618 COAL. 



plumbago, forming the anthracolite of Baron 

 Born. 



B. Flaming, and burning easily; with smoke. 

 Common coal. 



It occurs either massive or slaty ; but the two 

 are so generally united, that it is unnecessary to 

 distinguish them as separate varieties. It differs 

 much in quantity in different situations ; chiefly 

 in consequence of the degree in which it recedes 

 from the preceding, or the quantity of bitumen 

 which it yields on distillation. The best kinds 

 unite, or cake, in the fire, by a partial fusion. 

 It presents other varieties of much inferior value, 

 in consequence of mixtures of clay, forming 

 coarse coal. These pass into bituminous shale, 

 formerly noticed. They are always secondary. 



C. Very inflammable: leaving* little coak after 

 inflammation; massive or imperfectly laminar: with a 

 large conchoidal fracture more or less bright, but 

 sometimes quite dull. Cannel coal and Parrot coal. 



Occurs in the secondary coal of other quali- 

 ties, and is sometimes wrought, like jet, for orna- 

 ments. 



D. Coak, ashes, and smut. These rare and par- 

 tial modifications occur in the vicinity of trap, as already 

 noticed* 



