414 THE BEAUTIES OF NATURE —__ cuap, 
: proximately measurable. The first star to 
which this test was applied with success was 
that known as 61 Cygni, which is thus shown 
to be no less than 40 billions of miles away 
from us — many thousand times as far as we 
are from the Sun. The nearest of the Stars, 
so far as we yet know, is a Centauri, the dis- 
tance of which is about 25 billions of miles. 
The Pleiades are considered to be at a dis- 
tance of nearly 1500 billions of miles. 
= Ae regards the chemical composition of the 
Stars, it is; moreover, obvious that the power- 
ful engine of investigation afforded us by the 
spectroscope is by no means confined to the 
substances which form part of our system. 
The incandescent body can thus be examined, 
no matter how great its distance, so long only 
as the light is strong enough. That this 
method was theoretically applicable to the 
light of the Stars is mdeed obvious, but the 
practical difficulties are very great. Sirius, 
the brightest of all, is, in round numbers, a 
hundred millions of millions of miles from us ; 
and, though as bright as fifty of our suns, his 
light when it reaches us, after a journey of 
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