428 ON THE THEOKY OF CHEMICAL CHANGES. [XVI. 



nal species, are called chemical elements. These two processes 

 . continually alternate with each other, and a species produced 

 by the first may yield, by division, species unlike its parents. 

 Prom this succession results double decomposition or equivalent 

 substitution, which always involves a union followed by divis- 

 ion, although under the ordinary conditions the process cannot 

 be arrested at the intermediate stage. 



The prevalence of certain modes of division in related species 

 has given rise to the different hypotheses of copulates and radi- 

 cles, which have been made the ground of systems of classifica- 

 tion ; but these hypotheses are based on the notion of dualism, 

 which has no other foundation than the observed order of gen- 

 eration, and they can have no place in a theory of the science. 

 A body may divide into two or more new species, yet it is evi- 

 dent that these did not pre-exist in it, from the fact that a 

 different division may yield other species whose pre-existence is 

 incompatible with the last; nor can the pre-existence of any 

 species but those which we have called primary be admitted 

 as possible. Apart from these considerations, it is to be re- 

 marked that our science has to do only with phenomena, and 

 no hypothesis as to the noumenon or substance of a species 

 under examination, based upon its phenomena, or those of its 

 derived species, can ever be a subject of science, for it trans- 

 cends all sensible knowledge. 



For these reasons, it is conceived that the notion of pre-exist- 

 ing elements or groups of elements should find no place in the 

 theory of chemistry. Of the relation which subsists between the 

 higher species and those derived from them, we can only assert 

 the possibility, and, under proper conditions, the certainty of 

 producing the one from the other. Ultimate chemical analyses, 

 and the formulas deduced from them, serve to show what 

 changes are possible in any body, or to what new species it 

 may give rise by its changes. 



Chemical union is interpenetration, as Kant has taught, and 

 not juxtaposition, as conceived by the atomistic chemists. 

 "When bodies unite, their bulks, like their specific characters, 

 are lost in that of the new species. Gases and vapors unite in 



