as a Branch of Natural History^ S^c, 231 



§ 36. But there is another way of judging of the importance 

 of characters, which, although rather of an empirical nature in 

 the present state of the science, is nevertheless very useful, as 

 throwing a new and essential light on the subject. Though the 

 nature and the cause of the connection existing between the 

 chemical composition and the physical properties of minerals is 

 quite unknown, experience has often taught us that such a con- 

 nection really exists. Nothing shows more clearly this fact, 

 than observing the same minerals assembled close to one another, 

 in two methods so entirely dissimilar as to their principles, as 

 that of Mohs, and the last arrangement of mineral substances ac- 

 cording to their electro-negative elements of Berzelius. The very 

 same minerals which in Mohs's system, founded entirely on 

 physical characters, to the complete exclusion of chemical com- 

 position and chemical properties, are assembled in the orders 

 Erze (ores), Metalle (metals), Kiese (pyrites), Glanze (glances 

 or galenas) ; are also found joined together in the simple 

 metals, and in the families Sulphur and Oxygen of Berzelius's 

 arrangement, founded solely on chemical composition. Now, 

 in such a case, the physical characters common to all the mem- 

 bers of such chemical groups, will be more important than the 

 more particular or individual ones ; and at the same time, the 

 chemical element common to the composition of the members of 

 each of these groups will be considered more important, and the 

 chemical or mineralogical character, by which the presence of 

 this element is denoted, of greater value, than the elements 

 which belong only to one or to a few of the members of the 

 same groups. It is by means of such considerations that the 

 greater importance of the electro-negative element in the com- 

 bination over the electro-positive will be established ; and in this 

 way the chemical characters which indicate the presence of the 

 electro-negative element, as well as the physical ones, such as 

 nature and degree of lustre, of translucidity, of hardness, which 

 appear to hold some connection with that element, will be 

 reckoned more valuable than the specific gravity, the colour, 

 and in some cases the variety of crystalline form, which seera 

 rather more connected with the base or electro-positive ele- 

 ment of the substance. These instances will be sufficient for 

 our present purpose, which is not to dwell on details, but 



