Xxii TABLE OF CONTENTS. 



XIX. 



ON THE OBJECTS AND METHOD OF MINERALOGY (1867). 



Mineralogy in its relations to chemistry and natural history . . . 453 



Mineralogy the natural history of all unorganized matter . . . . 454 



Objects to be attained in a natural classification 454 



Views of Oken and of Stallo 454 



The nature of chemical species defined 455 



Varying condensation and equivalents of solid species .... 455 



Relations of vapors to liquids and solids ...... 456 



Evidences of polymerism in solid species 457 



XX. 



THEORY OF TYPES IN CHEMISTRY (1848-1861). 



Kolbe on oxides of carbon as types in chemistry 459 



Ad. Wurtz's criticism of Kolbe 460 



Importance of the conception of types in chemistry 461 



Views of Williamson and of Gerhardt 462 



Laurent on water as a type 463 



The author's views on the water-type 463 



On anhydrous monobasic acids 464 



The conception of condensed or polymeric types 464 



The nature of sulphur, ozone, and nitrogen 464 



Hydrogen the fundamental type 465 



Note on the theory of nitrification 465 



On the value and significance of rational formulas .... 465 



The hypothesis of radicles and substitution by residues .... 465 



Ad. Wurtz on polyatomic radicles 466 



The genesis of the phosphoric acids explained* 466 



Gerhardt on polybasic and sub-salts 467 



The sulphates considered as derived from polyatomic radicles . . . 467 



Priority of the author to Williamson and to Gerhardt .... 468 



APPENDIX. 



The theory of nitrification 470 



Views as to the double nature of nitrogen gas 470 



Its conversion into ammonia and nitrous acid 470 



The intervention of ozone in the process 471 



Experiments of Schonbein on nitrification 471 



Nickles on the priority of the author 472 



Schaefler on the theory of nitrification 473 



