NOME XIV. SHALE AND COAL. 



NOME XIV. SHALE AND COAL. 



The particles of shale sometimes pass into 

 coal, or the reverse. But this may rather be 

 regarded as an adherence. Sometimes the shale 

 is marked with vegetable impressions, which like- 

 wise pass into the coal. 



Coal is sometimes, however, found so impure 

 as to be unfit for domestic purposes; and such 

 mines are commonly abandoned. When in the 

 mineralogic language it passes into slate, it is 

 far from being a recommendation in the kitchen 

 or in the parlour. 



The passage of coal into bituminous shale, is 

 the most interesting. The latter sometimes 

 bears the impressions of fish ; which never seem impressions, 

 to be observable on the coal. But Mr. Jameson 

 says that the fish themselves are generally con- 

 verted into coal, sometimes the scales into cop- 

 per-ore; bituminous shale being common in 

 copper-mines. It is the slate-clay, Schieferthon 

 \ of Werner, which generally accompanies coal, 

 and presents vegetable impressions, chiefly of 

 gigantic ferns and reeds now only found between 

 the tropics. This substance is commonly soft; 

 but is sometimes so hard as to resemble basanite. 



