except perhaps in the puta- 

 tive case of the Magellanic clouds that play a part in both hypotheses. 

 On the assumption that the clouds and the galaxy have recently been 

 at their peri-galactic point, both should have acquired in their previous 

 approach velocities much higher than is normal to their class, as well as 

 higher than they will come to have later as their present mutual back- 

 ward pull continues its effects. By assigning a high value to the latter, 

 interpretation might possibly reverse the apparent support this case 

 lends to high velocity as a prevaihng quaUty of great star systems. 

 The following considerations are thought to bear on nebular velocities : 



A. The law of partition of energy among bodies mo\4ng diversely 

 among one another assigns the higher order of velocities to the less 

 massive bodies. If this could be apphed without qualification, it 

 would seem to offer a presumption against assigning the highest order 

 of velocities known in the heavens to the most massive organizations; 

 but the application of the law in this case perhaps does not hold, for 

 lack of a proper basis of reference from which to measure velocities. 

 Velocities, as now measured, would take on enhanced values if referred 

 to a standard representing the motion of galactic systems. 



B. If the spiral, planetary, and other definite nebulse consist of highly 

 dispersed matter deployed from stars or other aggregates, by coUision, 

 disruptive approach, or any analogous agency, a special enhancement 

 of velocity in the nebular product above that of the parent body seems 

 requisite to meet the new disclosures of high nebular velocity. This 

 constitutes an imperative problem. The main studies of the year 

 in cosmogonic lines have been given to this problem in the form of 

 an inquiry into possible sources of such enhancement. The study, 

 however, runs back for several years. The mode of inquiry was chiefly 

 graphic, but the following simple statement may suggest its essence : 



Giant nebulse are naturally attributed to the dispersion of giant 

 stars. The agency of their deployment is assigned to the powerful 

 interaction of their great masses as they pass very near one another at 

 very high velocities. These high velocities are chiefly assigned to 

 mutual attraction under the conditions previously sketched. The stars 

 may not be more than a few radii apart when they pass one another at 

 periastron. The velocities acquired in such very close approaches of 

 very massive stars would, in the higher order of cases, considerably 

 exceed the highest velocity as yet determined for any nebula. The 

 vital issue, however, lies in the conditions that control the motions of 

 the two masses after their closest approach is passed, for mutual attrac- 

 tions are then reversed. If the stars, after passing one another, remain 



