D4 CRITIQUES AND ADDRESSES. [v. 



and blacker, and more opaque, until it becomes impos- 

 sible to grind a section thin enough to be translucent; 

 while, on the other hand, in such as the " Better-Bed" 

 coal of the neighbourhood of Bradford, which burns with 

 much flame, the coal is of a far lighter colour, and trans- 

 parent sections are very easily obtained. In the browner 

 parts of this coal, sharp eyes will readily detect multi- 

 tudes of curious little coin-shaped bodies, of a yellowish 

 brown colour, embedded in the dark brown ground sub- 

 stance. 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 approxi- 

 mated ; 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 



