108 ILLINOIS ACADEMY OF SCIENCE 



The analyses given in Table I. show that the mineral char- 

 coal contains a smaller percentage of volatile matter and a 

 larger percentage of fixed carbon than the average coal of the 

 same bed. The proximate analyses (Table II.) of the bright 

 and dull laminae of the bituminous coal bed, cited by Pringle 1 

 indicates that the dull laminae are similar in composition to 

 mineral charcoal, as regards the smaller percentage of volatile 

 matter, and the larger percentage of fixed carbon compared 

 with the bright or the average coal. 



Table II. 



Volatile Fixed 



Water Matter Carbon Ash 



Dull laminae 1.68 14.71 77.17 6.44 



Bright laminae 1.75 31.63 63.96 2.66 



Lesquereaux 2 described the changes that occur in the veget- 

 able matter at the surface of swamps during dry periods as 

 follows : 



'Wherever the growth of peat in submerged bogs is checked by 

 dryness or other causes, the upper surface of the peat becomes 

 crusted, hardened and transformed into a thin coating quite im- 

 pervious to the entrance of any kind of foreign matter, and it is 

 upon this hard upper crust that the boggy humus forms, or whenever 

 the land becomes resubmerged, a new peat vegetation begins. In 

 such cases such a crust remains as a parting between two layers of 

 peat." 



Von Gumbel in 1883 suggested : "It is very probable that in 

 occasional drying of the/swamp, followed by renewal of flood- 

 ing, lies the explanation of the alternating bright and dull coal 

 bands." 



In discussing the progress of putrefaction of the vegetable 

 matter of coal, as described by Renault, David White 3 says that 

 if uninterrupted, the process of putrefaction goes on until all 

 the softer tissues are disintegrated and decomposed, leaving 

 only the most indestructible parts, immersed in a dark subgela- 

 tinous, plastic or liquid mass, the fundamental matter. This 

 fundamental matter not only envelops the undestroyed woody 

 matter, but it infiltrates the surviving tissues to a greater or 

 less extent. Where the impregnation is complete, we find 

 dense, glossy, and shining coal. In many instances the im- 

 pregnation has been imperfect, and sometimes intergrades to 

 a charcoal or "mother coal." 



It is thought by the writer that the oft-repeated lowering, 

 probably of only a very few inches, of the water level in the 



1. Pringle, John. Trans. Edinburgh Geol. Soc, vol. 10, pt. 1, 1912, p. 33. 



2. Lesquereaux, L. Second Geol. Survey of Penna. Ann. Rept. for 1885, p. 118. 

 3 White, David. Some Problems in the Formation of Coal, Econ. Geology, 



Vol. 3, 1908, p. 303. 



