226 CHEMISTRY 



for its further development. This combination of intellectual interest 

 with utility gave the science a higher place in educational affairs; and 

 when Liebig opened the first university laboratory for students at 

 Giessen, a new era for chemistry began. Before that time the chemist 

 was either self-taught or trained in private laboratories; now he 

 could aspire to scholastic honors and assume his proper position as a 

 learned man. As a discoverer, Liebig was great, but his chief services 

 to chemistry were in his educational work and in the application of 

 science to agriculture. To those achievements his wide reputation 

 is mainly due. 



For chemistry, then, the second half of the century opened aus- 

 piciously. Chemists were needed for technical purposes and as teach- 

 ers, and resources were placed at their disposal almost without stint. 

 Discovery was stimulated, investigation became more systematic, 

 theory and practice developed side by side. Practical applications 

 followed the most abstract researches; new industries sprang into 

 existence, and in education mere bookishness gave way to experi- 

 mental methods. A great but silent revolution had taken place, whose 

 magnitude will be better appreciated by posterity than by ourselves. 

 Had science done no more than to replace supposition by experiment, 

 and chance discovery by orderly research, the revolution would still 

 have been one of the greatest in the history of mankind. Chemistry 

 was not the sole agent in effecting the transformation, but it surely 

 played one of the leading parts. 



All of the agencies which I have mentioned helped to encourage 

 the study of organic chemistry. It was systematic, and therefore 

 easily taught, and it was full of suggestiveness both for teacher and 

 pupil. Its practical applications were many, and gave the investi- 

 gator hope of material rewards; the revelations of coal-tar alone were 

 enough to stimulate chemists to the greatest activity. So it happened 

 that inorganic chemistry fell into neglect, and the majority of chem- 

 ists followed the leaders into the new field. The conceptions of chem- 

 ical structure, which had been slowly evolving during many years, 

 were given definiteness by the discovery of valence, and of this the 

 benzene theory was perhaps the most brilliant application. Frank- 

 land, Williamson, and Perkin in England; Dumas and Wurtz in 

 France, Kekul6 and Hofmann in Germany, and the Russian Butlerow, 

 are the conspicuous names connected with the modern movement. 

 Organic chemistry became an imposing structure, and yet it rested 

 upon the foundations which the older chemists had laid. The con- 

 stitutional formulae were built upon atomic conceptions, valence 

 itself was a property of the atom, and complete acceptance of the 

 new ideas was impossible until after Cannizzaro had revised the 

 atomic weights and brought them into harmony with Avogadro's 

 law. Up to that point there was a chaos of rival doctrines, after- 



