But how is it that a gum-tree forest is kept up, for there must be a tremendous lot of lime, soda, flint, and the rest, removed from the soil?
Yes, but when the trees fall, they rot, and the solid parts return to the ground.
Oh, father, the remains are very small, compared to the living tree.
True, because the principal part of a plant consists of the gases, which fly off, and of carbon, which unites with the oxygen of the air.
How does God bring fresh carbon to the forest?
Several ways: smoke is one source, and the breath of animals another.
What has the breath to do with it?
Every time you respire, or breathe out, some carbonic acid comes out with air, and is carried into the atmosphere.
Why, father, you do not mean to say that my breath helps to make cabbages grow.
The carbon passing from your body may become a part of a cabbage, or gum tree, or a delicate tulip.