76o T. E. SAVAGE 



portions of tree trunks that lay at different angles and at different 

 levels from those that formed the bright bands in any exposure. 

 The distribution of the bright and dull laminae is not consistent 

 with this explanation. 



Microscopic examination of bituminous coal has shown that 

 spores are more numerous in the dull laminae than in the bright, 

 and hence some geologists have concluded that the dull laminae 

 resulted from the greater number of spores in these bands, while 

 the bright laminae were formed from the more woody portions of 

 the plants. However, a study of the dull laminae shows that, 

 while they may contain spores in greater abundance than the bright 

 laminae, yet they are very largely composed of mineral charcoal, 

 which certainly has been derived from plant tissues other than 

 spores. 



The alternation and great extent of the bright and dull laminae 

 are such constant features of the coal beds, and the mineral charcoal 

 is so generally present in the dull laminae, that any adequate 

 explanation of the origin of these features must involve agencies 

 that were repeatedly operative over practically the entire area of 

 accumulation of the coal beds. The only recurrent agency of 

 such widespread action is change in the water level of the basin 

 during the time the vegetable material was accumulating. 



If it is assumed that the dull laminae resulted from the flooding 

 of the basin, we should have associated with the dull laminae bands 

 of mud deposited during such times of flood. We are not left to 

 speculate with regard to the effects of flooding of the basin during 

 the progress of accumulation of the vegetable matter of the coal, 

 for we have such an example in the clay band or "blue band" of 

 the Herrin (No. 6) coal, which extends over practically the entire 

 area of its distribution, and is clearly a mud parting due to flooding. 

 Black shale partings, common in portions of some coal beds, as in 

 coal No. I, are also records of flooding of the coal-forming marshes. 

 The typical dull laminae and mineral-charcoal zones in the large 

 coal beds of Illinois, as elsewhere, are not such mud partings. They 

 usually contain only a slightly, if any, greater percentage of ash 

 than the bright bands and are practically free from clay silt. They 

 contain a relatively smaller percentage of volatile matter and a 



