. &17. CHARACTERISTIC. 879 



process, because in these bodies two of the most valuable 

 marks in the characters of solid minerals, form and hard- 

 ness, are wanting. They have not as yet been brought to 

 any degree of perfection ; and indeed there is little to 

 be done in this respect, our knowledge of their natural- 

 historical properties being still very defective. 



The specific characters should not contain either condi- 

 tioned or exclusive characteristic marks, though this may be, 

 and indeed is, the case with the characters of the orders 

 and the genera. In the latter characters there occur some- 

 times terms mutually excluding each other, as in the genus 

 Corundum, " Tessular, rhombohedral, prismatic^ or in the ge- 

 nus Iron-ore, " Streak red, brown. Mack." This evidently 

 means, that the forms of an individual belonging to the ge- 

 nus Corundum, must be either tessular, or rhombohedral, 

 or prismatic ; and that an individual of the genus Iron-ore 

 must yield a streak either red, or brown, or black ; because 

 in one and the same individual, two different kinds of the 

 same characteristic property are impossible. In another 

 place, an example will be given to shew, that characters 

 thus arranged do really convey all possible security ; which 

 example will at the same time serve to illustrate the use 

 of the Characteristic in this respect. 



. 247. NO CHARACTERISTIC BEFORE THE SYSTEM. 



The Characteristic presupposes in its full extent 

 the system, to which it refers. 



In the natural or synthetic system, or that whose foun- 

 dation is the natural-historical similarity, those objects are 

 placed nearest, which are connected by the highest degrees 

 of resemblance, or which are most similar to each other. 

 In arranging them, no attention is paid to single properties, 

 and perhaps least of all to such as might be useful in the 

 distinctive characters. Indeed, the conformity of the differ- 

 ent parts of the system would be very soon lost, should we 

 allow such accessory views to be introduced. First of all. 



