484 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



branch is found, which has been changed in one portion into clean, 

 compact coal, while in the other it has become fusain. 



Aside from shaly seams, the coal usually has from 6 to 8 per 

 cent, of ash, yields 6o to 62 per cent, of bright coke and gives off gas 

 burning with brilliant flame. Analyses by Regnault and by Carnot 

 give the ultimate composition : 



Cannel is of common occurrence in the Grande Couche as thin 

 streaks or as lenses, which sometimes extend hundreds of meters ; 

 it yields a brilliant gas and has from 33 to 58 per cent, of carbon. 

 Fayol seems to be inclined to believe that difference in character of 

 coal may be related in some way to the ash-content ; ordinary coal 

 has 5 to 10, cannel, 7 to 12 and boghead 25 to 50 per cent, of ash. 



Trunks, branches, etc., are in rocks of all kinds ; are usually pros- 

 trate, but some are inclined, others erect. There are few in con- 

 glomerates, ten times as many in sandstones, 200 times as many in 

 shales and 1,000 times as many in coal. Erect stems are rare in coal 

 and shale, proportionately they are most numerous in the coarser 

 rocks. At one locality, Fayol found a fern stem inverted. Attached 

 branches are rare but many stems retain their roots. Still, the most 

 of them have neither roots nor branches ; but there are stumps re- 

 taining roots spread out on the underlying deposit, which they do not 

 penetrate. One such stump, with diameter of one meter, showed 15 

 Stigmaricu radiating from it and enclosing a space of about 400 

 square feet. These Stigmaricc are arranged regularly and are flat- 

 tened. Stems of trees, numerous in the coal, are compressed, the 

 interior portions having disappeared, the rind only remaining, con- 

 verted into coal. 



The roof is of ordinary carbonaceous or bituminous shale, pass- 

 ing upward gradually into sandstone. Commonly it is rich in plant 

 remains. The floor is usually carbonaceous shale, but occasionally 

 sandstone, and the passage to the coal is gradual. There are many 

 cases of contemporaneous erosion. One in the Tranchee de Foret 



