﻿96 M. Dumas' s Remarks on Affinity. 



by closely connecting chemical combinations with the purely phy- 

 sical phenomenon of the formation of vapour. 



(5) Finally, that the doctrines with the aid of which it has been 

 attempted to explain chemical phenomena by a distinct unknown 

 cause, or by electricity, have yielded no fruit ; while those which 

 tend to bring it under the laws of universal attraction consoli- 

 date themselves, approach more and more to the facts, and indi- 

 cate better and better the path of progress. 



It would then be natural, just, and useful that Newton's 

 name, and the definitions he gives, both of molecular attraction 

 and of chemical atoms, should be retained in works intended for 

 instruction in chemistry. In my opinion (but I give it with all 

 the reserve which such subjects demand), heat is the real measure 

 of chemical energy, while light and electricity may for the pre- 

 sent be regarded by the chemist either as agents of which he 

 makes use, or as phenomena whose appearance he ascertains. 



Matter and heat would still be, as in Lavoisier's time, the de- 

 finition of the two objects to which the thoughts of chemists 

 should especially be directed. 



The time will doubtless come when, the laws which molecular 

 attraction obeys being themselves known, we shall be able to 

 predict or explain the formation of compounds, their destruc- 

 tion, the preferences and the choice of elements in the formation 

 of combinations, the special affections which acids or bases exhibit 

 in the production of salts ; but before attacking this last and 

 difficult problem, we must know otherwise than by suppositions 

 the bond which connects the shape of the crystals of one chemical 

 species with the arrangement of the atoms the grouping of which 

 constitutes the molecules which are the materials of these 

 crystals. 



I hope the Academy will pardon my having so long occupied 

 it with these historical considerations, and that it will understand 

 the interests attached to them. 



My object would be attained if, on the one hand, I had con- 

 tributed still more vividly to direct the attention of chemists to the 

 relations which connect the motions of heat with the transfor- 

 mations of matter, and if, on the other, I had shown that the 

 principle of the French nomenclature is not unsuited to the 

 classing and naming the compounds of organic or molecular 

 chemistry. 



Lavoisier, in proposing the new nomenclature, stated that the 

 Commission, of which he was the eloquent organ, " had been un- 

 willing to devote itself to great discussions on the constituent 

 principles of bodies and on their elementary molecules — that it 

 had severed itself from the systematizing chemists, who are always 

 ready to accompany facts by an apparatus of reasoning in which 



