BITUMINOUS COALS 193 



they represent only small fragments or chips of the same. The 

 thin strips of "bright coal," therefore, are also anthraxylon com- 

 ponents. 



Origin of the small anthraxylon components. — -It is interesting 

 to know why so large a bulk of the coal should exist in the shape 

 of these thin but relatively wide or broad anthraxylon chips. This 

 question is readily and satisfactorily answered by analogous condi- 

 tions in peat. Furthermore, a study of these chips of wood in 

 peat lends at once, by analogy, a proof of the woody origin of the 

 anthraxylon components in coal and form a picture as to what may 

 have taken place in the peat bogs of the Coal Age. 



In examining a peat deposit such as had its origin in an arboreal 

 growth (Fig. 13), it is discovered that a large proportion of the 

 woody matter consists of thin scaly chips, as shown in Figure 14, 

 which may easily be separated from the peat. As shown in 

 Figure 15, they consist of very thin tangential shells and thin 

 radial plates. 



The larger stems and branches of the fallen trees while still 

 above the surface of the deposit become partially decayed. The 

 tissues, having thus become very much weaker along the spring 

 wood of the annual growth rings where the cells are large and the 

 walls relatively thin, are apt to separate along this area, peeling 

 off as thin tangential sheets at the slightest disturbance. A semi- 

 decayed stem of the basswood, Tilia Americana, is a well-known 

 example with a tendency to peel off in this way. Sheets of semi- 

 decayed wood of that nature break up very readily into smaller 

 and still thinner chips. Conifers also have a tendency to peel off 

 in this manner. In trees with broad rays like the oak, the weakest 

 areas are formed along planes parallel to the medullar}' rays and 

 the tissues will separate into thin radial plates instead of tangential 

 scales or shells. Through either mode of disintegration numerous 

 thin and relatively broad plates or scaly chips of semi-decayed wood 

 are formed. These constitute a very large proportion of the peat. 

 A similar mode of disintegration must have taken place in the peat 

 stage of the Paleozoic coals, as the small anthraxylon chips in 

 coal indicate. The chips in coal and the chips of woody peat 

 in peat are similar. 



