s THE STARRY HEAVENS 419 
the “fiery Dogstar,’ as it used to be, is 
now, and has been for centuries, a clear 
white. 
The star known as Nova Cygni—the “new 
star in the Constellation of the Swan” — was 
first observed on the 24th November 1876 by 
Dr. Schmidt of Athens, who had examined 
that part of the heavens only four days before, 
and is sure that no such star was visible then. 
At its brightest it was a brilliant star of the 
third magnitude, but this only lasted for a 
few days; in a week it had ceased to be a 
conspicuous object, and in a fortnight became 
invisible without a telescope. Its sudden 
splendour was probably due to a collision be- 
tween two bodies, and was probably little, if 
at all, less than that of the Sun itself. It is 
still a mystery how so great a conflagration 
_ ean have diminished so rapidly. 
But though we speak of some stars as 
specially variable, they are no doubt all un- 
dergoing slow change. There was a time 
when they were not, and one will come when 
they will cease to shine. Each, indeed, has a 
life-history of its own. Some, doubtless, rep- 
