296 Jean-Baptiste-André Dumas. 
organic compounds are represented on the dualistic 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 approach 
the same truth from different sides, and yet have faith that 
each was working for the same great end. In his commemora- 
tive address on Pelouze, Dumas expresses toward Liebig 
sentiments of affectionate regard, and Liebig dedicates to 
Dumas, with equal warmth, the German edition of his “ Letters 
on Chemistry.” 
Williamson, urtz, 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 which the types of Dumas and Gerhardt have been 
in their turn superseded by the larger views which the doctrine 
of quantivalence has opened out to the scientific imagination. 
It is a singular fact, however, that, while the growth began 1D 
France, the harvest has been chiefly reaped by Germans; an 
that, although in its inception the movement was strongly 
opposed in Germany, its legitimate conclusions are now repu~ 
diated by the most influential school of French chemists. 
The third great investigation of Dumas was his revision of 
the atomic weights of many 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 carbone 
dioxide, are models of quantitative experimental work. +° 
substances by classing them in groups of allied bodies; and at 
the meeting of the British Association in 1851 he had delighted 
the chemical section by the eloquence and force with which he 
exhibited such relations, especially triads of elementary SU9° 
stances; such as chlorine, bromine and iodine; oxygen, sulphur 
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