101 



■which shows it to contain some silex, and, perhaps, iron. 

 Coals are not known to crystallize, yet this glossy part in 

 many has a regular disposition towards it in the partings ; 

 and these mostly have the same angles, forming an upright 

 prism with rhomboidal bases, the angles of which are about 

 84° and 96°*. 



Tlie middle figure in this plate is a fragment of the New- 

 castle coal ; the completest crystal-like appearance J ever 

 saw. The upper surface is charcoaly, and it rests on a si- 

 milar substance, with irregular strata beneath. 



Newcastle coal loses about 35 per cent, of its weight while 

 flaming. 



Linnseus's description seems to belong to the more slaty 

 kind. 



The lower figure is from a piece of Scotch coal, which 

 was broke through the bituminous strata, in a transverse 

 direction : and shows the glossy fracture, with a sattiny ap- 

 pearance, as well as the angles of partings. This bitumi- 

 nous stratum is commonly somewhat shaly in this sort of 

 coal : the other part is mostly pure charcoal, and often ex- 

 hibits the shape of branches compressed, and the same 

 transverse contractions which take place in charring or 

 burning common deal. This coal loses 25 per cent, while 

 flaming, which it readily does, and continues its heat with 



* Most mixed coals in the common large masses break through the whole 

 stratum more or less in this form : these breaks or cracks are called backs, 

 cutters, and partings, by the miners. 



