STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 123 



known as brown coal. The terms, for the most part, are those in 

 popular use, showing that the distinction between the several mem- 

 bers is notable, (i) Gemeine Braunkohle, in more or less hard 

 masses, with or without trace of woody structure, brown to blackish 

 brown, with bright streak, dull fracture, breaks into irregular angu- 

 lar fragments, is intermediate between Erdkohle and Pechkohle; (2) 

 Erdkohle, earthy brittle, yellowish to dark brown, wholly amorphous, 

 much cleft by drying, alternating bright and dull laminae, the former 

 more common in the upper part of beds while the denser varieties 

 in the lower part of the bed give a shorter flame. The varieties 

 are very numerous ; Schwelkohle, very bituminous, resinous, yields 

 tar, illuminating gas and paraffin ; Schmierkohle belongs in the 

 upper part of beds and wdien damp feels like clay, Colnische umbra 

 is an earthly brown coal utilized as coloring material, Russkohle, 

 earthy, dusty, of irregular occurrence; (3) Lignit, masses of wood, 

 more or less fossilized, passes over into ordinary brown coal, is 

 yellow to dark brown and breaks like wood, may contain patches 

 of Erd-, Pech- and Glanzkohle, some lignits in drying become 

 Pechkohle. It is derived mostly from resinous trees, the stems 

 being flattened by softening and pressure. The varieties are nu- 

 merous; Bastko'hle forming layers or parts of layers, more or less 

 of bark structure belonging to Pinus, Taxiis, Alniis, etc., Nadel- 

 kohle, bundles of tissues of palms with parenchyma removed ; (4 

 and 5) Dysodil or Papierkohle and Blatterkohle, in very thin lami- 

 nae; (6) Moorkohle contains abundance of remains of swamp 

 plants as well as compressed woody roots, small stems, etc., usually 

 associated with deposits of lignit and occurs in the low^er portion 

 of the bed or fills spaces between the stems; (7) Pechkohle, dense, 

 more or less brittle, rather tender, breaks into sharp angular frag- 

 ments, black brown to pitch black, dull pitch-like to greasy luster 

 and irregular to conchoidal fracture, passes over to common brown 

 coal on one side or to Glanzkohle on the other ; sometimes it occurs 

 in Moorkohle, while at others it includes thin to 5-inch layers of 

 Glanz-, derived from conifer stems pressed flat; (8) Glanzkohle 

 is dense with conchoidal fracture, is blackish with greasy, vitreous 

 or metallic luster ; sometimes it forms whole beds but it is often as- 



