THE VEGETABLE MATTER OF ILLINOIS COAL BEDS 757 



make up nearly or quite one-half of the coal beds, and they appear 

 to be of the same general nature as the bedding planes mentioned 

 above. They are often rather uniform in thickness over consider- 

 able areas, but in places they thicken for some distance and in 

 others they thin down to knife-edge partings. The bright laminae 

 appear to be rather homogeneous in structure; but where the coal 

 is spHt along well-developed dull laminae the cleavage planes almost 

 always show distinct mineral charcoal surfaces. A typical dull 

 lamina appears to be composed of a film of dull, structureless coal 

 at the top, which passes downward into coarse-textured, fibrous, 

 mineral charcoal in the middle part, and this, in turn, grades down- 

 ward into a film of dull, structureless coal below. 



The features above described are not peculiar to Illinois coals. 

 H. S. Rogers and others have noted the alternations of laminae of 

 bright and dull coal, and the predominance of mineral charcoal in 

 the dull laminae, in the coals of the Appalachian region, and the 

 writer has observed the same characteristics in the coals of Iowa. 

 They have been described from coal beds generally in different 

 parts of the world. The mineral charcoal is so constantly present, 

 and so intimately mingled in, and constitutes such an important 

 part of, the dull laminae of the coals of Illinois that they must have 

 been developed together, and a satisfactory explanation of the one 

 must also explain the other. 



THE "mother coal" OR MINERAL CHARCOAL 



Two main explanations have been proposed to account for the 

 origin of mineral charcoal. One of these, held by many paleo- 

 botanists and chemists in recent times, explains the mineral char- 

 coal as formed from charred plant tissues resulting from forest 

 fires sweeping over land areas, the charred fragments being sub- 

 sequently swept by flooded streams into the basins, where they were 

 deposited with the mass of vegetable matter there in process of 

 accumulation. 



This explanation assumes that a considerable part of the vege- 

 table matter of the coal was transported material, which assumption 

 is open to all of the objections to the transport theory mentioned 

 above. It assumes that a very important proportion of the coal 



