THE STORY OF NINETEENTH-CENTURY SCIENCE 



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 resources 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. Only last year 

 t\vo new terrestrial elements 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 tho sun. The spec- 

 troscope 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 laboratory. 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 

 metallic vapors; and sundry red stars, with banded 

 spectra indicative of carbon compounds; besides, the 



72 





