302 DISCUSSIONS IN COSMOLOGY. 



expand the mass against gravity so as to occupy the 

 entire space included within the orbit of Neptune. 

 To this objection it might be replied, that if the tem- 

 perature in question were not sufficient to produce the 

 required expansion, it might readily have been so if 

 the two bodies before encounter be assumed to possess 

 a higher velocity, which of course might have been the 

 case. But without making any such assumption, the 

 necessary expansion of the mass can be accounted for 

 on very simple principles. It follows in fact from the 

 theory, that the expansion of the gaseous mass must 

 have been far greater than could have resulted simply 

 from the temperature produced by the concussion. 

 This will be obvious by considering what must take 

 place immediately after the encounter of the two bodies, 

 and before the mass has had sufficient time to pass 

 completely into the gaseous condition. The two bodies 

 coming into collision with such enormous velocities 

 would not rebound like two elastic balls, neither would 

 they instantly be converted into vapour by the encounter. 

 The first effect of the blow would be to shiver them 

 into fragments, small indeed as compared with the 

 size of the bodies themselves, but still into what might 

 be called in ordinary language immense blocks. Be- 

 fore the motion of the two bodies could be stopped, 

 they would undoubtedly interpenetrate each other; 

 and this, of course, would break them up into frag- 

 ments. But this would only be the work of a few 

 minutes. Here, then, we should have all the energy 

 of the lost motion existing in these blocks as heat 

 (molecular motion), while they were still in the solid 

 state ; for as yet they would not have had sufficient 

 time to assume the gaseous condition. It is obvious, 

 however, that the greater part of the heat would exist 

 on the surface of the blocks (the place receiving the 



