GENERAL DESCRIPTION OF THE SPECIES. 251 



words and expressions should uniformly be adopted, when not in- 

 consistent with an easy comprehension of their meaning. 



Descriptions are required, whenever there occur new varie- 

 ties of a species which is either already known, or entirely new ; 

 they are also useful in such varieties as are distinguished by a par- 

 ticular application, or any remarkable property, or such as have 

 been provided with particular names in the arts of life. In these 

 last instances it is only requisite to indicate those properties, by 

 which the variety in question differs from other varieties of the same 

 species. It is also very useful to give an accurate description of 

 such varieties as are subjected to a chemical analysis. 



<. 125. GENERAL DESCRIPTION OF THE SPECIES. 



In representing the species in the mineral kingdom, it is 

 necessary to construct a Collective, or General Description. 



The problem to be resolved in constructing a General Description 

 is, to give a correct idea of all, or at least of the known varieties of 

 a species, in their proper connexion ; it must therefore contain at 

 once all the descriptions of these varieties without its being itself, 

 in a strict sense, a description at all. It is evident, that the only 

 means of arriving at this end, will be the employment of the series 

 of characters. 



The method of constructing a general description t>f a species is 

 as follows. First, any suitable variety of the species is chosen, and 

 described with all possible accuracy, the single characters succeed- 

 ing each other agreeably to the order fixed upon, as abovemen- 

 tioned. The description will contain only single characters, con- 

 sisting of a certain form, a certain color, a certain kind of lustre, 

 a certain degree of hardness or of specific gravity, &c., all of these 

 being members of their respective series. If, in the place of every 

 one of these single characters, we substitute the complete series to 

 which it belongs, the Description of the Individual, or of the va- 

 riety, is transformed into the Collective or General Description of 

 the Species 



The characters contained in the general description are expressed 

 in series, produced either by immediate observation, or by deriva- 

 tion. The characters in the descriptions of determined varieties 

 consist of single members of these series. Evidently, the col- 

 lective description not only produces a complete idea of the spe- 



