148 CHARACTERISTIC. 



be the next superior idea of the system.) The shorter the charac- 

 ter is, the more facility and certainty will it afford in the distinction; 

 hence characters should be so constructed as not to contain any thing 

 but what is required for the evidence and distinction of the species. 



. 120. CHARACTERS OF THE CLASSES AND ORDERS, 



The characters for the classes and orders in the analyt- 

 ical system are formed by the distribution in producing the 

 system, and consist of single marks. 



In this system, minerals are formed into classes from the folio w- 

 ing considerations; viz. crystallized minerals, semi-crystallized min- 

 erals, and uncrystallized minerals. (. 109.) Now the characters of 

 the classes are, for the first class, "minerals crystallized;" for the 

 second, "minerals semi-crystallized;'* and for the third, "minerals' 

 uncrystallized." But these, it is obvious, are the grounds upon 

 which our division of minerals into classes is founded. The charac- 

 ter, moreover, for each of the classes, consists of a single character- 

 istic mark. The same is true as respects the orders, the characters 

 of which depend upon the same property as w r as employed for their 

 formation, and as these divisions are formed upon single properties, 

 so fne cnarSctefs for the orders will consist of sfngi'e terms-. 



In the natural classification of the mineral kingdom, single char- 

 acteristic terms cannot be employed, as nothing short of a compound 

 character is nere found sufficient for a general distinction. It is in. 

 this respect, in particular, that the analytical method has the advan- 

 tage in practice. 



. 121. CHARACTERS FOR THE SPECIES. 



The characters for the species must be so arranged as to 

 effect the determination of individuals in the most sure man- 

 ner, of which the science is capable. 



For this reason, the species in each of the orders, excepting the 

 two last of the uncrystallized class, are arranged in an order depend- 

 ing upon their degrees of hardness; and have this property given as 

 the first term in their characters. But hardness, by itself, is insuffi- 



