Prof. Xaumann on Mineralo/jical Classification. 37 



to disdain, when, mistaking entirely its actual position as a 

 branch of natural history, and, dazzled by the phantom of a 

 supposed higher independent rank, it does homage to the old 

 oryctognostical prejudice, that assistance is to be derived from 

 external characters alone : as if all the properties had not 

 their foundation in the nature of the minerals ; and as if some 

 of them, like garments, belonged to their exterior, and others 

 to their essential constitution. Neither the variety of names 

 of the sciences, by whose assistance we recognise and deter- 

 mine the properties, nor the greater or less delicacy of the 

 procedure required, nor the distinction whether we must 

 merely scratch, file, split, and break the mineral, or also 

 heat, fuse, and dissolve it, can justify us in having exclusive 

 regard to certain properties, while others of the highest im- 

 portance are neglected. This holds good in the classification of 

 minerals, as well as in the determination of species, and hence 

 we believe that chemical composition must be brought pro- 

 minently forward, as one of the essential guides in every 

 aiTangement. 



We should, however, never forget, that the idea of re- 

 semblance must remain as the fundamental principle of our 

 arrangement, in tvhatever properties we may have to seek 

 for this resemblance. We shall thus avoid the objections 

 with which we must charge those mineral systems where 

 identity of composition is the leading idea, and where the 

 minerals are arranged either according to the series of the 

 electro-positive, or according to the series of the electro- 

 negative elements. How little, in all cases, resemblance is 

 founded on identity of composition, is rendered so distinctly 

 apparent by the allotropy {allotropie) of the elements them- 

 selves, and by the dissimilarity of their isomeric combina- 

 tions, that all proofs of the assertion would be quite su- 

 perfluous. Diamond and coal are in reality two entirely 

 different bodies, notwithstanding the identity of their com- 

 position ; and the same holds good in the case of calcareous 

 spar and arragonite, in that of rutile and Brookite, and with 

 regard to many other examples of allotropie elements, and 

 isomeric combinations. Hence, composition alone by no means 

 produces similarity or dissimilarity, and the final result of 



