140 ON THE FORMATION OF COAL y 



dark brown ground substance. On the average, 

 these little brown bodies may have a diameter of 

 about one-twentieth of an inch. They lie with 

 their flat surfaces nearly parallel with the two 

 smooth faces of the block in which they are con- 

 tained ; and, on one side of each, there may be 

 discerned a figure, consisting of three straight 

 linear marks, which radiate from the centre of 

 the disk, but do not quite reach its circumference. 

 In the horizontal section these disks are often 

 converted into more or less complete rings ; while 

 in the vertical sections they appear like thick 

 hoops, the sides of which have been pressed to- 

 gether. The disks are, therefore, flattened bags ; 

 and favourable sections show that the three-rayed 

 marking is the expression of three clefts, which 

 penetrate one wall of the bag. 



The sides of the bags are sometimes closely 

 approximated ; but, when the bags are less 

 flattened, their cavities are, usually, filled with 

 numerous, irregularly rounded, hollow bodies, 

 having the same kind of wall as the large ones, 

 but not more than one seven-hundredth of an 

 inch in diameter. 



In favourable specimens, again, almost the 

 whole ground substance appears to be made up 

 of similar bodies more or less carbonized or 

 blackened and, in these, there can be no doubt 

 that, with the exception of patches of mineral 

 charcoal, here and there, the whole mass of the 



