A PIECE OF COAL. 
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which you can pick for yourself out of the coal- 
scuttle. Our work to-day is to relate the history of 
this black lump ; to learn what it is, what it has been, 
and what it will be. 
It looks uninteresting enough at first sight, and yet 
if we examine it closely we shall find some questions 
FIG. 47. Piece of coal, a, Smooth face, showing laminae of 
thin layers. 
to ask even about its appearance. Look at the smooth 
face of this specimen and see if you can explain those 
fine lines which run across so close together as to 
look like the edges of the leaves of a book. Try to 
break a piece of soft coal, and you will find that it will 
split much more easily along those lines than across 
the other way of the lump; and if you wish to light 
a fire quickly you should always put this lined face 
downward so that the heat can force its way up 
through these cracks and gradually split up the 
block. Then again if you break the coal carefully 
along one of these lines you will find a fine film of 
charcoal lying in the crack, and you will begin to sus- 
pect that this black coal must have been built up 
