The Man and His Work. 373 



easier withal to find teachers who could ask questions out 

 of a book than those who could use apparatus if provided. 

 It was customary, therefore, to learn chemistry by rote ; or, 

 in other words, pupils' heads were crammed with unintel- 

 ligible statements about things with queer names such as 

 manganese or tellurium which they had never seen, and 

 would not know if they were to see them. It occurred to 

 Mr. Youmans that, if visible processes could not be brought 

 before pupils, at any rate the fundamental conceptions of 

 chemistry might be made clear by means of diagrams. He 

 began devising diagrams in different colors, to illustrate the 

 diversity in the atomic weights of the principal elements, 

 and the composition of the more familiar compounds. At 

 length, by uniting his diagrams, he obtained a comprehen- 

 sive chart exhibiting the outlines of the whole scheme of 

 chemical combination according to the binary or dualist 

 theory then in vogue. This chart, when piiblished, 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 doctrine of substitution, which 

 does not lend itself so readily to graphic treatment. 



The success of the chemical chart led to the writing of a 

 text-book of chemistry. This laborious work was completed 

 in 1851, when Mr. Youmans was thirty years old. Prof. 

 Silliman was then regarded as one of our foremost authori- 

 ties in chemistry, 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 Silliman's. It 

 was a text-book of a kind far less common then than now. 

 There was nothing dry about it. The subject Avas presented 

 with beautifid clearness, in a most attractive style. There 

 was a firm grasp of the philosophical principles underlying 

 chemical phenomena, and the meaning and functions of the 

 science were set forth in such a way as to charm the student 

 and make him wish for more. The book had an immediate 

 and signal success ; in after-years it was twice rewritten by 

 the author, to accommodate it to the rapid advances made 

 by the science, and it is still one of our best text-books of 

 chemistry. It has had a sale of about one hundred and 

 fifty thousand copies. 



The publication of this book at once established its 

 author's repiitation as a scientific writer, and in another 

 way it marked an era in his life. The long, distressing 

 period of darkness now came to an end. Sight was so far 



