130 Very — Stellar Revolidions vnthin the Galaxy, 



movements of approach, produced by the attraction of gravity, 

 and movements away from the attractive centers, probably 

 due in the first instance to explosive agencies ; also that the 

 limits of agglomerative and dispersive movements are condi- 

 tioned by the dimensions of the component bodies taking part 

 in the systematic motion, as follows : {a) Agglomeration is 

 characteristic of matter in the condition of collections or 

 swarms of meteors, condensing into stars. Proof follows from 

 the law of gravitation and the admitted existence of meteors. 

 (J) Dispersal prevails after a certain limiting magnitude of 

 mass has been attained as a result of agglomeration, presum- 

 ably owing to instability under great pressure and high tem- 

 perature, and the increase of explosive or repulsive forces. 

 Proof follows from the structure of stellar clusters, which 

 contain no single star of surpassing magnitude as in the solar 

 system, and from the development of clusters as inferred from 

 the spectra of the stars composing them, the less condensed 

 clusters having more advanced spectra, indicating that the pro- 

 gression of a group of stars is towards more complete separa- 

 tion. 



(3) The following are a few of the consequences of a theory 

 of combined stellar concentration and dispersal : 



{a) Comparative permanence of the potent, controlling, stel- 

 lar streams, which are the loci of galactic agglomeration, is 

 indicated by theory, since the attractive force increases as the 

 mass enlarges, while dispersal sets a limit to the growth of 

 aggregations, but does not obliterate them. Hence the orig- 

 inal centers of condensation survive. In the surrounding 

 regions there is presumably motion controlled from the loci of 

 condensation, and with velocities increasing as the agglomera- 

 tions are approached ; but within the galactic agglomerations 

 relative rest prevails, because in these dense regions opposing 

 motions have been largely destroyed by collisions. 



(b) Hence dispersal of satellite hosts from centers of dis- 

 persal in the galactic belts must produce outlying shells of 

 sparsely distributed stars, and an excessively slow circulation 

 of individual members of the accompanying starry hosts around 

 definite galactic streams, which thus become the axes of a revo- 

 lution remotely resembling that of a vortex ring, somewhat as 

 a basaltic column resembles a crystal — not that there is con- 

 sistent direction or parallelism in the orbits, any more than 

 there is in the crystallization, but, on the contrary, a great 

 variety of positions and paths, conditioned only by general 

 agreement in a tendency to helical motion. 



(c) Although the form of the condensed part of the Galaxy 

 may be either a ring, or some kind of spiral branching from a 



