Yery — Stellar Revolutions' within the Galaxy. 131 



center, as suggested by Easton,* the limiting volume which 

 includes the sparsely distributed, but controlled, outlying mem- 

 bers of the host, may be approximately a sphere. A different 

 history, or mode of formation, is indicated for the central forms 

 and their surroundings. 



{d) If velocities occasionally generated exceed the control- 

 ling power of the combined mass, such portions escape. Hence 

 instances of this sort can not accumulate, and must be rare. 



Figure 1 shows the paths of stars thrown off from a central 

 condensation in various directions with velocities insufficient 

 to produce separation from the system. If the direction is 

 such that another branch or condensation has mass enough to 

 draw the return path to one side, the circulation may be 

 around this, rather than around the original member. Owing 

 to the complex form of the Galaxy, perturbations are of a mag- 

 nitude equaling or excelling the attraction of a parent center. 



The revolutions shown are of excessive slowness, and of 

 sufficient duration to allow a majority of the encompassing 

 host to have passed through the stages of development charac- 

 terized by first-type spectra, and to have attained the solar 

 type. 



(4) In order to reach some conception of the dimensions and 

 periods of stellar revolutions around the Galaxy, I propose to 

 take the galactic parallax = -J-q of a second of arc, correspond- 

 ing to a distance I) = 600X10'^ km. in round numbers, as that 

 of the sun from a galactic center of attraction, and to trace 

 some of the consequences. Let Dj be Neptune's distance from 

 the sun. For a constant mass, the parabolic velocity is pro- 

 portional to Vl/D ; hence the parabolic velocity from solar 

 attraction at the sun's assumed galactic distance is 



* Astrophysical Journal, xii, 136, 1900. 



