THE HISTORY OF A STAR. 73 



will be produced during a much shorter period of time. In that 

 case the light of the star will not last long. If the onrush of one 

 stream upon another or a more regular swarm is sudden, we shall 

 have a sudden blaze out of light ; if the onrushing stream is 

 short, the light will soon die ; if it continues for some time, and 

 reduces its quantity, the light will die out gradually. Or again, 

 such a source of supply may fail by the complete passage of one 

 stream through the other. In these ways we shall have various 

 bodies in the heavens, suddenly or gradually increasing or de- 

 creasing their light quite irregularly, unlike those other bodies 

 where we get a periodical variation in consequence of the revolu- 

 tion of one round the other. We shall have " new stars " appear- 

 ing from time to time in the heavens, and they do. 



Unfortunately, no photographs of these bodies to which I refer 

 have been taken. Observations have been recorded, however, of 

 their changing light. The changes can be easily explained upon 

 this hypothesis, but, so far as I know, can not be explained upon 

 any other. 



In one case we had a known star (in Corona) suddenly blazing 

 out from the ninth magnitude to the second, and almost as sud- 

 denly going down again. In another star (Nova Cygni) we had 

 an outburst in a region which observation showed to be without 

 a star, although I do not know whether any special observation 

 of that region had been made for the existence of nebula?. Sud- 

 denly in that part of the heavens a third-magnitude star blazed 

 out ; this took a very considerable time to die down, as compared 

 to the first star, in Corona, and ultimately it got down to the tenth 

 magnitude, and now telescopically it appears as a nebula. 



As in condensing these swarms get hotter, they will get brighter 

 as their volume decreases, and we shall pass from what we term 

 nebulae to what we term stars. It can not be too strongly insisted 

 upon that chief among the new ideas introduced by the recent 

 work is that a great many stars are not stars like the sun, but 

 simply collections of meteorites, the particles of which may be 

 probably thirty, forty, or fifty miles apart. Such eddies and sys- 

 tems, which are not simple, will vary in brightness. In the case 

 of double nebulae condensing we shall get, as I have already stated, 

 a periodic variation in light ; and here we have a simple explana- 

 tion of the facts observed, and hitherto held to be mysterious, in 

 a large number of variable stars. The " new " stars I have already 

 referred to are also easily accounted for on the hypothesis of me- 

 teoric streams. 



It may be asked, Why, considering the millions of bodies in 

 motion capable by this hypothesis of producing them, are not 

 " new stars " seen more frequently ? The reply is simple : We, as a 

 rule, deal with the clashing of small streams ; the temperature does 



