44 THE WONDERFUL CENTURY. CHAP. vi. 



sisted in showing that, when the light from an incandes- 

 cent body passes through the same substance in a state 

 of vapor, much of it is absorbed, and the colored bands 

 become replaced by black lines. The black lines in the 

 solar spectrum are due, on this theory, to the light from 

 the incandescent body of the sun being partially ab- 

 sorbed in passing through the vapors which surround it. 

 This theory led to a careful examination of the spectra 

 of all the known elements, and on comparing them with 

 the solar spectrum it was found that in many cases the 

 colored bands of the elements corresponded exactly in 

 position with certain groups of black lines in the solar 

 spectrum. Thus hydrogen, sodium, iron, magnesium, 

 copper, zinc, calcium, and many other elements have 

 been proved to exist in the sun. Some outstanding 

 solar lines, which did not correspond to any known ter- 

 restrial element, were supposed to indicate an element 

 peculiar to the sun, which was therefore named Helium. 

 Quite recently this element has been discovered in a rare 

 mineral, and its colored spectrum is found to correspond 

 exactly to the dark lines in the solar spectrum on which 

 it was founded, thus adding a final proof of the correct- 

 ness of the theory, and affording a striking example of 

 its value as an instrument of research. 



The immediate effect of the application of the spectro- 

 scope to the stars was very striking. The supposition 

 that they were suns became a certainty, since they gave 

 spectra similar in character and often very closely re- 

 sembling in detail that of our sun. Aldebaran is one 

 of the most sun-like stars, being yellow in color and pos- 

 sessing lines which indicate most of the elements found 

 in the sun. White stars, such as Sirius and Vega, show 



