Everything that men need, that is for their use—all that is prepared by the sun, and on all that goes much sun’s heat. The reason that men need bread is because the sun has produced it, and because there is much sun’s heat in it. Bread warms him who eats it.
The reason that wood and logs are needed is because there is much heat in them. He who buys wood for the winter, buys sun’s heat; and in the winter he burns the wood whenever he wants it, and lets the sun’s heat into his room.
When there is heat, there is motion. No matter what motion it may be—it all comes from heat, either directly from the sun’s heat, or from the heat which the sun has prepared in the coal, the wood, the bread, and the grass.
Horses and oxen pull, men work—who moves them?—Heat. Where does the heat come from?—From the food. And the food has been prepared by the sun.
Watermills and windmills turn around and grind. Who moves them?—Wind and water. And who drives the wind?—Heat. And who drives the water?—Again heat. Heat raises the water in the shape of vapour, and without this the water would not be falling down. A machine works—it is moved by steam. And who makes steam?—Wood. And in the wood is the sun’s heat.
Heat makes motion, and motion makes heat. And both heat and motion are from the sun.