I9I3.] STEVENSON— FORMATION OF COAL BEDS. 73 



cortex and the intra-cortical ftisain, which is finer than that from the 

 wood. 



Fayol'^ learned to distinguish coal made from Calaiiiodendron, 

 Cordaites or ferns as readily as he could distinguish a piece of 

 beech from one of fir. He recognized these types first in isolated 

 laminae, but afterwards in brilliant laminse occurring in the thickest 

 and purest parts of the Grande Couche. He saw tree trunks in 

 Commentry, some buried in the lower benches of the coal and others 

 passing from the coal into the overlying shale. One fourth of one 

 percent of the trees in the coal are vertical, an equal proportion are 

 inclined and the others are prostrate. Few trunks in coal are cylin- 

 drical ; where such stems occur, one can prove usually that one of 

 the extremities is in sandstone. 



David,'^ in describing deposits of Kerosene shale, reports that in 

 one mine at the end of Megalong ridge, the shale contains erect 

 stems of Vertehrdria; in another, prostrate stems ; in a third are 

 flattened stems or " barky casings of plants turned into bituminous 

 coal, over four inches in width." David saw many vertical and 

 prostrate stems of Vertehraria in the Shale at a locality in Cook 

 county. Wilkinson saw at Joadja creek impressions of Vertebraria 

 lying horizontally in the Kerosene shale as well as numerous vertical 

 stems of the same plant, whose lustrous, bright substance is in strik- 

 ing contrast to the dull luster of the enclosing shale. Nathorst 

 found stems of Bothrodendron in the Devonian coal of Bear island 

 and stems are present in many brown coal deposits as well as in the 

 peats of modern bogs. 



Foreign Bodies in Coal. 



The presence of tree stems in coal is normal ; but the coal often 

 contains what may be regarded as foreign bodies. 



Nodules of calcareous clay-iron stone are familiar objects in 

 coal beds as well as in the Coal Measures shales. They are from 

 mere specks to balls a foot or more in diameter. Occasionally they 



'''' H. Fayol, " fitudes," etc., pp. 135, 196, igS, 206, 207. 

 "T. W. E. David, Dept. Mines New South Wales, Rep. for 1890, 221-224; 

 C. S. Wilkinson, ibid., p. 208. 



