176 THE FAIRY-LAND OF SCIENCE. 
in very thin layers, with a kind of black dust between 
them. 
The next thing you will call to mind is that this 
coal burns and gives flame and heat, and that this 
means that in some way sunbeams are imprisoned in 
it; lastly, this will lead you to think of plants, and 
how they work up the strength of the sunbeams into 
their leaves, and hide black carbon in even the purest 
and whitest substance they contain. 
Is coal made of burned plants, then ? Not burned 
ones, for if so it would not burn again; but you may 
have read how the makers of charcoal take wood and 
bake it without letting it burn, and then it turns black 
and will afterward make a very good fire; and so 
you will see that it is probable that our piece of 
coal is made of plants which have been baked and 
altered, but which still have much sunbeam strength* 
bottled up in them, which can be set free as they 
burn. - 
If you will take an imaginary journey with me to 
a coal-pit you will see that we have very good evi- 
dence that coal is made of plants, for in all coal- 
mines we find remains of them at every step we 
take. 
Let us imagine that we have put on old clothes 
which will not spoil, and have stepped into the iron 
basket (see Fig. 48) called by the miners a cage, and 
are being let down the shaft to the gallery where the 
miners are at work. Most of them will probably be 
in the gallery b, because a great deal of the coal in 
a has been already taken out. But we will stop in a 
because there we can see a great deal of the roof and 
