Reflections on some Mlneralogical Systems* 4 1 7 



idea of certain exclusive properties. Silica is not the only 

 substance which in its aggregation can acquire extreme hard- 

 ness ; there are other earths which can become harder than 

 it : an aggregate of alumine surpasses it in thi* respect, as 

 we see in sapphire. And what shall we say of the dia- 

 mond ? Most assuredly we shall not consider it, like a cele- 

 brated German who said to me, when I made some ob- 

 jections to him on the place which he assigned (his fossil 

 and the new discoveries respecting it ; ie And who will tell 

 me that carbon is not also an earth ?" 



DIAGNOSTIC OR DESCRIPTIVE MINERALOGY 



We shall now proceed to the second part of mineralogy; 

 to the means which assist us in the diagnosis or art of know- 

 ing minerals. This will comprehend the art of making 

 them known to others, or that of describing them. 



M. Werner has divided the diagnostic characters into, 

 1st, external characters ; 2(1, chemical or internal characters; 

 3d, physical characters; and, 4th, empirical characters. 

 Perhaps it may surprise some to see the latter epithet thus 

 confined to only a part of this system. 



The preference given by M. Werner to external charac- 

 ters is manifest from what follows : (Brochant, Introduc- 

 tion, p. 30.) He examines these characters corresponding 

 to the five following questions : " What are the characters 

 which always manifest themselves, and in all minerals? 

 These are the external characters and the chemical charac- 

 ters, although thesmallness of the specimens often prevents 

 the latter from being discovered. (Is there not here a little 

 contradiction in the characters which always manifest them- 

 selves, and that often cannot be discovered ?)— What are 

 those which most certainly indicate an essential difference ? 

 The chemical characters; nevertheless, the external charac- 

 ters equally indicate the state of aggregation — What are 

 those which we can determine more exactly ? The external 

 characters, because the others require delicate operations. — 

 What are the most easily and most promptly found ? The 

 external characters, because they immediately strike our 

 senses. — What arc those which we can discover without 

 destroving the mineral ? The exterrial characters." 



M. Werner principally employs but two chemical cha- 

 racters; fusibility bythe blow-pipe, and the proof of acids. 

 The physical properties which he mentions are electricity, 

 magnetism and phosphorescence, with their modifications; ^ 

 and even the indication of these characters has no other ob- 

 ject but to complete the description of the minerals. In the 



Vol. 30. No. 1S2. Dec. 1810. 2 D art 



