A PIECE OF COAL. 173 
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 burnt plants, then ? Not burnt 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 afterwards 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 have still 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 near Newcastle, which I visited many years 
ago, you will see that we have very good evidence 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. 46) 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 gal- 
lery b, because a great deal of the coal in d has been 
already taken out. But we will stop in a because 
there we can see a great deal of the roof and the 
