152 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1912. 



general attraction, except in the neighborhood of certain points of 

 the spirals which have in turn become centers of disturbances. 



The spirals, essentially irregular in their sections and projections, 

 are neither currents nor trajectories. The axis of each one is a 

 synchronous curve of the places which at any given instant are occu- 

 pied by the products of a prolonged and intermittent eruption. The 

 latter are continually evolved in the same central mass which slowly 

 turns upon itself. The spirals therefore tend to become, with increas- 

 ing distances, normal to the radius. The general motions of the 

 matter in this class of nebulae thus conform to the stellar currents 

 of our own milky way if we adopt the views expressed by Schwarz- 

 schild. 



