NON-MATHEMATICAL SCIENCES 165 



even these represent but a minute fraction of 

 the number that could easily be prepared in the 

 laboratory or found in nature. Out of this 

 variety of chemical substances men have striven 

 to obtain some simplicity or even unity. The 

 Greek elements, earth, air, water and fire, the 

 alchemists' elementary mercury, salt and sul- 

 phur, were crude efforts in this direction. 



Robert Boyle, one of the great contempora- 

 ries of Newton, was the first to make a satisfac- 

 tory classification of substances. He showed 

 that out of combinations of a small number of 

 elementary substances all of the numerous com- 

 pound substances could be obtained, and this 

 is the basic classification of chemistry to-day, 

 although we see that it possesses no finality now 

 that the elements themselves are being decom- 

 posed. The prophecy of Prout that all sub- 

 stances would ultimately prove to consist of 

 nothing but hydrogen has been nearly fulfilled 

 in the recent discovery that protons and elec- 

 trons constitute the material universe. 



We have learned to analyze, not only the 

 substances within our reach, but the sun and 

 stars, and there spectroscopy shows that, except 

 for a very few lines of the spectrum which are 

 still mysterious, they are composed of the same 



