462 THEORY OF TYPES IN CHEMISTRY. [XX. 



ful conceptions of modern chemistry." (Repertoire de Chinrie 

 Pure, 1860, page 359.) And again, he declares that the idea 

 of regarding both water and ammonia as representatives of the 

 hydrogen-type more or less condensed, to be so simple and so 

 general in its application that it is worthy " to form the basis 

 of a system of chemistry." (Ibid., page 356.) 



We have in this theory two important conceptions : the first 

 is that of hydrogen and water regarded as types to which both 

 mineral and organic compounds may be referred ; and the sec- 

 ond is the notion of condensed and derived types, according to 

 which we not only assume two or three molecules of hydrogen 

 or water as typical forms, but even look on water as the de- 

 rivative of hydrogen, which is itself the primal type. 



As to the history of these ideas, Wurtz remarks that the 

 proposition enunciated by Kolbe, that all organic bodies are 

 derived by substitution from mineral compounds, is not new, 

 but known in the science for about ten years. " Williamson 

 was the first who said that alcohol, ether, and acetic acid were 

 comparable to water, organic waters. Hoffman and myself 

 had already compared the compound ammonias to ammonia 

 itself. .... To Gerhardt belongs the merit of generalizing 

 these ideas, of developing them, and supporting them with his 

 beautiful discovery of anhydrous monobasic acids. Although 

 he did not introduce into the science the idea of types, which 

 belongs to M. Dumas, he gave it a new form, which is ex- 

 pressed and essentially reproduced by the proposition of Kolbe. 

 Gerhardt reduced all organic bodies to four types, hy- 

 drogen, hydrochloric acid, water, and ammonia." (Ibid., page 

 355.) 



The historical inaccuracies of the above quotation are the 

 more surprising, since in March, 1854, I published in the 

 American Journal of Science (XVII. 194) a concise account 

 of the progress of these views. This paper was republished 

 in the Chemical Gazette (1854, page 181), and copies of it 

 were by myself placed in the hands of most of the distin- 

 guished chemists of England, France, and Germany. In this 

 paper I have shown that the germ of the idea of mineral 



