This section is from the "The New Student's Reference Work Volume 5: How And Why Stories" by Elinor Atkinson.
When you grow up and are very, very wise you will not say that iron rusts. You will say it becomes oxidized. That means that the surface of the iron is burnt by the oxygen of the air. Rust is really an iron ash. You can rub old rust off in a powder as fine as ashes. These iron ashes mix with the soil, giving it its good brown or red color. They dissolve in water, are taken up by plants and used to make their green color. Finally, through water and plants, we take iron into our bodies to give us the red color of our blood.
Isn't it a fine thing that iron can rust, or be burnt to a red ash by the oxygen of the air. Gold and silver do not rust, and so they are called the noble metals. But John Ruskin, a great English writer who thought the most useful things and men the noblest, said of iron: "It breathes the air, burns itself up in oxygen, and so gives its own life that we may live." If you see a rusty tack or nail, push it into the earth. It might give you a dangerous wound. But the earth can make the noblest use of it, and give it back to us in rippling grass and beating hearts.