x THE STARRY HEAVENS 415 
sixteen years, is at most one two-thousand- 
millionth part as bright. Nevertheless, as 
long ago as 1815 Fraunhofer recognised the 
fixed lines in the light of four of the Stars ; 
in 1863 Miller and Huggins in our own 
country, and Rutherford in America, suc- 
ceeded in determining the dark lines in the 
spectrum of some of the brighter Stars, thus 
showing that these beautiful and mysterious 
lights contain many of the material substances 
with which we are familiar. In Aldebaran, 
for instance, we may infer the presence of 
hydrogen, sodium, magnesium, iron, calcium, 
tellurium, antimony, bismuth, and mercury. 
As might have been expected, the composition 
of the Stars is not uniform, and it would 
appear that they may be arranged in a few 
well-marked classes, indicating differences of 
temperature, or perhaps of age. 
Thus we can make the Stars teach us their 
own composition with light, which started 
from its source years ago, in many cases long 
before we were born. _ 
Spectrum analysis has also thrown an un- 
expected light on the movements of the Stars. 
