BUNSEN AND KIRCHHOFF 331 



1868 -as coming from the sun's atmosphere, which then 

 alone is giving light. 



In this way the 'protuberances' of the sun were recognised 

 as stupendous outbreaks of glowing hydrogen gas, and it was 

 then found possible to examine them thoroughly by means of 

 the spectroscope even in the absence of an eclipse. Attention 

 was then paid to the spectroscopic decomposition of the 

 light from the fixed stars and nebulae, in which matter 

 Fraunhofer had already made a beginning; it was now pos- 

 sible to perform the same chemical analysis, which had 

 already succeeded in the case of the sun, upon these bodies, 

 which for the most part are many thousand and more light- 

 years distant from us. 



It was shown that the whole visible universe, even to the 

 greatest observable distance, consists of no other materials 

 than those found upon the earth. Matter is everywhere 

 alike in character; the universe is a whole; the enormous 

 intervening spaces between one solar system and another 

 do not involve complete separation; all that is familiar to 

 us on earth concerning matter holds good also to the limits 

 of the universe. 



To these achievements of spectrum analysis further re- 

 sults were soon added, which also concerned the processes 

 taking place in the heavens. Christian Doppler, born in 

 1803, son of a master-mason of Salzburg, and professor of 

 mathematics and physics at various institutions in Austria, 

 finally at the university of Vienna, did not live to learn the 

 results of Bunsen's and Kirchhoff 's work; he died early, at the 

 age of fifty. But he had discovered a fact which could now 

 be made good use of: 'Doppler's principle.' This relates to 

 all propagation of waves, including light, and states what 

 happens when the source of the wave, or the observer, move 

 in the direction of propagation. If the motion is not rapid as 

 compared with the rate of propagation of the waves, all that 

 matters is the change in the distance between the source and 



