SEVENTH ANNUAL MEETING 105 



ferns 1 in the midst of the mineral charcoal fragments; (4) the 

 absence of layers of ash that would result from the burning of 

 vegetable matter at the surface of the bog; and (5) the changes 

 that take place in the vegetable matter at the surface of shallow 

 marshes during period of drought and exposure at the present 

 time. 



EXPLANATION OF THE BRIGHT AND DULL LAMINAE 



In explaining the origin of the bright and dull laminae, 

 Dawson 3 maintained that it was only the outer bark of flattened 

 tree trunks that formed the shining coal. In a recent paper on 

 the origin of bright laminae of coal, Pringle 3 of the Geological 

 Survey of Great Britain, reaffirms Dawson's view. 



The serious objection to this view is the fact that the bright 

 and dull laminae of the coal beds are so nearly parallel and are 

 often continuous for long distances. Trees that are overturned 

 in swamps fall in various directions, and their trunks lie across 

 one another at different angles. If only the cortical portion 

 of tree trunks formed the bright laminae of coal, these bright 

 laminae would not be continuous for long distances, and the 

 dull laminae would be broken at short intervals by small areas 

 of bright coal representing the cross-sections and oblique sec- 

 tions of the cortical portions of tree trunks that lay at different 

 angles and at different levels from those that formed the bright 

 bands in any exposure. 



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 re- 



1, White, David; Economic Geology, Vol. III., 1908, p. 302. 



2, Dawson, J. W. ; On the Conditions of the Deposition of Coal. Quar. Jour. 

 Geol. Soc, Vol. 22. 1866, p. 141. .„,«.,. , r> , ^ c-j- 



3, Pringle, John; On the Origin of Bright Laminae of Coal. Trans. Edin- 

 burgh Geo.. Soc. Vol. X., pt. 1, 1912, p. 33. 



