A HISTORY OF SCIENCE 



be nothing strange if some of them, when subjected to 

 the crucible of the sun, which is seen to vaporize iron, 

 nickel, silicon, should fail to withstand the test. But 

 again, chemistry has by no means exhausted the re- 

 sources of the earth's supply of raw material, and the 

 substance which sends its message from a star may 

 exist undiscovered in the dust we tread or in the air 

 we breathe. In the year 1895 two new terrestrial ele- 

 ments were discovered ; but one of these had for years 

 been known to the astronomer as a solar and suspected 

 as a stellar element, and named helium because of its 

 abundance in the sun. The spectroscope had reached 

 out millions of miles into space and brought back this 

 new element, and it took the chemist a score of years 

 to discover that he had all along had samples of the 

 same substance unrecognized in his sublunary labora- 

 tory. There is hardly a more picturesque fact than 

 that in the entire history of science. 



But the identity in substance of earth and sun and 

 stars was not more clearly shown than the diversity of 

 their existing physical conditions. It was seen that sun 

 and stars, far from being the cool, earthlike, habitable 

 bodies that Herschel thought them (surrounded by 

 glowing clouds, and protected from undue heat by other 

 clouds), are in truth seething caldrons of fiery liquid, or 

 gas made viscid by condensation, with lurid envelopes 

 of belching flames. It was soon made clear, also, par- 

 ticularly by the studies of Rutherfurd and of Secchi, 

 that stars differ among themselves in exact constitution 

 or condition. There are white or Sirian stars, whose 

 spectrum revels in the lines of hydrogen; yellow or 

 solar stars (our sun being the type), showing various 



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