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various important subjects in Mineralogy. 
It might be objected to the application of the natural-historical 
resemblance as a principle of classification, at least in the mineral 
kingdom, that it does not contain any thing from which we 
might learn whether a particular individual belongs to one or 
another species or genus ; and certain characteristic terms are 
then selected or fixed upon, in the representation of the genus or 
species, by which this purpose could be accomplished. This 
mode of proceeding, however, becomes the means of introducing 
inconsistencies and difficulties of various kinds, traces of which 
we also find in the other departments of Natural History. The 
reason of this is, that two most essentially different subjects have 
been confounded with each other, the original representation , 
and the character of the species or genera. The first of these 
consists of the essential unities of the system, and is produced 
by the application of the idea of species, genus, &c. to nature ; 
the second yields the means of distinguishing these unities, and 
serves to collect the single individuals found in nature within 
the compass of these ideas. If both are improperly joined, and 
employed at the same time, neither of them will be found per- 
fectly to answer the purpose, and we shall be reduced to the 
necessity of considering bodies in unnatural connections. The 
natural-historical resemblance, upon which the original repre- 
sentations of the genera, and the higher unities of classification, 
are grounded, must therefore be confined, as a principle of clas- 
sification, to these higher ideas, and, as such, is perfectly suffi- 
cient ; whereas the determination of individuals requires another 
process, dependent upon different considerations. 
This principle of classification is confined to Natural History, 
but is the same in its three departments. If we intend to clas- 
sify natural productions in another science than this, we must 
first have a peculiar principle belonging to the science in ques- 
tion, although the species remains the same ; for this, determined 
according to natural histor}^ principles, or corresponding to the 
natural-historical determination, is the general object of every 
classification. In a chemical classification of minerals, therefore, 
we must not expect or require that the chemical genera, orders, 
&c. should correspond to the natural-historical ones ; still less 
should we, in order to avoid or remedy the discrepancies which 
may arise, employ both principles, the natural-historical and the 
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