OF THE CLASSIFICATORY SCIENCES. 315 



the establishment and use of External Characters, especially of Crys- 

 talline Forin^ 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 Systems ; 

 both those in which chemical methods of arrangement -are adopted, and 

 those which profess to classify by the natural-history method. 



