But sooner or later someone discovered a way of starting a fire. The oldest way we know about is rubbing two dry sticks together. Later came striking sparks from stones, and using a burning glass. Today we can start a fire easily with matches or electric sparks.
Scientists tell us that when any substance burns it unites with oxygen, one of the gases in the air. Something is always left in place of a substance that burns up. But we do not always see this something. When wood burns, for instance, the wood disappears. A few ashes are left. But most of the wood has been changed to invisible water vapor and carbon dioxide.
Think of eating raw meat. Living in unheated houses. Doing without automobiles and airplanes. The very suggestion makes us realize how hard it would be to get along without fire. But fire can also be a terrible enemy if it gets beyond control. Every year it does millions of dollars worth of damage and costs a great many lives.
