THE INTERPRETER I49 



ton had refracted a sunray on a prism, and shown 

 that light is made up of differently coloured rays, 

 Wollaston, using a thin slit to admit the ray, observed 

 that it was crossed by a few dark lines. In 1814, 

 Fraunhofer succeeded, by means of yet finer appara- 

 tus, in detecting nearly six hundred of these lines. 

 He, and following observers, made shrewd guesses as 

 to their meaning, but another forty-five years passed 

 before the riddle was read. The details of its solu- 

 tion are given in popular books on astronomy ; and 

 here it must suffice to say that the lines, which are 

 now counted in their thousands, reveal the secret of 

 the chemical constitution of the sun, and tell us that 

 not only are iron, sodium, and some thirty other ele- 

 ments present in his atmosphere, the spectrum of iron 

 alone numbering above two thousand lines, but that 

 the raw materials of protoplasm, notably its most im- 

 portant constituent, carbon, are present also. ' Kirch- 

 hoff's discovery was followed by Sir William Hug- 

 gins's analysis of the light from stars and nebulae, 

 which proved that the former are made of like 

 materials as the sun, himself a star of no high magni- 

 tude, and that the latter are gaseous, the vagrant 

 comets having a spectrum which is a compound of 

 carbon and hydrogen. The same astronomer also 



1 On the apparent absence of oxygen and nitrogen in the solar 

 atmosphere, see my Pioneers of Evolution, p. 165. 



