. 239. NOMENCLATURE. 361 



this end, the most desirable are the systems of crystallisa- 

 tion and the relations of cleavage. Examples are, hexahe- 

 dral, prismatic, rhombohedral Iron-pyrites ; rhombohedral, 

 octahedral, dodecahedral, prismatic Corundum ; rhombohe- 

 dral, octahedral, prismatic Iron-ore, and many others. If 

 two or three species of a genus belong to one system of 

 crystallisation, one of them retains the adjective express- 

 ing the system ; the others receive a denomination taken 

 from a general property of crystallisation, or of cleav- 

 age, as in peritomous and pyramidal Titanium-ore, in 

 prismatic, prismatoidal, hemi-prismatic, and paratomous 

 Augite-spar, in rhombohedral and peritomous Ruby -blende, 

 in rhombohedral, macrotypous, brachytypous and parato- 

 mous Lime-haloide, and several others. In the same man- 

 ner have also been employed the adjectives axotomous, 

 diatomous, diprismatic, and prismatoidal, agreeably to the 

 explanations given above. The adjectives nndcavable and 

 native should be retained, only till the cleavage or the form 

 of those species to which they are now applied, will be as- 

 certained. Only a few, for want of better, have been taken 

 from colours, none from localities or persons, nor has, in 

 any instance, the adjective common been employed, which 

 is indeed the worst of alL The natural quality of the spe- 

 cies contained in the three first orders of the first class, 

 and in the second order of the third class, has produced the 

 necessity of deriving adjectives from other relations, which 

 would else not have been applied. 



. 239. REPRESENTATION OF THE SPECIES THROUGH 

 ITS DENOMINATION. 



The systematic denomination produces a repre- 

 sentation of the species. This nevertheless cannot 

 be substituted in the place of the character in the 

 Characteristic, nor of the general description in the 

 Physiography. 



It is not a small advantage of that systematic nomenda- 



