Gravitational Matter through Infinite Space. 173 



This last-mentioned and greatest velocity is probably that of 

 a torrent o£ gas due to comparatively small particles of melted 

 and evaporating fragments shot out laterally from two great 

 solid or liquid masses colliding with one another, which may 

 be many times greater than the velocity of either before 

 collision ; just as we see in the trajectories of small fragments 

 shot out nearly horizontally when a condemned mass of cast- 

 iron is broken up by a heavy mass of iron falling upon it 

 from a height of perhaps twenty feet in engineering works. 



§ 1(3. Newcomb has given a most interesting speculation 

 regarding the very great velocity of 1830 Grooinbridge, which 

 he concludes as follows: — "If, then, the star in question 

 " belongs to our stellar system, the masses or extent of that 

 " system must be many times greater than telescopic observa- 

 " tion and astronomical research indicate. We may place 

 rt the dilemma in a concise form, as follows : — 



" Either the bodies which compose our universe are vastly 

 " more massive and numerous than telescopic examination 

 " seems to indicate, or 1830 Groombridge is a runaway star, 

 " flying on a boundless course through infinite space with 

 " such momentum that the attraction of all the bodies of the 

 " universe can never stop it. 



k; Which of these is the more probable alternative we 

 " cannot pretend to say. That the star can neither be stopped, 

 " nor bent far from its course until it has passed the extreme 

 " limit to which the telescope has ever penetrated, we may 

 u consider reasonably certain. To do this will require two or 

 " three millions of years. Whether it will then be acted on 

 " by attractive forces of which science has no knowledge, and 

 " thus carried back to where it started, or whether it will 

 " continue straightforward for ever, it is impossible to say. 



u Much the same dilemma may be applied to the past 

 " history of this body. If the velocity of two hundred miles 

 " or more per second with which it is moving exceeds any 

 " that could be produced by the attraction of all the other 

 " bodies in the universe, then it must have been flying for- 

 " ward through space from the beginning, and, having come 

 " from an infinite distance, must be now passing through our 

 " system for the first and only time." 



§ 17. In all these views the chance of passing another star 

 at some small distance such as one or two or three times the 

 sun's radius has been overlooked ; and that this chance is not 

 excessively rare seems proved by the multitude of Novas 

 (collisions and their sequels) known in astronomical history. 

 ►Suppose, for example, 1830 Groombridge, moving at 370 

 kilometres per second, to chase a star of twenty times the 



