22 On the Theory of Types in Chemistry. 



process as it takes place in nature, dispenses alike with hypo- 

 thetical radicals and residues, both of which are, however, con- 

 venient for the purposes of notation. In the selection of a 

 typical form, to which a great number of species may be referred, 

 hydrogen or water merits the preference from its simplicity, and 

 from the important part which it plays in the generation of 

 species. Water and carbonic anhydride are both so directly 

 concerned in the generation of the bodies in the carbon series, 

 that either may be assumed as the type; but we prefer to 

 regard C 2 O 4 , like the other anhydrides, as ouly a derivative of 

 the type of water, and eventually of the hydrogen type. 



These views were first put forward by myself in 1848, when 

 I expressed the opinion that they were destined to form "the 

 basis of a true natural system of chemical classification ;" and it 

 was only after having opposed them for four years to those of 

 Gerhardt, that this chemist, in June 1852, renounced his views, 

 and without any acknowledgment adopted my own*. Already 

 in 1851, Williamson, in a paper read before the British Associa- 

 tion, had developed the ideas on the water type to which Wurtz 

 refers above ; and to him the English editor of Gmelin's ' Hand- 

 book ' ascribes the theory. The notion of condensed types, and 

 of H 2 as the primal type, was not, so far as 1 am aware, brought 

 forward by either of these, and remained unnoticed until resus- 

 citated by Wurtz in 1855, seven years after I had first announced 

 it, and one year after my reclamation, published in the American 

 Journal of Science, in March 1854. 



My claims have not, however, been overlooked by Dr Wolcott 

 Gibbs. In an essay on the polyacid bases, he remarks that in 

 a previous paper he had attributed the theory of water types to 

 Gerhardt and Williamson, and adds, " In this I find I have not 

 done justice to Mr. T. Sterry Hunt, to whom is exclusively due 

 the credit of having first applied the theory to the so-called 

 oxygen acids and to the anhydrides, and in whose earlier papers 

 may be found the germs of most of the ideas on classification 

 usually attributed to Gerhardt and his disciples f." It will be 

 seen, from what precedes, that I not only applied the theory, as 

 Dr. Gibbs remarks, but, except so far as Laurent's suggestion 

 goes, invented it and published it in all its details some years 

 before it was accepted by a single chemist. 



In conclusion, I have only to ask that future historians will do 

 justice to the memory of Auguste Laurent, and will ascribe to 

 whom it is due the credit of having given to the science a theory 

 which has exercised such an important influence on modern che- 



* Ann. de Chim. et de Phys. [3] vol. xxxvii. p. 285. 



t Proceedings of the American Association, Baltimore, May 1858, p. 19/. 



