On Crystallography. '^67 



these nam^s on their memory, by connecting them with 

 considerations which arc easily classified in the mind. 

 They will perceive that, by a kind of oeconomy of language^ ' 

 extremely useful in such eases, the same name is frequently 

 apphcable to varieties taken in different species. It is true- 

 that on one hand the word which serves to designate such 

 a variety might also serve another variety of the same 

 species. For example : I denoniinaie binary^ a form which, 

 depends on a decrement by two ranges. Now supposing 

 this decrement to take place on the edges, it is possible, 

 that another variety of the same substance may be owing 

 to a decrement vvhich takes place by two ranges on the 

 angles. But in this case the system will present for the- 

 latter another name borrowed from adiBercnt consideration* 

 The inconvenience just mentioned is common to all no- 

 menclatures, and seems unavoidable. Thus, in the language 

 of botany, one variety will bear ihe name of crassijolia, or 

 of rot undi folia, while another variety of the same species 

 shares with the first the character which has served to di- 

 stinguish it. The essential requisite is, that the method 

 should be copious enough to furnish at least to all the 

 known wants of science. I even expect'that, by means of 

 the labour I have performed, a great part of the forms which 

 "shall be discovered in future will be found to have been 

 named bef-)rchand ; and as to those which require new 

 names, we shall have at least a system from which to de- 

 signate them. In all descriptions of researches, it becomes 

 easier to go forward when the route is traced. 



Principles of the nomenclnitLve, — The primitive form of 

 any given substance is alwavs designated by the word pri- 

 mitive added to the name of the species. Examples : — 

 primitive zircon, primitive carbonated lime, primitive sul^ 

 pluirated lime, &c. 



We may consider secondary forms : — 

 J . With respect to the modifications of the primitive form, 

 when the faces of the latter are combined with - 

 those which result from the laws of decrement. 



2. By themselves, and as purely geometrical forms. 



3. With respect to certain facets or certain ridges remarka* 



ble by their assortment or their positions. 



4. With respect to the laws of decrements on which they 



depend. 



5. With respect to the geometrical properties which they 



present, 

 p. Finally, with respect to certain particular accidents, 



|-. Secondary 



