292 PHYSICAL SCIENCE 



most probable explanation supposes that the 

 nebula was pre-existent but non-luminous, and 

 was made visible by the flood of light released 

 by the star. That light was reflected as it 

 spread outwards from the centre in ever-widening 

 spheres, and illuminated the scattered wisps of 

 attenuated matter it encountered on its way 

 through space. Calculating from this assumption, 

 it is obviously possible to deduce the distance 

 of the star, which proves to be such that light 

 would take about three hundred years to reach 

 our eyes. It would follow that the phenomena 

 we studied in the last days of Queen Victoria 

 represented changes that were occurring in the 

 depths of space while Queen Elizabeth occupied 

 the throne of England. 



When examined spectroscopically, the light 

 of all the temporary stars yet investigated shows 

 one remarkable property. Bright lines, displaced 

 towards the red, are accompanied by dark lines 

 of similar origin displaced towards the violet. 

 Doppler's principle would indicate that the source 

 of these double lines was a double star, the bright 

 lines coming from a gaseous system emitting a 

 line spectrum, and the dark lines from a partner 

 star in which absorption was predominant. But 

 the difficulties of such a view seem insuperable. 

 The requisite velocities are of the order of many 

 hundreds of miles a second, and no sign of 

 periodicity or even diminution appears in their 

 values. At one time it was thought that the 

 temporary blaze of light might be due to the 

 shock of collision of two stars meeting in space ; 

 but the doubling of the spectral lines indicates 

 a common constitution unlikely inv^iably to be 



