Mineralogy, according to the Principles of Professor MOHS. 311 



The progress of the gradations in the single properties of the 

 individuals within one species, is what may be called with pro- 

 priety a transition or passage ; and individuals in which such 

 a progress is observable, are said to pass into each other. The 

 transitions arise from the series of characters ; and we may infer 

 from the existence of transitions between individuals, that they 

 belong to one and the same species. Transitions exist only 

 within the species, and no transition can take place from one 

 .species into another, because this very occurrence of a transition 

 between two supposed species, would unavoidably join them into 

 a single one. In regard to the numerous incorrect transitions 

 mentioned in mineralogical books, Professor MOHS says, " that, 

 " wherever the transition is correct, the determination of the spe- 

 " cies is erroneous, and vice versa ; that the transition is falsely 

 " stated, if the determination of the species be correct." * 



The species, obtained by the process explained above, is the 

 object, not the product of classification, as some mineralogists 

 seem to believe, who begin and terminate classification with- 

 out previously digesting the idea of species. It has been a 

 common practice to take advantage of the constancy of the che- 

 mical composition within well defined natural-historical species, 

 and thus to exclude, as it were, the definition of the species from 

 the province of natural history, and to resign it entirely to the 

 ascendancy of chemical principles. Yet the inferences drawn 

 from chemical observations presuppose the existence of the spe- 

 cies, as produced by the comparison of the properties observable 

 in their natural state. One specimen of a species having been 

 analysed, we may conclude that other specimens of the same spe- 

 cies consist of the same principles, in the same proportion ; but, 

 we are entitled to draw this conclusion only, because the ana- 



* MOHS' Treatise on Mineralogy, Transl. vol. i. p. 337. 



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