142 SEE— DYNAMICAL THEORY [April 19, 



cumulate in regions of stability, and there build up the smaller into 

 larger bodies. Thus the individual stars being supplied from such 

 varied sources the cluster will necessarily acquire increasing sym- 

 metry, and orderly arrangement, like those actually observed. 



This natural tendency to order and stability will be greatly aug- 

 mented by mutual compensation among the stars of the cluster. As 

 the stars are both gaining and losing matter incessantly, under the 

 mutual interaction of attractive and repulsive forces, it is evident 

 that those which gain too rapidly, will also begin at once to lose at 

 an abnormal rate, owing to the augmented action of the repulsive 

 forces ; and the dust expelled from them will go directly or indirectly 

 very largely to the other members of the cluster, and thus operate 

 to restore the equilibrium of the whole group. Moreover, if any 

 serious collision occurs, by which one star acquires predominant size, 

 it will at the same time acquire such abnormal energy of radiation, 

 that the balance of power will tend to become gradually restored 

 under the action of the repulsive forces at work. 



From these known causes one would expect a cluster therefore 

 to be a mutually compensating system, producing and building up 

 new bodies in vacant regions, where the conditions are stable, and 

 redistributing undue accumulations of mass by the natural balance 

 established between attractive and repulsive forces, as all the stars 

 gain matter from surrounding space and again expel it after a cer- 

 tain repulsive vigor has been attained. The eventual accumulation 

 of so many stars in a comparatively small space largely operates to 

 retain the dust expelled from them in that region; it thus goes to 

 other members of the group, rather than to the rest of the remote 

 stars of the universe, so that in the course of vast time — millions of 

 ages in Herschel's expressive phrase — the cluster accumulates to 

 such grandeur and order as we see in such noble globular clusters 

 as that in Hercules, 47 Toucani, and Omega Centauri. 



It is worthy of note that this simple theory, based on known and 

 established laws, explains not only the origin and growth of these 

 wonderful masses of stars, under conditions of stability ; but also the 

 nearly perfect equality of the individual stars which has always been 

 so bewildering to astronomers. 



