VI PREFACE. 



as this,, in numerous instances,, still remains dispu- 

 table and, on the other hand, there are substances, 

 which universal consent ranks with native fossils or 

 minerals, that undoubtedly originate from animal 

 and vegetal matter. It will perhaps, however, not 

 only be urged, that the proposed principle is insuf- 

 ficient for the purpose of division ; but, also, that 

 extraneous forms (as the mpdern school of minera- 

 logy calls the structure of petrifactions, &c. ) are not 

 to be considered as independent of their constituent 

 substances, but must be studied as mere modifica- 

 tions in the external characters of a mineral. Yet 

 it is evident, that if extraneous forms are to be at- 

 tended to at all, it is the/orw, and not the material 

 in which it occurs, that is the primary object of in- 

 vestigation; and this, in my humble opinion, lays the 

 foundation of a study, separate or distinct in its cha- 

 racter from that of mineralogy. Indeed, with all due 

 deference to the authority of Werner and his disci- 

 ples, I think it may be justly questioned, if the extra- 

 neous form ought to be numbered among the exter- 

 nal attributes of a mineral substance At least, it is 

 not an essential one (f), and of course can never, 



(/) That only can be called an essential attribute, in any 

 substance or species of matter, of which it cannot be deprived, 



