80 A Century of Science 



and the composition of the more familiar com- 

 pounds. At length, by uniting his diagrams, he 

 obtained a comprehensive chart exhibiting the out- 

 lines of the whole scheme of chemical combination 

 according to the binary or dualist theory then in 

 vogue. This chart, when published, was a great 

 success. It not only facilitated the acquirement 

 of clear ideas, but it was suggestive of new ideas. 

 It proved very popular, and kept the field until the 

 binary theory was overthrown by the modern doc- 

 trine of substitution, which does not lend itself so 

 readily to graphic treatment. 



The success of the chemical chart led to the writ- 

 ing of a textbook of chemistry. This laborious 

 work was completed in 1851, when Mr. Youmans 

 was thirty years old. Professor Silliman was then 

 regarded as one of our foremost authorities in chem- 

 istry, but it was at once remarked of the new book 

 that it showed quite as thorough a mastery of the 

 whole subject of chemical combination as Silli- 

 man's. It was a textbook of a kind far less com- 

 mon then than now. There was nothing dry about 

 it. The subject was presented with beautiful clear- 

 ness, in a most attractive style. There was a firm 

 grasp of the philosophical principles underlying 

 chemical phenomena, and the meaning and func- 

 tions of the science were set forth in such a way 



