They had passed near the old ovens, where in former times the coal merchants prepared charcoal. They stopped a bit there and the Chief Engineer explained to them how we make charcoal.
He told them that to make charcoal, you pack a lot of wood in an oven. The oven is covered with soil, so tight that the air cannot get in anywhere. Then, through a hole deliberately left, you light the packed wood.
Covered over, the oven burns slowly, at a low heat, and little by little the wood becomes charcoal.
—And the trees? asked Matthias.
—For the coal merchants it's the same as for the woodcutters, said the Engineer, they only cut the trees we tell them to cut, and in this way they don't damage the forest. The best thing is that most coal is obtained without cutting any trees. You find it in the ground. And I'm going to explain why.
“Thousands of years ago, forests were so dense that no animal could get in to graze.
“It was with great difficulty that the lions, bears and wolves, and the big birds with immense wings and steel talons, managed to live here.
“Each beast that could ate as much of the smaller ones in order to live. In the undergrowth the sun never penetrated. It was dark in broad daylight.
“These forests have aged and their trees have fallen onto the ground. Then the earth opened up due to earthquakes and natural disasters, and so trees were buried in very deep, extensive tombs.
“Over the years, other forests sprouted and grew up high just like the first ones then became old and fell. And the earth opened up and buried them. And again others grew.
“What became of these dead forests? They didn't disappear. Today, when we dig down very deep, we find them. They aren't trees as before. In the ground their wood has become coal, hard as stone and black as coal.
“And today, as men are so numerous and need huge fires for their work, they open the ground up and find as much coal as they want.
“With this you switch on machines, make factories run; railways and boats too. Imagine how many machines there are and how much coal they need.
“Who would have said that these dead trees would be useful after thousands of years! Well, that's the forest for you. It's good for man in a thousand ways, for long periods. It's inexhaustible; it lives and is useful for us, it dies and is useful for us.
“However, for the tree to give us as much wood as it does, it needs to live with thousands of other trees. Because like men, trees also live together, numerous, in places which are suitable for them, and they help each other.
“Together they fight against harsh winters and burning summers. Together they grow, develop great trunks and throw out strong branches.
“This way, high up in the mountains a large society is created, which we call a forest. This one!