JEAN-BAPTISTE-ANDR!^ DUMAS. 553 



and the formuliB of organic compounds are represented on the dual- 

 istic system. Liebig's conceptions were therefore naturally opposed 

 to those advanced by Dumas, but it is pleasant to know that the con- 

 troversy which arose never disturbed the friendly relations between 

 these two noble men of science, who could ajiproach the same truth 

 from diiFerent sides, and yet have faith that each was working for the 

 same great end. In his commemorative address on Pelouze, Dumas 

 expresses towards Liebig sentiments of affectionate regard, and Liebig 

 dedicates to Dumas, with equal warmth, the German edition of his 

 "Letters on Chemistry." 



By the second investigation, as by the first, although Dumas gave a 

 most fruitful conception to chemistry, he only took the first step in de- 

 veloping it. His conception of chemical types was very indefinite, and 

 Laurent wrote of it, a few years later : " Dumas's theory is too gen- 

 eral ; by its poetic coloring, it lends itself to false interpretations ; it 

 is a programme of which we await the realization." Laurent himself 

 helped towards this realization, and in his early death left the work to 

 his associate and friend Gerhardt, who pushed it forward with great 

 zeal, classifying chemical compounds according to the four types of 

 hydrochloric acid, water, ammonia, and marsh gas. Hofmann, William- 

 son, Wurtz, and many others, greatly aided in this work by realizing 

 many of the possibilities which these types suggested ; and thus modern 

 Structural Chemistry gradually grew up, in Avhicb the types of Dumas 

 and Gerhardt have been in their turn superseded by the larger views 

 which the doctrine of quautivalence has opened out to the scientific 

 imagination. It is a singular fact, however, that, while the growth 

 began in France, the harvest has been chiefly reaped by Germans ; and 

 that, although in its inception the movement was strongly opposed in 

 Germany, its legitimate conclusions are now repudiated by the most 

 influential school of French chemists. 



The third great investigation of Dumas was his revision of the 

 atomic weiiihts of manv of the chemical elements, and in none of his 

 work did he show greater experimental skill. His determination of 

 the atomic weight of oxygen by the synthesis of water, and of that of 

 carbon by the synthesis of carbonic dioxide, are models of quantita- 

 tive experimental work. To this investigation, as to all his other 

 work, Dumas was directed by his vivid scientific imagination. In his 

 teaching, from the first, he had aimed to exhibit the relations of the 

 elementary substances by classing them in groups of allied bodies ; 

 and at the meeting of the British Association in 1851 he had de- 

 lighted the chemical section by the eloquence and force with which 



