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ever referred to. Again, certain actions of a particular species with the 

 blow-pipe, flaxes and acids, are enumerated, but they are considered as 

 being properties inherent to the mineral, like the cartilaginous, or bony 

 skeleton of the fishes ; whereas, they ought to be mentioned as an action 

 purely artificial, but pet-formed in order to reveal the composition of the 

 minei-al, the sole property which is really inherent to it. 



But in the books treating of Determinative Mineralogy the defect 

 becomes shocking to everyone who regards mineralogy, not as a 

 mechanic's trade, but as a real science, built on the most beautiful, and 

 ^lid, and comprehensive principles. Principles ! They have ceased to 

 exist. You would think whilst studying descriptive mineralogy that 

 chemistry, though much neglected, was however the basis of classifica- 

 tion. You had seen collected in one group the minerals into which 

 Iron enters as an element, in another group no species appeared but 

 those that contained Calcium ; but you now discover that you have been 

 on the wrong track. All your mineralogical education has to be done 

 over again. Pay no more attention to that chemical composition, or 

 that ci'ystalline foi in to which so much importance was attributed, at 

 least speculatively, in the theoretical and descriptive parts. Now they 

 vanish befoi'e external characters, and will appear again only at the very 

 end, when all other characters will have failed to individualiza the 

 species. Fusibility is brought to the front ; all minerals henceforth are 

 divided into two classes according as they fuse with greater or less diffi- 

 . cnlty, or not at all. Be not surprised now to find together minerals 

 which difier in every possible respect except that of fusibility. Are 

 there two more different minerals than Bismuth and iNIagnetite ] In 

 composition one is the pure, well-known metal, the other the famous 

 oxide of iron ; in crystallization the former belongs to tha rhombohedrai 

 system, the latter when crystallised exhibits the form of the Isometric. 

 All their other properties are likewise at the antipodes of each other. 

 lUsmuth is exactly twice as heavy as Magnetite ; its silver- white tinge 

 cuatrasts strongly with the black colour of the magnetic ore ; you scratch 

 it with the linger nail, but your steel knife cannot affect the other ; the 

 one has a strong afB.nity for oxygen, which it absorbs rapidly under the 

 action of heat, whilst the other, already saturated with oxygen, can only 

 be reduced by the heat applied. I repeat again, can they be more 



