BiCKEETON. — Evidence in favour of Impact. 465 



will remember, however, that a few years ago the peculiarities 

 of Algol were so disclosed by its spectrum as to enable us not 

 merely to prove the existence of the dark body, but actually 

 to measure it, to weigh it, and to estimate its velocity. It 

 has proved itself to be almost exactly the size of our own sun, 

 and its motion has demonstrated that there must be a still 

 more stupendous dark globe around which Algol is revolving. 

 It would not surprise me were Professor Boys to prove the 

 existence of this globe by his micro-radiometer. 



The peculiarities of the motions of Sirius have also shown 

 it to have a dark companion that has not only been weighed, 

 but in powerful telescopes can be actually seen as a feebly 

 luminous body. 



The existence of dead suns having been proved, it remained 

 for Nova Auriga to show us the phenomena of tlie clashing of a 

 pair of such suns. Between the 8th and 10th December, 1891, 

 a star appeared where no trace of a star existed before. No 

 eye saw it for many wrecks, but it continued to record its 

 existence automatically by photography. It showed first a 

 considerable increase of light, then a falling-off, then in 

 February it was seen visually. Soon many of the most 

 powerful telescopes in the world were at work, armed with all 

 the resources of our modern methods, and step by step the 

 amazing character of the phenomenon became apparent. The 

 star was double, it had unprecedented velocities, a third body 

 was detected, it expanded into a nebula, it fluctuated in 

 intensity, &c. 



But first let me gather together the salient features of 

 impact as described in my papers, and then compare these 

 with the phenomena disclosed by the new star. Were two 

 dead suns to attract each other they would increase their 

 velocities and move in curved paths. If they grazed, their 

 velocities would be many hundred miles per second — five 

 hundred was mentioned as a reasonable mean in the papers. 

 The effects of the collision would only tell on the parts meeting 

 each other, and the impact, instead of extending to the wdiole 

 body, would affect only a part. This partial impact would 

 produce aii intensely heated body that would remain between 

 the two escaping suns, and that would have so little mass that 

 its temperature would cause each molecule to travel in an out- 

 ward direction until the mass is converted first into a hollow 

 shell of gas (a planetary nebula), and is then finally dissipated 

 entirely into space. 



The enormous velocity of the molecules in all directions 

 would cause the spectral lines to broaden into bands with ill- 

 defined edges. 



The two impacting suns would be sheared by the impact, 

 would recover their sphericity, and continue to pulsate for 

 30 



