PHILOSOPHICAL SOCIETY OP WASHINGTON. ,. 83 



Although the gravity of Lanthan is 0.833, it became neces- 

 sary to place the Lanthan minerals as an appendix, because La 0, 

 which would be the species, is not known at present, and there- 

 fore their position with reference to the other anhydrous carbo- 

 nates is not quite clear 



It will readily be seen that we obtain by this arrangement 

 groups very similar (natural) both in their chemical composition 

 and their physical characters 



In acknowledging only such as species that simply fill the 

 general formula of some class or subclass, and regarding every 

 mineral of the same chemical character, but with various I'eplaee- 

 meiits of RO, as a subspecies, many minerals heretofore regarded 

 as species will only obtain the rank of subspecies or of varieties. 



Thus, Aragomte, with the same composition as Calcite, but 

 differing in crystalline form, gravity, hardness, etc., can only be 

 regarded as a variety of the species and subspecies Calcite. Gra- 

 plnte, chemically identified with Diamond, although phj^sically 

 differing, will in a strict system receive the place of a variety. 

 MeMcinnabarile, chemically Cinnabarite, differing, however, in 

 structure, gravity, color, etc, can be nothing but a variety of 

 tiie latter mineral. 



In retaining the one name for the species or subspecies, the 

 right of priority will be observed. Metacinnabarite was named 

 in 1872, while " Cinnabarite" has been in use already for a very 

 long time. 



In proposing the above rules for classifying minerals, one of 

 my chief objects is to assume a basis for a more rigorous distinc- 

 tion of the terras species and varieties and those subordinated to 

 them, and although this to a certain extent may seem to be going 

 too far, in partly giving up the characteristic individuality of a 

 mineral, a classification of this kind may claim to be a more 

 logical one than many others, and in a science like mineralogy 

 this may perhaps be one of the chief requisites. 



