COAL. 617 



This is a modification of carbon which con- 

 tains, so little hydrogen as to yield no naphtha 

 or petroleum on distillation; whence it gives 

 neither flame nor smoke. 



a. Massive; with a conchoidal shining 



fracture of an aspect sometimes 

 nearly metallic. 



This occurs in Germany and other countries 

 among the primary rocks; in Staffordshire, 

 among the secondary coals. It passes into plum- 

 bago. 



b. Friable, pulverulent, or scaly. 



This variety is rare and in small quantity : it 

 occurs in Switzerland. 



c. Laminar : known by the name of blind 



coal, stone coal, culm, and Kilkenny 

 coal. 



This occurs, like the preceding, in the pri- 

 mary strata, in micaceous schist, argillaceous 

 schist, and gneiss. But it is far more abundant 

 in the secondary, as in many parts of Britain and 

 Ireland. It passes into common coal. 



d. Columnar, or rather prismatic. 



Occurs in the vicinity of trap rocks, and 

 is therefore partial and rare. It passes into 



