Argillaceous Genus. 79 . 



before roafting, but after that the martial part 

 is fallible. 



Green Clays. 



Some forts are faid to redden in fire, and 

 contain iron. Mr. Bergman has found fome 

 which contain copper and cobalt ; to feparate 

 which he precipitated the copper by iron, and 

 digefted the refiduum in diftilled vinegar. 

 Other forts are faid to contain nickel. 



Black Clays. 

 Thefe are faid to be bituminous. 



Variegated. 



The moft remarkable of this fpecies is the 

 Terra miraculofa Saxonitf, which is a beautiful 

 indurated clay, of a purplifh colour, with 

 white, yellow, red, or brown veins or dots. 



Bole. 



Is a term of uncertain fignification, and 

 fhould therefore be baniftied. Some beftow 

 this name on very fmooth compact clays, con- 

 fifting of the fineft particles : others require 

 befides, that their colour ihould be red, yel- 

 low, or brown, and that they fhould contain 

 iron. The recj generally blacken in fire, 2 



Bergm* 



