214 HISTORY OF MINERALOGY. 



and the knowledge which has reference to the 

 classification will be precise as far as this process is 

 precise, and vague as far as this is vague. 



There must be, then, as a necessary supplement 

 to Chemistry, a Science of those properties of bodies 

 by which we divide them into kinds. Mineralogy 

 is the branch of knowledge which has discharged 

 the office of such a science, so far as it has been 

 discharged ; and, indeed, Mineralogy has been gra- 

 dually approaching to a clear consciousness of her 

 real place, and of her whole task ; I shall give the 

 history of some of the advances which have thus 

 been made. They are, principally, the establish- 

 ment and use of external characters, especially of 

 Crystalline Form, as a fixed character of definite 

 substances; and the attempts to bring into view 

 the connexion of chemical constitution and external 

 properties, made in the shape of mineralogical Sys- 

 tems ; both those in which chemical methods of 

 arrangement are adopted, and those which profess 

 to classify by the natural-history method. 



