546 DISSOLUTION. 



must ultimately give rise to circulation of a permanent 

 character." Kow what is here alleged of these minor 

 clusters, cannot be denied of larger clusters; and thus the 

 above-inferred process of concentration, appears certain to 

 bring about an increasingly-frequent integration of masses. 

 We have next to consider the consequences of the accom- 

 panying loss of velocity. The sensible motion which disap- 

 pears cannot be destroyed, but must be transformed into 

 insensible motion. What will be the effect of this insensible 

 motion? Already we have seen that were the Earth ar- 

 rested, dissipation of its substance would result. And if 

 so relatively small a momentum as that acquired by the 

 Earth in falling to the Sun, would be equivalent to a molecu- 

 lar motion sufficient to reduce the Earth to gases of ex- 

 treme rarity ; what must be the molecular motion generated 

 by the mutually-arrested momenta of two stars, that have 

 moved to their common centre of gravity through spaces 

 immeasurably greater? There seems no alternative but to 

 conclude, that it would be great enough* to reduce the 

 matter of the stars to an almost inconceivable tenuity a te- 

 nuity like that which we ascribe to nebular matter. Such 

 being the immediate effect, what would be the ulterior ef- 

 fect? Sir John Herschel, in the passage above quoted, de- 

 scribing the collisions that must arise in a concentrating 

 group of stars, adds that those stars " which remain out- 

 standing after such conflicts must ultimately give rise to cir- 

 culation of a permanent character." The problem, however, 

 is here dealt with purely as a mechanical one : the assump- 

 tion being that the mutually-arrested masses will continue 

 as masses an assumption to which no objection appeared 

 at the time when Sir John Herschel wrote this passage; 

 since the correlation of forces was not then recognized. 

 But obliged as we now are to conclude", that stars moving 

 at the high velocities acquired during concentration, will, 

 by mutual arrest, be dissipated into gases, the problem 

 becomes different; and a different inference seems unavoid- 



